stm32f4 __wfi

Christian Mauderer christian.mauderer at embedded-brains.de
Wed Apr 24 08:48:50 UTC 2019


There is the wfi in the Idle body. So as soon as all your tasks are
sleeping (via sleep(), rtems_task_wake_after(), waiting for some signals
or similar functions) wfi will be called.

Note that there most likely is a lot of potential in the drivers to save
power. Also note that the system will wake up every tick. So depending
on your configuration the power consumption will vary.

Am 24.04.19 um 10:44 schrieb Jython:
> i searched it by add -i 
> 
> 56794:0000d040 <_CPU_Thread_Idle_body>:
> 56795-#ifdef ARM_MULTILIB_HAS_WFI
> 56796-
> 56797:void *_CPU_Thread_Idle_body( uintptr_t ignored )
> 56798-{
> 56799-  while ( true ) {
> 56800-    __asm__ volatile ("wfi");
> 56801-    d040:    bf30          wfi
> 56802-  }
> 56803:    d042:    e7fd          b.n    d040 <_CPU_Thread_Idle_body>
> 56804-
> 56805-0000d044 <rtems_filesystem_default_close>:
> 56806-int rtems_filesystem_default_close(
> 56807-  rtems_libio_t *iop
> 56808-)
> 56809-{
> 56810-  return 0;
> 56811-}
> 56812-    d044:    2000          movs    r0, #0
> 56813-    d046:    4770          bx    lr
> 
> 
> that's to say when i want to enter low power  i just need to call sleep
> or rtems_task_wake_after or just while(1); ?
> 
> On Wed, Apr 24, 2019 at 4:36 PM Christian Mauderer
> <christian.mauderer at embedded-brains.de
> <mailto:christian.mauderer at embedded-brains.de>> wrote:
> 
>     For some reason your grep hasn't found the _CPU_Thread_Idle_body. It's
>     possible that the stm32f4 uses some other function for that also I don't
>     know why.
> 
>     For example for the xilinx_zynq_a9_qemu BSP the disassembled idle body
>     looks like follows:
> 
>     void *_CPU_Thread_Idle_body( uintptr_t ignored )
>     {
>        11d70:       b480            push    {r7}
>        11d72:       b083            sub     sp, #12
>        11d74:       af00            add     r7, sp, #0
>        11d76:       6078            str     r0, [r7, #4]
>       while ( true ) {
>     #ifdef ARM_MULTILIB_HAS_WFI
>         __asm__ volatile ("wfi");
>        11d78:       bf30            wfi
>        11d7a:       e7fd            b.n     11d78
>     <_CPU_Thread_Idle_body+0x8>
> 
>     Am 24.04.19 um 10:25 schrieb Jython:
>     > arm-rtems4.11-objdump -dS hello.exe | grep idle --color=auto -n -B
>     5 -A 12
>     >
>     > there is no idle function which calls wfi command
>     > // log
>     > 508-       
>     > 509-       
>     > 510-               
>     > 511-    }
>     > 512-   
>     > 513:    if((*USART2_SR) & (1<<4))  // idle
>     > 514-     3aa:    4b13          ldr    r3, [pc, #76]    ; (3f8
>     > <USART2_handler+0x94>)
>     > 515-     3ac:    681b          ldr    r3, [r3, #0]
>     > 516-     3ae:    681b          ldr    r3, [r3, #0]
>     > 517-     3b0:    f003 0310     and.w    r3, r3, #16
>     > 518-     3b4:    2b00          cmp    r3, #0
>     > 519-     3b6:    d00a          beq.n    3ce <USART2_handler+0x6a>
>     > 520-    {
>     > 521:        //printk("idle ");
>     > 522-       
>     > 523-        temp = (*USART2_SR);
>     > 524-     3b8:    4b0f          ldr    r3, [pc, #60]    ; (3f8
>     > <USART2_handler+0x94>)
>     > 525-     3ba:    681b          ldr    r3, [r3, #0]
>     > 526-     3bc:    681b          ldr    r3, [r3, #0]
>     > 527-     3be:    60fb          str    r3, [r7, #12]
>     > 528-        temp = (*USART2_DR);
>     > 529-     3c0:    4b0f          ldr    r3, [pc, #60]    ; (400
>     > <USART2_handler+0x9c>)
>     > 530-     3c2:    681b          ldr    r3, [r3, #0]
>     > 531-     3c4:    681b          ldr    r3, [r3, #0]
>     > 532-     3c6:    60fb          str    r3, [r7, #12]
>     > 533-        //temp = temp;
>     > --
>     > 627-       
>     > 628-       
>     > 629-               
>     > 630-    }
>     > 631-   
>     > 632:    if((*USART3_SR) & (1<<4))  // idle
>     > 633-     44c:    4b12          ldr    r3, [pc, #72]    ; (498
>     > <USART3_handler+0x8c>)
>     > 634-     44e:    681b          ldr    r3, [r3, #0]
>     > 635-     450:    681b          ldr    r3, [r3, #0]
>     > 636-     452:    f003 0310     and.w    r3, r3, #16
>     > 637-     456:    2b00          cmp    r3, #0
>     > 638-     458:    d00a          beq.n    470 <USART3_handler+0x64>
>     > 639-    {
>     > 640:        //printk("idle ");
>     > 641-       
>     > 642-        temp = (*USART3_SR);
>     > 643-     45a:    4b0f          ldr    r3, [pc, #60]    ; (498
>     > <USART3_handler+0x8c>)
>     > 644-     45c:    681b          ldr    r3, [r3, #0]
>     > 645-     45e:    681b          ldr    r3, [r3, #0]
>     > 646-     460:    60fb          str    r3, [r7, #12]
>     > 647-        temp = (*USART3_DR);
>     > 648-     462:    4b0f          ldr    r3, [pc, #60]    ; (4a0
>     > <USART3_handler+0x94>)
>     > 649-     464:    681b          ldr    r3, [r3, #0]
>     > 650-     466:    681b          ldr    r3, [r3, #0]
>     > 651-     468:    60fb          str    r3, [r7, #12]
>     > 652-       
>     > --
>     > 26329-
>     > 26330-    if (newTail == tty->rawOutBuf.Head) {
>     > 26331-      /*
>     > 26332-       * Buffer has become empty
>     > 26333-       */
>     > 26334:      tty->rawOutBufState = rob_idle;
>     > 26335-    69a0:    f880 5094     strb.w    r5, [r0, #148]    ; 0x94
>     > 26336-      (*tty->handler.write) (ctx, NULL, 0);
>     > 26337-    69a4:    f8d4 30c4     ldr.w    r3, [r4, #196]    ; 0xc4
>     > 26338-    69a8:    4670          mov    r0, lr
>     > 26339-    69aa:    4629          mov    r1, r5
>     > 26340-    69ac:    462a          mov    r2, r5
>     > 26341-    69ae:    4798          blx    r3
>     > 26342-      nToSend = 0;
>     > 26343-
>     > 26344-      /*
>     > 26345-       * check to see if snd wakeup callback was set
>     > 26346-       */
>     > --
>     > 26443-    6a12:    2600          movs    r6, #0
>     > 26444-    6a14:    e7ac          b.n    6970
>     > <rtems_termios_refill_transmitter+0x7c>
>     > 26445-      /*
>     > 26446-       * Buffer has become empty
>     > 26447-       */
>     > 26448:      tty->rawOutBufState = rob_idle;
>     > 26449-      (*tty->handler.write) (ctx, NULL, 0);
>     > 26450-      nToSend = 0;
>     > 26451-    6a16:    461d          mov    r5, r3
>     > 26452-    6a18:    e7aa          b.n    6970
>     > <rtems_termios_refill_transmitter+0x7c>
>     > 26453-    6a1a:    bf00          nop
>     > 26454-
>     > 26455-00006a1c <rtems_termios_txdaemon>:
>     > 26456-
>     > 26457-/*
>     > 26458- * this task actually processes any transmit events
>     > 26459- */
>     > 26460-static rtems_task rtems_termios_txdaemon(rtems_task_argument
>     argument)
>     > --
>     > 27083-      RTEMS_NO_PRIORITY,
>     > 27084-      &tty->rawOutBuf.Semaphore);
>     > 27085-    if (sc != RTEMS_SUCCESSFUL)
>     > 27086-    6cc0:    2800          cmp    r0, #0
>     > 27087-    6cc2:    f040 80d6     bne.w    6e72
>     > <rtems_termios_open_tty+0x2de>
>     > 27088:    tty->rawOutBufState = rob_idle;
>     > 27089-
>     > 27090-    /*
>     > 27091-     * Set callbacks
>     > 27092-     */
>     > 27093-    if (device_node != NULL) {
>     > 27094-    6cc6:    9b0e          ldr    r3, [sp, #56]    ; 0x38
>     > 27095-      RTEMS_SIMPLE_BINARY_SEMAPHORE | RTEMS_FIFO,
>     > 27096-      RTEMS_NO_PRIORITY,
>     > 27097-      &tty->rawOutBuf.Semaphore);
>     > 27098-    if (sc != RTEMS_SUCCESSFUL)
>     > 27099-      rtems_fatal_error_occurred (sc);
>     > 27100:    tty->rawOutBufState = rob_idle;
>     > 27101-    6cc8:    f884 0094     strb.w    r0, [r4, #148]    ; 0x94
>     > 27102-
>     > 27103-    /*
>     > 27104-     * Set callbacks
>     > 27105-     */
>     > 27106-    if (device_node != NULL) {
>     > 27107-    6ccc:    2b00          cmp    r3, #0
>     > 27108-    6cce:    f000 80e9     beq.w    6ea4
>     > <rtems_termios_open_tty+0x310>
>     > 27109-      device_node->tty = tty;
>     > 27110-      tty->handler = *device_node->handler;
>     > 27111-    6cd2:    f104 0cb8     add.w    ip, r4, #184    ; 0xb8
>     > 27112-    6cd6:    4666          mov    r6, ip
>     > --
>     > 29226-      /* disable interrupts    */
>     > 29227-      rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29228-      tty->flow_ctrl &= ~FL_OSTOP;
>     > 29229-    7442:    f8d4 30d8     ldr.w    r3, [r4, #216]    ; 0xd8
>     > 29230-      /* check for chars in output buffer (or rob_state?) */
>     > 29231:      if (tty->rawOutBufState != rob_idle) {
>     > 29232-    7446:    f894 2094     ldrb.w    r2, [r4, #148]    ; 0x94
>     > 29233-
>     > 29234-    /* has output been stopped due to received XOFF? */
>     > 29235-    if (tty->flow_ctrl & FL_OSTOP) {
>     > 29236-      /* disable interrupts    */
>     > 29237-      rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29238-      tty->flow_ctrl &= ~FL_OSTOP;
>     > 29239-    744a:    f023 0320     bic.w    r3, r3, #32
>     > 29240-    744e:    f8c4 30d8     str.w    r3, [r4, #216]    ; 0xd8
>     > 29241-      /* check for chars in output buffer (or rob_state?) */
>     > 29242:      if (tty->rawOutBufState != rob_idle) {
>     > 29243-    7452:    2a00          cmp    r2, #0
>     > 29244-    7454:    f040 80cf     bne.w    75f6
>     <rtems_termios_ioctl+0x306>
>     > 29245-    ARM_SWITCH_BACK
>     > 29246-    : ARM_SWITCH_OUTPUT
>     > 29247-    : [level] "r" (level)
>     > 29248-  );
>     > 29249-#elif defined(ARM_MULTILIB_ARCH_V7M)
>     > 29250-  __asm__ volatile (
>     > 29251-    7458:    f387 8811     msr    BASEPRI, r7
>     > 29252-      /* reenable interrupts */
>     > 29253-      rtems_termios_device_lock_release (ctx, &lock_context);
>     > 29254-    }
>     > --
>     > 29492-
>     > 29493-  rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29494-  tty->rawOutBuf.Tail = 0;
>     > 29495-    7572:    f8c4 0084     str.w    r0, [r4, #132]    ; 0x84
>     > 29496-  tty->rawOutBuf.Head = 0;
>     > 29497:  tty->rawOutBufState = rob_idle;
>     > 29498-    7576:    f884 0094     strb.w    r0, [r4, #148]    ; 0x94
>     > 29499-  rtems_termios_device_context *ctx = tty->device_context;
>     > 29500-  rtems_interrupt_lock_context lock_context;
>     > 29501-
>     > 29502-  rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29503-  tty->rawOutBuf.Tail = 0;
>     > 29504-  tty->rawOutBuf.Head = 0;
>     > 29505-    757a:    f8c4 0080     str.w    r0, [r4, #128]    ; 0x80
>     > 29506-    ARM_SWITCH_BACK
>     > 29507-    : ARM_SWITCH_OUTPUT
>     > 29508-    : [level] "r" (level)
>     > 29509-  );
>     > --
>     > 29562-
>     > 29563-  rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29564-  tty->rawOutBuf.Tail = 0;
>     > 29565-    75b0:    f8c4 0084     str.w    r0, [r4, #132]    ; 0x84
>     > 29566-  tty->rawOutBuf.Head = 0;
>     > 29567:  tty->rawOutBufState = rob_idle;
>     > 29568-    75b4:    f884 0094     strb.w    r0, [r4, #148]    ; 0x94
>     > 29569-  rtems_termios_device_context *ctx = tty->device_context;
>     > 29570-  rtems_interrupt_lock_context lock_context;
>     > 29571-
>     > 29572-  rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29573-  tty->rawOutBuf.Tail = 0;
>     > 29574-  tty->rawOutBuf.Head = 0;
>     > 29575-    75b8:    f8c4 0080     str.w    r0, [r4, #128]    ; 0x80
>     > 29576-    ARM_SWITCH_BACK
>     > 29577-    : ARM_SWITCH_OUTPUT
>     > 29578-    : [level] "r" (level)
>     > 29579-  );
>     > --
>     > 29629-    75f0:    2301          movs    r3, #1
>     > 29630-    75f2:    66e3          str    r3, [r4, #108]    ; 0x6c
>     > 29631-    75f4:    e77e          b.n    74f4
>     <rtems_termios_ioctl+0x204>
>     > 29632-      tty->flow_ctrl &= ~FL_OSTOP;
>     > 29633-      /* check for chars in output buffer (or rob_state?) */
>     > 29634:      if (tty->rawOutBufState != rob_idle) {
>     > 29635-        /* if chars available, call write function... */
>     > 29636-        (*tty->handler.write)(
>     > 29637-          ctx, &tty->rawOutBuf.theBuf[tty->rawOutBuf.Tail],1);
>     > 29638-    75f6:    f8d4 2084     ldr.w    r2, [r4, #132]    ; 0x84
>     > 29639-      rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 29640-      tty->flow_ctrl &= ~FL_OSTOP;
>     > 29641-      /* check for chars in output buffer (or rob_state?) */
>     > 29642:      if (tty->rawOutBufState != rob_idle) {
>     > 29643-        /* if chars available, call write function... */
>     > 29644-        (*tty->handler.write)(
>     > 29645-    75fa:    6fe1          ldr    r1, [r4, #124]    ; 0x7c
>     > 29646-    75fc:    f8d4 30c4     ldr.w    r3, [r4, #196]    ; 0xc4
>     > 29647-    7600:    4411          add    r1, r2
>     > 29648-    7602:    4628          mov    r0, r5
>     > 29649-    7604:    2201          movs    r2, #1
>     > 29650-    7606:    4798          blx    r3
>     > 29651-    7608:    e726          b.n    7458
>     <rtems_termios_ioctl+0x168>
>     > 29652-    760a:    bf00          nop
>     > 29653-
>     > 29654-0000760c <rtems_termios_puts>:
>     > --
>     > 29815-    76b2:    bf24          itt    cs
>     > 29816-    76b4:    f8d4 2088     ldrcs.w    r2, [r4, #136]    ; 0x88
>     > 29817-    76b8:    1a9b          subcs    r3, r3, r2
>     > 29818-    tty->rawOutBuf.Head = newHead;
>     > 29819-
>     > 29820:    if (tty->rawOutBufState == rob_idle) {
>     > 29821-    76ba:    f894 2094     ldrb.w    r2, [r4, #148]    ; 0x94
>     > 29822-    memcpy(&tty->rawOutBuf.theBuf[tty->rawOutBuf.Head], buf,
>     nToCopy);
>     > 29823-
>     > 29824-    newHead = tty->rawOutBuf.Head + nToCopy;
>     > 29825-    if (newHead >= tty->rawOutBuf.Size)
>     > 29826-      newHead -= tty->rawOutBuf.Size;
>     > 29827-    tty->rawOutBuf.Head = newHead;
>     > 29828-    76be:    f8c4 3080     str.w    r3, [r4, #128]    ; 0x80
>     > 29829-
>     > 29830:    if (tty->rawOutBufState == rob_idle) {
>     > 29831-    76c2:    b192          cbz    r2, 76ea
>     <rtems_termios_puts+0xde>
>     > 29832-    ARM_SWITCH_BACK
>     > 29833-    : ARM_SWITCH_OUTPUT
>     > 29834-    : [level] "r" (level)
>     > 29835-  );
>     > 29836-#elif defined(ARM_MULTILIB_ARCH_V7M)
>     > 29837-  __asm__ volatile (
>     > 29838-    76c4:    f385 8811     msr    BASEPRI, r5
>     > 29839-  if (tty->handler.mode == TERMIOS_POLLED) {
>     > 29840-    (*tty->handler.write)(ctx, buf, len);
>     > 29841-    return;
>     > 29842-  }
>     > --
>     > 29885-    76e8:    e7d2          b.n    7690 <rtems_termios_puts+0x84>
>     > 29886-    if (newHead >= tty->rawOutBuf.Size)
>     > 29887-      newHead -= tty->rawOutBuf.Size;
>     > 29888-    tty->rawOutBuf.Head = newHead;
>     > 29889-
>     > 29890:    if (tty->rawOutBufState == rob_idle) {
>     > 29891-      startXmit (tty, tty->rawOutBuf.Tail, false);
>     > 29892-    76ea:    f8d4 1084     ldr.w    r1, [r4, #132]    ; 0x84
>     > 29893-    76ee:    4620          mov    r0, r4
>     > 29894-    76f0:    f7ff f8ca     bl    6888 <startXmit>
>     > 29895-    76f4:    e7e6          b.n    76c4 <rtems_termios_puts+0xb8>
>     > 29896-  rtems_termios_device_context *ctx = tty->device_context;
>     > 29897-  rtems_interrupt_lock_context lock_context;
>     > 29898-  rtems_status_code sc;
>     > 29899-
>     > 29900-  if (tty->handler.mode == TERMIOS_POLLED) {
>     > 29901-    (*tty->handler.write)(ctx, buf, len);
>     > 29902-    76f6:    f8d2 30c4     ldr.w    r3, [r2, #196]    ; 0xc4
>     > --
>     > 31283-    while ((tty->rawInBuf.Head != tty->rawInBuf.Tail) &&
>     > 31284-    7be4:    428a          cmp    r2, r1
>     > 31285-    7be6:    f04f 0501     mov.w    r5, #1
>     > 31286-    7bea:    d968          bls.n    7cbe
>     <rtems_termios_read+0x1a6>
>     > 31287-             ==                (FL_MDXON | FL_ISNTXOF))
>     > 31288:            && ((tty->rawOutBufState == rob_idle)
>     > 31289-          || (tty->flow_ctrl & FL_OSTOP))) {
>     > 31290-          /* XON should be sent now... */
>     > 31291-          (*tty->handler.write)(
>     > 31292-            tty->device_context, (void
>     > *)&(tty->termios.c_cc[VSTART]), 1);
>     > 31293-    7bec:    f104 0849     add.w    r8, r4, #73    ; 0x49
>     > 31294-    7bf0:    e012          b.n    7c18
>     <rtems_termios_read+0x100>
>     > 31295-
>     > 31296-      rtems_termios_device_lock_release (ctx, &lock_context);
>     > 31297-
>     > 31298-      /* continue processing new character */
>     > 31299-      if (tty->termios.c_lflag & ICANON) {
>     > 31300-        if (siproc (c, tty))
>     > --
>     > 31401-        if (((tty->flow_ctrl & (FL_MDXON | FL_ISNTXOF))
>     > 31402-    7c56:    f8d4 20d8     ldr.w    r2, [r4, #216]    ; 0xd8
>     > 31403-    7c5a:    4013          ands    r3, r2
>     > 31404-    7c5c:    4553          cmp    r3, sl
>     > 31405-    7c5e:    d01e          beq.n    7c9e
>     <rtems_termios_read+0x186>
>     > 31406:            && ((tty->rawOutBufState == rob_idle)
>     > 31407-          || (tty->flow_ctrl & FL_OSTOP))) {
>     > 31408-          /* XON should be sent now... */
>     > 31409-          (*tty->handler.write)(
>     > 31410-            tty->device_context, (void
>     > *)&(tty->termios.c_cc[VSTART]), 1);
>     > 31411-        } else if (tty->flow_ctrl & FL_MDRTS) {
>     > 31412-    7c60:    f8d4 30d8     ldr.w    r3, [r4, #216]    ; 0xd8
>     > 31413-    7c64:    05da          lsls    r2, r3, #23
>     > 31414-    7c66:    d50b          bpl.n    7c80
>     <rtems_termios_read+0x168>
>     > 31415-          tty->flow_ctrl &= ~FL_IRTSOFF;
>     > 31416-    7c68:    f8d4 30d8     ldr.w    r3, [r4, #216]    ; 0xd8
>     > 31417-          /* activate RTS line */
>     > 31418-          if (tty->flow.start_remote_tx != NULL) {
>     > --
>     > 31477-         < tty->lowwater) {
>     > 31478-        tty->flow_ctrl &= ~FL_IREQXOF;
>     > 31479-        /* if tx stopped and XON should be sent... */
>     > 31480-        if (((tty->flow_ctrl & (FL_MDXON | FL_ISNTXOF))
>     > 31481-             ==                (FL_MDXON | FL_ISNTXOF))
>     > 31482:            && ((tty->rawOutBufState == rob_idle)
>     > 31483-    7c9e:    f894 3094     ldrb.w    r3, [r4, #148]    ; 0x94
>     > 31484-    7ca2:    b11b          cbz    r3, 7cac
>     <rtems_termios_read+0x194>
>     > 31485-          || (tty->flow_ctrl & FL_OSTOP))) {
>     > 31486-    7ca4:    f8d4 30d8     ldr.w    r3, [r4, #216]    ; 0xd8
>     > 31487-    7ca8:    0699          lsls    r1, r3, #26
>     > 31488-    7caa:    d5d9          bpl.n    7c60
>     <rtems_termios_read+0x148>
>     > 31489-          /* XON should be sent now... */
>     > 31490-          (*tty->handler.write)(
>     > 31491-    7cac:    f8d4 30c4     ldr.w    r3, [r4, #196]    ; 0xc4
>     > 31492-    7cb0:    f8d4 010c     ldr.w    r0, [r4, #268]    ; 0x10c
>     > 31493-    7cb4:    4641          mov    r1, r8
>     > 31494-    7cb6:    2201          movs    r2, #1
>     > --
>     > 32101-        /* disable interrupts    */
>     > 32102-        rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 32103-        tty->flow_ctrl &= ~FL_OSTOP;
>     > 32104-    7f34:    f8d4 30d8     ldr.w    r3, [r4, #216]    ; 0xd8
>     > 32105-        /* check for chars in output buffer (or rob_state?) */
>     > 32106:        if (tty->rawOutBufState != rob_idle) {
>     > 32107-    7f38:    f894 2094     ldrb.w    r2, [r4, #148]    ; 0x94
>     > 32108-    if (flow_rcv) {
>     > 32109-      /* restart output according to FL_ORCVXOF flag */
>     > 32110-      if ((tty->flow_ctrl & (FL_ORCVXOF | FL_OSTOP)) ==
>     FL_OSTOP) {
>     > 32111-        /* disable interrupts    */
>     > 32112-        rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 32113-        tty->flow_ctrl &= ~FL_OSTOP;
>     > 32114-    7f3c:    f023 0320     bic.w    r3, r3, #32
>     > 32115-    7f40:    f8c4 30d8     str.w    r3, [r4, #216]    ; 0xd8
>     > 32116-        /* check for chars in output buffer (or rob_state?) */
>     > 32117:        if (tty->rawOutBufState != rob_idle) {
>     > 32118-    7f44:    b94a          cbnz    r2, 7f5a
>     > <rtems_termios_enqueue_raw_characters+0x1ca>
>     > 32119-    ARM_SWITCH_BACK
>     > 32120-    : ARM_SWITCH_OUTPUT
>     > 32121-    : [level] "r" (level)
>     > 32122-  );
>     > 32123-#elif defined(ARM_MULTILIB_ARCH_V7M)
>     > 32124-  __asm__ volatile (
>     > 32125-    7f46:    f386 8811     msr    BASEPRI, r6
>     > 32126-    7f4a:    2601          movs    r6, #1
>     > 32127-    7f4c:    e760          b.n    7e10
>     > <rtems_termios_enqueue_raw_characters+0x80>
>     > 32128-        if (( !tty->tty_rcvwakeup ) && ( tty->tty_rcv.sw_pfn !=
>     > NULL )) {
>     > 32129-          (*tty->tty_rcv.sw_pfn)(&tty->termios,
>     tty->tty_rcv.sw_arg);
>     > --
>     > 32136-    7f52:    9300          str    r3, [sp, #0]
>     > 32137-    7f54:    f38a 8811     msr    BASEPRI, sl
>     > 32138-    7f58:    e75a          b.n    7e10
>     > <rtems_termios_enqueue_raw_characters+0x80>
>     > 32139-        tty->flow_ctrl &= ~FL_OSTOP;
>     > 32140-        /* check for chars in output buffer (or rob_state?) */
>     > 32141:        if (tty->rawOutBufState != rob_idle) {
>     > 32142-          /* if chars available, call write function... */
>     > 32143-          (*tty->handler.write)(
>     > 32144-            ctx,
>     &tty->rawOutBuf.theBuf[tty->rawOutBuf.Tail], 1);
>     > 32145-    7f5a:    f8d4 2084     ldr.w    r2, [r4, #132]    ; 0x84
>     > 32146-        rtems_termios_device_lock_acquire (ctx, &lock_context);
>     > 32147-        tty->flow_ctrl &= ~FL_OSTOP;
>     > 32148-        /* check for chars in output buffer (or rob_state?) */
>     > 32149:        if (tty->rawOutBufState != rob_idle) {
>     > 32150-          /* if chars available, call write function... */
>     > 32151-          (*tty->handler.write)(
>     > 32152-    7f5e:    6fe1          ldr    r1, [r4, #124]    ; 0x7c
>     > 32153-    7f60:    f8d4 30c4     ldr.w    r3, [r4, #196]    ; 0xc4
>     > 32154-    7f64:    4411          add    r1, r2
>     > 32155-    7f66:    4658          mov    r0, fp
>     > 32156-    7f68:    2201          movs    r2, #1
>     > 32157-    7f6a:    f8cd c004     str.w    ip, [sp, #4]
>     > 32158-    7f6e:    4798          blx    r3
>     > 32159-    7f70:    f8dd c004     ldr.w    ip, [sp, #4]
>     > 32160-    7f74:    e7e7          b.n    7f46
>     > <rtems_termios_enqueue_raw_characters+0x1b6>
>     > 32161-          + tty->rawInBuf.Size) % tty->rawInBuf.Size) >
>     > tty->highwater)) {
>     > --
>     > 32167-    7f76:    0692          lsls    r2, r2, #26
>     > 32168-    7f78:    d403          bmi.n    7f82
>     > <rtems_termios_enqueue_raw_characters+0x1f2>
>     > 32169-    7f7a:    f894 2094     ldrb.w    r2, [r4, #148]    ; 0x94
>     > 32170-    7f7e:    2a00          cmp    r2, #0
>     > 32171-    7f80:    d18c          bne.n    7e9c
>     > <rtems_termios_enqueue_raw_characters+0x10c>
>     > 32172:              (tty->rawOutBufState == rob_idle)) {
>     > 32173-            /* if tx is stopped due to XOFF or out of data */
>     > 32174-            /*    call write function here                 */
>     > 32175-            tty->flow_ctrl |= FL_ISNTXOF;
>     > 32176-    7f82:    f8d4 20d8     ldr.w    r2, [r4, #216]    ; 0xd8
>     > 32177-    7f86:    9301          str    r3, [sp, #4]
>     > 32178-    7f88:    f042 0202     orr.w    r2, r2, #2
>     > 32179-    7f8c:    f8c4 20d8     str.w    r2, [r4, #216]    ; 0xd8
>     > 32180-            (*tty->handler.write)(ctx,
>     > 32181-    7f90:    f8d4 30c4     ldr.w    r3, [r4, #196]    ; 0xc4
>     > 32182-    7f94:    4658          mov    r0, fp
>     > 32183-    7f96:    f104 014a     add.w    r1, r4, #74    ; 0x4a
>     > 32184-    7f9a:    2201          movs    r2, #1
>     > --
>     > 38521-    9512:    f000 f825     bl    9560
>     > <_Extension_Manager_initialization>
>     > 38522-
>     > 38523-  _POSIX_API_Initialize();
>     > 38524-    9516:    f000 f863     bl    95e0 <_POSIX_API_Initialize>
>     > 38525-    951a:    7025          strb    r5, [r4, #0]
>     > 38526:  _Thread_Create_idle();
>     > 38527-
>     > 38528-  /*
>     > 38529-   *  Scheduling can properly occur now as long as we avoid
>     > dispatching.
>     > 38530-   */
>     > 38531-}
>     > 38532-    951c:    e8bd 4038     ldmia.w    sp!, {r3, r4, r5, lr}
>     > 38533-   *  _Thread_Executing and _Thread_Heir are not set.
>     > 38534-   *
>     > 38535-   *  At this point all API extensions are in place.  After the
>     > call to
>     > 38536:   *  _Thread_Create_idle() _Thread_Executing and _Thread_Heir
>     > will be set.
>     > 38537-   */
>     > 38538:  _Thread_Create_idle();
>     > 38539:    9520:    f002 ba3a     b.w    b998 <_Thread_Create_idle>
>     > 38540-    9524:    20004618     .word    0x20004618
>     > 38541-    9528:    20004640     .word    0x20004640
>     > 38542-    952c:    200041d0     .word    0x200041d0
>     > 38543-    9530:    200041e0     .word    0x200041e0
>     > 38544-    9534:    2000429c     .word    0x2000429c
>     > 38545-    9538:    20004298     .word    0x20004298
>     > 38546-
>     > 38547-0000953c <rtems_initialize_before_drivers>:
>     > 38548-   *  Scheduling can properly occur now as long as we avoid
>     > dispatching.
>     > 38549-   */
>     > 38550-}
>     > 38551-
>     > --
>     > 48137-)
>     > 48138-{
>     > 48139-    b3c4:    4770          bx    lr
>     > 48140-    b3c6:    bf00          nop
>     > 48141-
>     > 48142:0000b3c8 <_Scheduler_default_Start_idle>:
>     > 48143-#if defined(RTEMS_SMP)
>     > 48144-  Thread_Control *needs_help;
>     > 48145-
>     > 48146-  needs_help =
>     > 48147-#endif
>     > 48148-  ( *scheduler->Operations.unblock )( scheduler, the_thread );
>     > 48149:    b3c8:    4801          ldr    r0, [pc, #4]    ; (b3d0
>     > <_Scheduler_default_Start_idle+0x8>)
>     > 48150-    b3ca:    6943          ldr    r3, [r0, #20]
>     > 48151-    b3cc:    4718          bx    r3
>     > 48152-    b3ce:    bf00          nop
>     > 48153-    b3d0:    0001847c     .word    0x0001847c
>     > 48154-
>     > 48155-0000b3d4 <_Scheduler_default_Tick>:
>     > 48156-  /*
>     > 48157-   *  If the thread is not preemptible or is not ready, then
>     > 48158-   *  just return.
>     > 48159-   */
>     > 48160-
>     > 48161-  if ( !executing->is_preemptible )
>     > --
>     > 49735-    b988:    0001847c     .word    0x0001847c
>     > 49736-    b98c:    0001d828     .word    0x0001d828
>     > 49737-    b990:    0001d814     .word    0x0001d814
>     > 49738-    b994:    0001d878     .word    0x0001d878
>     > 49739-
>     > 49740:0000b998 <_Thread_Create_idle>:
>     > 49741-    cpu
>     > 49742-  );
>     > 49743-}
>     > 49744-
>     > 49745:void _Thread_Create_idle( void )
>     > 49746-{
>     > 49747-    b998:    b5f0          push    {r4, r5, r6, r7, lr}
>     > 49748-  return maximum_internal_threads;
>     > 49749-}
>     > 49750-
>     > 49751-RTEMS_INLINE_ROUTINE Thread_Control
>     *_Thread_Internal_allocate( void )
>     > 49752-{
>     > 49753-  return (Thread_Control *)
>     > 49754:    b99a:    4f17          ldr    r7, [pc, #92]    ; (b9f8
>     > <_Thread_Create_idle+0x60>)
>     > 49755-    b99c:    b089          sub    sp, #36    ; 0x24
>     > 49756-    b99e:    4638          mov    r0, r7
>     > 49757-    b9a0:    f7fe ff74     bl    a88c
>     <_Objects_Allocate_unprotected>
>     > 49758-  _Thread_Initialize(
>     > 49759-    &_Thread_Internal_information,
>     > 49760:    idle,
>     > 49761-    _Scheduler_Get_by_CPU( cpu ),
>     > 49762-    NULL,        /* allocate the stack */
>     > 49763:    _Stack_Ensure_minimum(
>     > rtems_configuration_get_idle_task_stack_size() ),
>     > 49764:    b9a4:    4e15          ldr    r6, [pc, #84]    ; (b9fc
>     > <_Thread_Create_idle+0x64>)
>     > 49765- *
>     > 49766- * @return This method returns the minimum stack size;
>     > 49767- */
>     > 49768-RTEMS_INLINE_ROUTINE uint32_t _Stack_Minimum (void)
>     > 49769-{
>     > 49770-  return rtems_minimum_stack_size;
>     > 49771:    b9a6:    4a16          ldr    r2, [pc, #88]    ; (ba00
>     > <_Thread_Create_idle+0x68>)
>     > 49772-    b9a8:    6a73          ldr    r3, [r6, #36]    ; 0x24
>     > 49773-    b9aa:    6811          ldr    r1, [r2, #0]
>     > 49774-    b9ac:    4605          mov    r5, r0
>     > 49775-    b9ae:    428b          cmp    r3, r1
>     > 49776-    b9b0:    bf38          it    cc
>     > 49777-    b9b2:    460b          movcc    r3, r1
>     > 49778-   *  fields not explicitly assigned were explicitly zeroed by
>     > 49779-   *  _Workspace_Initialization.
>     > 49780-   */
>     > 49781:  idle = _Thread_Internal_allocate();
>     > 49782-
>     > 49783-  _Thread_Initialize(
>     > 49784:    b9b4:    4a13          ldr    r2, [pc, #76]    ; (ba04
>     > <_Thread_Create_idle+0x6c>)
>     > 49785:static void _Thread_Create_idle_for_cpu( Per_CPU_Control *cpu )
>     > 49786-{
>     > 49787-  Objects_Name    name;
>     > 49788:  Thread_Control *idle;
>     > 49789-
>     > 49790-  name.name_u32 = _Objects_Build_name( 'I', 'D', 'L', 'E' );
>     > 49791:    b9b6:    f8df e058     ldr.w    lr, [pc, #88]    ; ba10
>     > <_Thread_Create_idle+0x78>
>     > 49792-   *  fields not explicitly assigned were explicitly zeroed by
>     > 49793-   *  _Workspace_Initialization.
>     > 49794-   */
>     > 49795:  idle = _Thread_Internal_allocate();
>     > 49796-
>     > 49797-  _Thread_Initialize(
>     > 49798-    b9ba:    7811          ldrb    r1, [r2, #0]
>     > 49799-    b9bc:    2400          movs    r4, #0
>     > 49800-    b9be:    2201          movs    r2, #1
>     > 49801-    b9c0:    9300          str    r3, [sp, #0]
>     > 49802-    b9c2:    9102          str    r1, [sp, #8]
>     > 49803-    b9c4:    f8cd e01c     str.w    lr, [sp, #28]
>     > 49804-    b9c8:    4629          mov    r1, r5
>     > 49805-    b9ca:    4623          mov    r3, r4
>     > 49806-    b9cc:    9203          str    r2, [sp, #12]
>     > 49807-    b9ce:    4638          mov    r0, r7
>     > 49808-    b9d0:    9401          str    r4, [sp, #4]
>     > 49809-    b9d2:    9404          str    r4, [sp, #16]
>     > 49810-    b9d4:    9405          str    r4, [sp, #20]
>     > 49811-    b9d6:    9406          str    r4, [sp, #24]
>     > 49812:    b9d8:    4a0b          ldr    r2, [pc, #44]    ; (ba08
>     > <_Thread_Create_idle+0x70>)
>     > 49813-    b9da:    f000 f96d     bl    bcb8 <_Thread_Initialize>
>     > 49814-   *             MUST be done before _Thread_Start is invoked.
>     > 49815-   */
>     > 49816-  cpu->heir      =
>     > 49817:  cpu->executing = idle;
>     > 49818-
>     > 49819-  _Thread_Start(
>     > 49820-    b9de:    6a32          ldr    r2, [r6, #32]
>     > 49821-  /*
>     > 49822-   *  WARNING!!! This is necessary to "kick" start the
>     system and
>     > 49823-   *             MUST be done before _Thread_Start is invoked.
>     > 49824-   */
>     > 49825-  cpu->heir      =
>     > 49826:  cpu->executing = idle;
>     > 49827:    b9e0:    4e0a          ldr    r6, [pc, #40]    ; (ba0c
>     > <_Thread_Create_idle+0x74>)
>     > 49828-
>     > 49829-  _Thread_Start(
>     > 49830-    b9e2:    9400          str    r4, [sp, #0]
>     > 49831-    b9e4:    9601          str    r6, [sp, #4]
>     > 49832-    b9e6:    4628          mov    r0, r5
>     > 49833-    b9e8:    4621          mov    r1, r4
>     > 49834-    b9ea:    4623          mov    r3, r4
>     > 49835-  /*
>     > 49836-   *  WARNING!!! This is necessary to "kick" start the
>     system and
>     > 49837-   *             MUST be done before _Thread_Start is invoked.
>     > 49838-   */
>     > 49839-  cpu->heir      =
>     > 49840:  cpu->executing = idle;
>     > 49841-    b9ec:    60b5          str    r5, [r6, #8]
>     > 49842-
>     > 49843-  /*
>     > 49844-   *  WARNING!!! This is necessary to "kick" start the
>     system and
>     > 49845-   *             MUST be done before _Thread_Start is invoked.
>     > 49846-   */
>     > 49847-  cpu->heir      =
>     > 49848-    b9ee:    60f5          str    r5, [r6, #12]
>     > 49849:  cpu->executing = idle;
>     > 49850-
>     > 49851-  _Thread_Start(
>     > 49852-    b9f0:    f000 fee0     bl    c7b4 <_Thread_Start>
>     > 49853-
>     > 49854-    if ( _Per_CPU_Is_processor_started( cpu ) ) {
>     > 49855:      _Thread_Create_idle_for_cpu( cpu );
>     > 49856-    }
>     > 49857-  }
>     > 49858-}
>     > 49859-    b9f4:    b009          add    sp, #36    ; 0x24
>     > 49860-    b9f6:    bdf0          pop    {r4, r5, r6, r7, pc}
>     > 49861-    b9f8:    200042c0     .word    0x200042c0
>     > 49862-    b9fc:    000183c0     .word    0x000183c0
>     > 49863-    ba00:    200011c0     .word    0x200011c0
>     > 49864-    ba04:    200011bc     .word    0x200011bc
>     > 49865-    ba08:    0001847c     .word    0x0001847c
>     > 49866-    ba0c:    20004640     .word    0x20004640
>     > 49867-    ba10:    49444c45     .word    0x49444c45
>     > --
>     > 54093-  const Scheduler_Control *scheduler,
>     > 54094-  Thread_Control          *the_thread,
>     > 54095-  Per_CPU_Control         *cpu
>     > 54096-)
>     > 54097-{
>     > 54098:  ( *scheduler->Operations.start_idle )( scheduler,
>     the_thread, cpu );
>     > 54099-    c7de:    4809          ldr    r0, [pc, #36]    ; (c804
>     > <_Thread_Start+0x50>)
>     > 54100-      _Thread_Ready( the_thread );
>     > 54101-    } else {
>     > 54102-      const Scheduler_Control *scheduler =
>     _Scheduler_Get_by_CPU(
>     > cpu );
>     > 54103-
>     > 54104-      if ( scheduler != NULL ) {
>     > 54105-        the_thread->current_state = STATES_READY;
>     > 54106-    c7e0:    2200          movs    r2, #0
>     > 54107-    c7e2:    612a          str    r2, [r5, #16]
>     > 54108-    c7e4:    6b43          ldr    r3, [r0, #52]    ; 0x34
>     > 54109-    c7e6:    4629          mov    r1, r5
>     > 54110-    c7e8:    9a05          ldr    r2, [sp, #20]
>     >
>     > On Wed, Apr 24, 2019 at 2:59 PM Christian Mauderer
>     > <christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     > <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>> wrote:
>     >
>     >     Am 24.04.19 um 02:35 schrieb Jython:
>     >     > yes, I need to do low power for stm32f4
>     >     > will this line work __asm__ volatile ("wfi");?
>     >
>     >     That line should be correct. Please note that the instruction
>     is already
>     >     used in the armv7 idle thread:
>     >
>     >   
>      https://git.rtems.org/rtems/tree/cpukit/score/cpu/arm/armv7-thread-idle.c#n32
>     >
>     >     The stm32f4 is a Cortex-M4 so it's quite likely that this
>     routine is
>     >     used. You can check by doing an "arm-rtems5-objdump -dS" on
>     your file
>     >     and search for the idle body.
>     >
>     >     With kind regards
>     >
>     >     Christian
>     >
>     >     >
>     >     >
>     >     > On Tue, Apr 23, 2019 at 10:28 PM Christian Mauderer
>     >     > <christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>
>     >     > <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>>> wrote:
>     >     >
>     >     >     Am 22.04.19 um 09:47 schrieb Jython:
>     >     >     > HI, ALL!
>     >     >     > wfi
>     >     >   
>     >   
>       http://www.keil.com/support/man/docs/armcc/armcc_chr1359125004400.htm
>     >     >     > how can i call the arm __wfi?
>     >     >     >
>     >     >     > _______________________________________________
>     >     >     > users mailing list
>     >     >     > users at rtems.org <mailto:users at rtems.org>
>     <mailto:users at rtems.org <mailto:users at rtems.org>>
>     >     <mailto:users at rtems.org <mailto:users at rtems.org>
>     <mailto:users at rtems.org <mailto:users at rtems.org>>>
>     >     >     > http://lists.rtems.org/mailman/listinfo/users
>     >     >     >
>     >     >
>     >     >     Hello Jython,
>     >     >
>     >     >     WFI is an assembler instruction. The Keil wrapper isn't
>     >     available in
>     >     >     gcc. I know of no direct replacement. Most likely you need a
>     >     gcc inline
>     >     >     assembly for that.
>     >     >
>     >     >     May I ask why you would need "wfi"? If you use a operating
>     >     system, the
>     >     >     system typically handles such low level stuff for you.
>     The only
>     >     >     application that springs to mind for that instruction is
>     >     overwriting the
>     >     >     idle loop to save energy.
>     >     >
>     >     >     Best regards
>     >     >
>     >     >     Christian
>     >     >
>     >     >     --
>     >     >     --------------------------------------------
>     >     >     embedded brains GmbH
>     >     >     Herr Christian Mauderer
>     >     >     Dornierstr. 4
>     >     >     D-82178 Puchheim
>     >     >     Germany
>     >     >     email: christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>
>     >     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>>
>     >     >     Phone: +49-89-18 94 741 - 18
>     >     >     Fax:   +49-89-18 94 741 - 08
>     >     >     PGP: Public key available on request.
>     >     >
>     >     >     Diese Nachricht ist keine geschäftliche Mitteilung im Sinne
>     >     des EHUG.
>     >     >
>     >
>     >     --
>     >     --------------------------------------------
>     >     embedded brains GmbH
>     >     Herr Christian Mauderer
>     >     Dornierstr. 4
>     >     D-82178 Puchheim
>     >     Germany
>     >     email: christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     >     <mailto:christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>>
>     >     Phone: +49-89-18 94 741 - 18
>     >     Fax:   +49-89-18 94 741 - 08
>     >     PGP: Public key available on request.
>     >
>     >     Diese Nachricht ist keine geschäftliche Mitteilung im Sinne
>     des EHUG.
>     >
> 
>     -- 
>     --------------------------------------------
>     embedded brains GmbH
>     Herr Christian Mauderer
>     Dornierstr. 4
>     D-82178 Puchheim
>     Germany
>     email: christian.mauderer at embedded-brains.de
>     <mailto:christian.mauderer at embedded-brains.de>
>     Phone: +49-89-18 94 741 - 18
>     Fax:   +49-89-18 94 741 - 08
>     PGP: Public key available on request.
> 
>     Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
> 

-- 
--------------------------------------------
embedded brains GmbH
Herr Christian Mauderer
Dornierstr. 4
D-82178 Puchheim
Germany
email: christian.mauderer at embedded-brains.de
Phone: +49-89-18 94 741 - 18
Fax:   +49-89-18 94 741 - 08
PGP: Public key available on request.

Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.



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