[PATCH] bsps/i386: Separate variable for i8259 IRQs disable due to in progress state.
Chris Johns
chrisj at rtems.org
Sun Sep 25 01:24:06 UTC 2016
Hi Pavel,
Thank you for this. What testing has the patch had?
It needs to be tested on real hardware and hardware which showed the
spurious interrupt issue. The issue appears around the interrupt enable
call and my guess is it relates to some type of a race condition in the
PIC between the signals and some piece of register timing. I timed the
spurious interrupt always appearing usecs after the enable.
I am currently unable to test this patch and I am not sure when I can. I
will do my best next week.
On 25/09/2016 10:48, Pavel Pisa wrote:
> From: Pavel Pisa <pisa at cmp.felk.cvut.cz>
>
> The global state of enabled and disabled interrupts has to hold
> interrupts really disabled by drivers and system. If the state is
> combined with interrupts temporarily disabled because they are
> processed at given time then it is impossible to maintain state
> by interrupt handlers in drivers.
> ---
> c/src/lib/libbsp/i386/shared/irq/irq.c | 51 +++++++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 19 deletions(-)
>
> diff --git a/c/src/lib/libbsp/i386/shared/irq/irq.c b/c/src/lib/libbsp/i386/shared/irq/irq.c
> index 0511257..8316fe6 100644
> --- a/c/src/lib/libbsp/i386/shared/irq/irq.c
> +++ b/c/src/lib/libbsp/i386/shared/irq/irq.c
> @@ -51,7 +51,22 @@ static enum intr_trigger irq_trigger[BSP_IRQ_LINES_NUMBER];
> * while upper bits are interrupt on the slave PIC.
> * This cache is initialized in ldseg.s
> */
> -static rtems_i8259_masks i8259a_cache = 0xFFFB;
> +static rtems_i8259_masks i8259a_imr_cache = 0xFFFB;
> +static rtems_i8259_masks i8259a_in_progress = 0;
Should these be volatile to be sure?
> +
> +static inline
> +void BSP_i8259a_irq_update_master_imr( void )
> +{
> + rtems_i8259_masks mask = i8259a_in_progress | i8259a_imr_cache;
> + outport_byte( PIC_MASTER_IMR_IO_PORT, mask & 0xff );
> +}
> +
> +static inline
> +void BSP_i8259a_irq_update_slave_imr( void )
> +{
> + rtems_i8259_masks mask = i8259a_in_progress | i8259a_imr_cache;
> + outport_byte( PIC_SLAVE_IMR_IO_PORT, ( mask >> 8 ) & 0xff );
> +}
>
> /*
> * Print the stats.
> @@ -107,7 +122,7 @@ static inline uint8_t BSP_i8259a_irq_in_service_reg(uint32_t ioport)
> /*-------------------------------------------------------------------------+
> | Function: BSP_irq_disable_at_i8259a
> | Description: Mask IRQ line in appropriate PIC chip.
> -| Global Variables: i8259a_cache
> +| Global Variables: i8259a_imr_cache, i8259a_in_progress
> | Arguments: vector_offset - number of IRQ line to mask.
> | Returns: 0 is OK.
> +--------------------------------------------------------------------------*/
> @@ -119,15 +134,15 @@ static int BSP_irq_disable_at_i8259a(const rtems_irq_number irqLine)
> rtems_interrupt_disable(level);
>
> mask = 1 << irqLine;
> - i8259a_cache |= mask;
> + i8259a_imr_cache |= mask;
>
> if (irqLine < 8)
> {
> - outport_byte(PIC_MASTER_IMR_IO_PORT, i8259a_cache & 0xff);
> + BSP_i8259a_irq_update_master_imr();
> }
> else
> {
> - outport_byte(PIC_SLAVE_IMR_IO_PORT, (i8259a_cache >> 8) & 0xff);
> + BSP_i8259a_irq_update_slave_imr();
> }
>
> rtems_interrupt_enable(level);
> @@ -138,7 +153,7 @@ static int BSP_irq_disable_at_i8259a(const rtems_irq_number irqLine)
> /*-------------------------------------------------------------------------+
> | Function: BSP_irq_enable_at_i8259a
> | Description: Unmask IRQ line in appropriate PIC chip.
> -| Global Variables: i8259a_cache
> +| Global Variables: i8259a_imr_cache, i8259a_in_progress
> | Arguments: irqLine - number of IRQ line to mask.
> | Returns: Nothing.
> +--------------------------------------------------------------------------*/
> @@ -152,19 +167,19 @@ static int BSP_irq_enable_at_i8259a(const rtems_irq_number irqLine)
> rtems_interrupt_disable(level);
>
> mask = 1 << irqLine;
> - i8259a_cache &= ~mask;
> + i8259a_imr_cache &= ~mask;
>
> if (irqLine < 8)
> {
> isr = BSP_i8259a_irq_in_service_reg(PIC_MASTER_COMMAND_IO_PORT);
> irr = BSP_i8259a_irq_int_request_reg(PIC_MASTER_COMMAND_IO_PORT);
> - outport_byte(PIC_MASTER_IMR_IO_PORT, i8259a_cache & 0xff);
> + BSP_i8259a_irq_update_master_imr();
> }
> else
> {
> isr = BSP_i8259a_irq_in_service_reg(PIC_SLAVE_COMMAND_IO_PORT);
> irr = BSP_i8259a_irq_int_request_reg(PIC_SLAVE_COMMAND_IO_PORT);
> - outport_byte(PIC_SLAVE_IMR_IO_PORT, (i8259a_cache >> 8) & 0xff);
> + BSP_i8259a_irq_update_slave_imr();
> }
>
> if (((isr ^ irr) & mask) != 0)
> @@ -298,7 +313,7 @@ void BSP_dispatch_isr(int vector);
>
> void BSP_dispatch_isr(int vector)
> {
> - uint16_t old_imr = 0;
> + rtems_i8259_masks in_progress_save = 0;
>
> if (vector < BSP_IRQ_VECTOR_NUMBER) {
> /*
> @@ -329,10 +344,10 @@ void BSP_dispatch_isr(int vector)
> * vector clear.
> */
> if (vector <= BSP_IRQ_MAX_ON_i8259A) {
> - old_imr = i8259a_cache;
> - i8259a_cache |= irq_mask_or_tbl[vector];
> - outport_byte(PIC_MASTER_IMR_IO_PORT, i8259a_cache & 0xff);
> - outport_byte(PIC_SLAVE_IMR_IO_PORT, (i8259a_cache >> 8) & 0xff);
> + in_progress_save = i8259a_in_progress;
> + i8259a_in_progress |= irq_mask_or_tbl[vector];
> + BSP_i8259a_irq_update_master_imr();
> + BSP_i8259a_irq_update_slave_imr();
> }
>
> /*
> @@ -365,11 +380,9 @@ void BSP_dispatch_isr(int vector)
> * again.
> */
> if (vector <= BSP_IRQ_MAX_ON_i8259A) {
> - if (irq_trigger[vector] == INTR_TRIGGER_LEVEL)
> - old_imr |= 1 << vector;
Looking at the interrupt server I see a disable in the trigger call
which means it should be ok to remove this code. I am wondering if this
piece of code is an artefact of the comparison of the code in FreeBSD I
did which always uses an interrupt server and may assume the interrupt
is masked.
Chris
> - i8259a_cache = old_imr;
> - outport_byte(PIC_MASTER_IMR_IO_PORT, i8259a_cache & 0xff);
> - outport_byte(PIC_SLAVE_IMR_IO_PORT, (i8259a_cache >> 8) & 0xff);
> + i8259a_in_progress = in_progress_save;
> + BSP_i8259a_irq_update_master_imr();
> + BSP_i8259a_irq_update_slave_imr();
> }
> }
> }
>
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