[PATCH] Beaglebone: Fix the IRQ handling code

Ben Gras beng at shrike-systems.com
Sat Feb 27 21:16:12 UTC 2016


I'm doing a rebase & build right now, thanks for the reminder.

On Fri, Feb 26, 2016 at 10:32 PM, Martin Galvan
<martin.galvan at tallertechnologies.com> wrote:
> Hi Ben! Sorry to bother, were you able to test my changes to the BBB
> interrupt handler?
>
> On Fri, Feb 12, 2016 at 11:09 AM, Martin Galvan
> <martin.galvan at tallertechnologies.com> wrote:
>> Thanks Ben! Indeed, any further testing is more than welcome :)
>>
>> On Thu, Feb 11, 2016 at 7:55 PM, Ben Gras <beng at shrike-systems.com> wrote:
>>> This looks like great work. Please let me test it (I'll try the GPIO
>>> interrupt trigger) & I'll merge it as soon as I have time.
>>>
>>> Thank you!
>>>
>>> Cheers,
>>> Ben
>>>
>>>
>>> On Thu, Feb 11, 2016 at 3:27 PM, Martin Galvan
>>> <martin.galvan at tallertechnologies.com> wrote:
>>>> This patch makes the following changes to the Beaglebone IRQ handling code:
>>>>
>>>> - Disable support for nested interrupts.
>>>> - Detect spurious IRQs using the SPURIOUSIRQ field of the INTC_SIR_IRQ register.
>>>> - Acknowledge spurious IRQs by setting the NewIRQAgr bit of the INTC_CONTROL
>>>>   register. This cleans the SPURIOUSIRQ field and allows new interrupts
>>>>   to be generated.
>>>> - Improve the get_mir_reg function a bit.
>>>>
>>>> The Beaglebone bsp_interrupt_dispach function has been troublesome for a while now.
>>>> We've seen it break the GPIO API (https://lists.rtems.org/pipermail/devel/2015-November/012995.html),
>>>> the RTEMS interrupt server (https://lists.rtems.org/pipermail/devel/2015-July/011865.html),
>>>> and now we've been getting spurious interrupts when trying to use the I2C module.
>>>>
>>>> We've done a lot of testing and concluded that the cause of most of these issues
>>>> is the way nested interrupts are being handled. The AM335X manual states that
>>>> the interrupt handling sequence should be as follows:
>>>>
>>>> 1. Identify the IRQ source by reading the ActiveIRQ field of the INTC_SIR_IRQ
>>>>    register.
>>>> 2. Jump to the corresponding IRQ handler, which should serve the IRQ and
>>>>    deassert the interrupt condition at the peripheral side.
>>>> 3. Enable the processing of new IRQs at the Interrupt Controller side by setting
>>>>    the NewIRQAgr bit of the INTC_CONTROL register.
>>>> 4. Finally, enable IRQs at the CPU side. This is done later in
>>>>    _ARMV4_Exception_interrupt.
>>>>
>>>> Right now the Beaglebone bsp_interrupt_dispach enables IRQs at the INTC and CPU
>>>> before jumping to the interrupt handler to allow for nested IRQs.
>>>> Before doing so, it calls bsp_interrupt_disable to mask the IRQ source and avoid
>>>> having it constantly fire new IRQs. After it's done it re-enables the IRQ
>>>> by calling bsp_interrupt_enable. These calls break the GPIO API and the
>>>> RTEMS interrupt server machinery, and we suspect it's also causing the spurious
>>>> interrupts we saw with the I2C module.
>>>>
>>>> The correct way to enable interrupt nesting according to both the manual and
>>>> the AM335X StarterWare code is to allow only interrupts of a higher priority
>>>> to preempt the current one. This can be achieved by setting the INTC_THRESHOLD
>>>> register to the priority of the current IRQ. However, in our case this isn't
>>>> necessary since all the interrupt priorities are set to 0 (the highest possible)
>>>> in bsp_interrupt_facility_initialize. We may implement this in a future patch,
>>>> if required.
>>>>
>>>> We've tested this quite extensively on a number of different applications, and
>>>> it's working fine.
>>>>
>>>> Closes #2580.
>>>> ---
>>>>  c/src/lib/libbsp/arm/beagle/irq.c           | 82 +++++++++++++++--------------
>>>>  c/src/lib/libcpu/arm/shared/include/omap3.h |  3 +-
>>>>  2 files changed, 44 insertions(+), 41 deletions(-)
>>>>
>>>> diff --git a/c/src/lib/libbsp/arm/beagle/irq.c b/c/src/lib/libbsp/arm/beagle/irq.c
>>>> index c6485cd..d080a5e 100644
>>>> --- a/c/src/lib/libbsp/arm/beagle/irq.c
>>>> +++ b/c/src/lib/libbsp/arm/beagle/irq.c
>>>> @@ -18,6 +18,7 @@
>>>>  #include <bsp.h>
>>>>  #include <bsp/irq-generic.h>
>>>>  #include <bsp/linker-symbols.h>
>>>> +#include <bsp/fatal.h>
>>>>
>>>>  #include <rtems/score/armv4.h>
>>>>
>>>> @@ -43,77 +44,78 @@ static struct omap_intr omap_intr = {
>>>>  };
>>>>  #endif
>>>>
>>>> -static int irqs_enabled[BSP_INTERRUPT_VECTOR_MAX+1];
>>>> +/* Enables interrupts at the Interrupt Controller side. */
>>>> +static inline void omap_irq_ack(void)
>>>> +{
>>>> +  mmio_write(omap_intr.base + OMAP3_INTCPS_CONTROL, OMAP3_INTR_NEWIRQAGR);
>>>>
>>>> -volatile static int level = 0;
>>>> +  /* Flush data cache to make sure all the previous writes are done
>>>> +     before re-enabling interrupts. */
>>>> +  flush_data_cache();
>>>> +}
>>>>
>>>>  void bsp_interrupt_dispatch(void)
>>>>  {
>>>> -  /* get irq */
>>>> -  uint32_t reg = mmio_read(omap_intr.base + OMAP3_INTCPS_SIR_IRQ);
>>>> -  int irq;
>>>> -  irq = reg & OMAP3_INTR_ACTIVEIRQ_MASK;
>>>> +  const uint32_t reg = mmio_read(omap_intr.base + OMAP3_INTCPS_SIR_IRQ);
>>>>
>>>> -  if(!irqs_enabled[irq]) {
>>>> -       /* Ignore spurious interrupt */
>>>> -  } else {
>>>> -    bsp_interrupt_vector_disable(irq);
>>>> -
>>>> -    /* enable new interrupts, and flush data cache to make sure
>>>> -     * it hits the intc
>>>> -     */
>>>> -    mmio_write(omap_intr.base + OMAP3_INTCPS_CONTROL, OMAP3_INTR_NEWIRQAGR);
>>>> -    flush_data_cache();
>>>> -    mmio_read(omap_intr.base + OMAP3_INTCPS_SIR_IRQ);
>>>> -    flush_data_cache();
>>>> -
>>>> -    /* keep current irq masked but enable unmasked ones */
>>>> -    uint32_t psr = _ARMV4_Status_irq_enable();
>>>> -    bsp_interrupt_handler_dispatch(irq);
>>>> -
>>>> -    _ARMV4_Status_restore(psr);
>>>> +  if ((reg & OMAP3_INTR_SPURIOUSIRQ_MASK) != OMAP3_INTR_SPURIOUSIRQ_MASK) {
>>>> +    const rtems_vector_number irq = reg & OMAP3_INTR_ACTIVEIRQ_MASK;
>>>>
>>>> -    bsp_interrupt_vector_enable(irq);
>>>> +    bsp_interrupt_handler_dispatch(irq);
>>>> +  } else {
>>>> +    /* Ignore spurious interrupts. We'll still ACK it so new interrupts
>>>> +       can be generated. */
>>>>    }
>>>> +
>>>> +  omap_irq_ack();
>>>>  }
>>>>
>>>> -static uint32_t get_mir_reg(int vector, uint32_t *mask)
>>>> +/* There are 4 32-bit interrupt mask registers for a total of 128 interrupts.
>>>> +   The IRQ number tells us which register to use. */
>>>> +static uint32_t omap_get_mir_reg(rtems_vector_number vector, uint32_t *const mask)
>>>>  {
>>>> -  *mask = 1UL << (vector % 32);
>>>> -
>>>> -  if(vector <   0) while(1) ;
>>>> -  if(vector <  32) return OMAP3_INTCPS_MIR0;
>>>> -  if(vector <  64) return OMAP3_INTCPS_MIR1;
>>>> -  if(vector <  96) return OMAP3_INTCPS_MIR2;
>>>> -  if(vector < 128) return OMAP3_INTCPS_MIR3;
>>>> -  while(1) ;
>>>> +  uint32_t mir_reg;
>>>> +
>>>> +  /* Select which bit to set/clear in the MIR register. */
>>>> +  *mask = 1ul << (vector % 32u);
>>>> +
>>>> +  if (vector < 32u) {
>>>> +    mir_reg = OMAP3_INTCPS_MIR0;
>>>> +  } else if (vector < 64u) {
>>>> +    mir_reg = OMAP3_INTCPS_MIR1;
>>>> +  } else if (vector < 96u) {
>>>> +    mir_reg = OMAP3_INTCPS_MIR2;
>>>> +  } else if (vector < 128u) {
>>>> +    mir_reg = OMAP3_INTCPS_MIR3;
>>>> +  } else {
>>>> +    /* Invalid IRQ number. This should never happen. */
>>>> +    bsp_fatal(0);
>>>> +  }
>>>> +
>>>> +  return mir_reg;
>>>>  }
>>>>
>>>>  rtems_status_code bsp_interrupt_vector_enable(rtems_vector_number vector)
>>>>  {
>>>>    uint32_t mask, cur;
>>>> -  uint32_t mir_reg = get_mir_reg(vector, &mask);
>>>> +  uint32_t mir_reg = omap_get_mir_reg(vector, &mask);
>>>>
>>>>    cur = mmio_read(omap_intr.base + mir_reg);
>>>>    mmio_write(omap_intr.base + mir_reg, cur & ~mask);
>>>>    flush_data_cache();
>>>>
>>>> -  irqs_enabled[vector] = 1;
>>>> -
>>>>    return RTEMS_SUCCESSFUL;
>>>>  }
>>>>
>>>>  rtems_status_code bsp_interrupt_vector_disable(rtems_vector_number vector)
>>>>  {
>>>>    uint32_t mask, cur;
>>>> -  uint32_t mir_reg = get_mir_reg(vector, &mask);
>>>> +  uint32_t mir_reg = omap_get_mir_reg(vector, &mask);
>>>>
>>>>    cur = mmio_read(omap_intr.base + mir_reg);
>>>>    mmio_write(omap_intr.base + mir_reg, cur | mask);
>>>>    flush_data_cache();
>>>>
>>>> -  irqs_enabled[vector] = 0;
>>>> -
>>>>    return RTEMS_SUCCESSFUL;
>>>>  }
>>>>
>>>> diff --git a/c/src/lib/libcpu/arm/shared/include/omap3.h b/c/src/lib/libcpu/arm/shared/include/omap3.h
>>>> index f28e5e5..0cc43d6 100644
>>>> --- a/c/src/lib/libcpu/arm/shared/include/omap3.h
>>>> +++ b/c/src/lib/libcpu/arm/shared/include/omap3.h
>>>> @@ -72,7 +72,8 @@
>>>>  #define OMAP3_INTR_ILR(base,m) \
>>>>      (base + OMAP3_INTCPS_ILR0 + 0x4 * (m))
>>>>
>>>> -#define OMAP3_INTR_ACTIVEIRQ_MASK 0x7f /* Active IRQ mask for SIR_IRQ */
>>>> +#define OMAP3_INTR_SPURIOUSIRQ_MASK (0x1FFFFFF << 7) /* Spurious IRQ mask for SIR_IRQ */
>>>> +#define OMAP3_INTR_ACTIVEIRQ_MASK 0x7F /* Active IRQ mask for SIR_IRQ */
>>>>  #define OMAP3_INTR_NEWIRQAGR      0x1  /* New IRQ Generation */
>>>>
>>>>  #define OMAP3_DM337X_NR_IRQ_VECTORS    96
>>>> --
>>>> 2.7.1
>>>>
>>
>>
>>
>> --
>>
>>
>> Martin Galvan
>>
>> Software Engineer
>>
>> Taller Technologies Argentina
>>
>>
>> San Lorenzo 47, 3rd Floor, Office 5
>>
>> Córdoba, Argentina
>>
>> Phone: 54 351 4217888 / +54 351 4218211
>
>
>
> --
>
>
> Martin Galvan
>
> Software Engineer
>
> Taller Technologies Argentina
>
>
> San Lorenzo 47, 3rd Floor, Office 5
>
> Córdoba, Argentina
>
> Phone: 54 351 4217888 / +54 351 4218211


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