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SubjectRe: [PATCH 2/2] iio: adc: stm32: Fix check for spurious IRQs on STM32F4
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On 5/7/22 00:56, Yannick Brosseau wrote:
> The check for spurious IRQs introduced in 695e2f5c289bb assumed that the bits
> in the control and status registers are aligned. This is true for the H7 and MP1
> version, but not the F4.
>
> Instead of comparing both registers bitwise, we check the bit in the status and control
> for each interrupt we are interested in.
>

Hi Yannick,

I propose a different approach, see here after.

Same as for patch one,
Fixes: 695e2f5c289b ("iio: adc: stm32-adc: fix a regression when using
dma and irq")

> Signed-off-by: Yannick Brosseau <yannick.brosseau@gmail.com>
> ---
> drivers/iio/adc/stm32-adc.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index a68ecbda6480..5b0f138333ee 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1422,9 +1422,10 @@ static irqreturn_t stm32_adc_threaded_isr(int irq, void *data)
> return IRQ_HANDLED;
> }
>
> - if (!(status & mask))
> + if(!((status & regs->isr_eoc.mask) && (mask & regs->ier_eoc.mask)) ||
> + ((status & regs->isr_ovr.mask) && (mask & regs->ier_ovr.mask)))
> dev_err_ratelimited(&indio_dev->dev,
> - "Unexpected IRQ: IER=0x%08x, ISR=0x%08x\n",
> + "Unexpected IRQ: CR1/IER=0x%08x, SR/ISR=0x%08x\n",
> mask, status);


Here, a slightly different approach could be used... There's a long
pending discussion, where Olivier or I should push further patches to
support threadirqs (hopefully soon).
In this discussion with Jonathan [1], he exposed the need to remove this
message. Words from Jonathan:
"This seems 'unusual'. If this is a spurious interrupt we should be
returning IRQ_NONE and letting the spurious interrupt protection
stuff kick in."

[1]
https://lore.kernel.org/linux-arm-kernel/20210116175333.4d8684c5@archlinux/

So basically, I suggest to completely get rid of this message:

- if (!(status & mask))
- dev_err_ratelimited(&indio_dev->dev,
- "Unexpected IRQ: IER=0x%08x, ISR=0x%08x\n",
- mask, status);

>
> return IRQ_NONE;
> @@ -1438,7 +1439,9 @@ static irqreturn_t stm32_adc_isr(int irq, void *data)
> u32 status = stm32_adc_readl(adc, regs->isr_eoc.reg);
> u32 mask = stm32_adc_readl(adc, regs->ier_eoc.reg);
>
> - if (!(status & mask))
> + /* Check that we have the interrupt we care about are enabled and active */
> + if(!((status & regs->isr_eoc.mask) && (mask & regs->ier_eoc.mask)) ||
> + ((status & regs->isr_ovr.mask) && (mask & regs->ier_ovr.mask)))
> return IRQ_WAKE_THREAD;

Here the statement becomes useless, so it could be removed:
- u32 mask = stm32_adc_readl(adc, regs->ier_eoc.reg);
-
- if (!(status & mask))
- return IRQ_WAKE_THREAD;

This would avoid some complexity here (and so headaches or regressions
like the one you've hit).

This also should serve the two purposes:
- fall into kernel generic handler for spurious IRQs (by returning
IRQ_NONE below)
- by the way fix current issue in stm32f4

I Hope this is still inline with Jonathan's words earlier ;-)

Best Regards,
Fabrice

>
> if (status & regs->isr_ovr.mask) {

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