[Linux-stm32] [PATCH 2/2] iio: adc: stm32: Fix check for spurious IRQs on STM32F4

[Brosseau, Yannick]

On Fri, May 13, 2022 at 9:14 AM Fabrice Gasnier <fabrice.gasnier at foss.st.com>
wrote:

> 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 at 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 agree with this. I was a bit unsure if this code was necessary. I ran my
systems with those line removed for a few months without issues.
I'll spin up an updated patchset.

Yannick
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