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

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Message-ID: <20220507151935.3d3fa270@jic23-huawei>
Date:   Sat, 7 May 2022 15:19:35 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Yannick Brosseau <yannick.brosseau@...il.com>
Cc:     lars@...afoo.de, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, fabrice.gasnier@...s.st.com,
        olivier.moysan@...s.st.com, paul@...pouillou.net,
        linux-iio@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: adc: stm32: Fix check for spurious IRQs on
 STM32F4

On Fri,  6 May 2022 18:56:17 -0400
Yannick Brosseau <yannick.brosseau@...il.com> 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.
> 
> Signed-off-by: Yannick Brosseau <yannick.brosseau@...il.com>

I don't entirely follow the flow here, so will be relying on the driver
maintainers for feedback on this one (even more than normal!)

One question inline.

Jonathan

> ---
>  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)))

For this second condition if it is true, have we not already entered the previous
if (status & regs->isr_ovr.mask) and hence never reached this check?
There is a comment above that to say if we get there over mask should already be
disable. If that's not true for some reason then we should also adjust that check
and the comment.

Or perhaps I'm getting confused by the bracketing and operator precedence.
Should this not be...

> +	if(!(((status & regs->isr_eoc.mask) && (mask & regs->ier_eoc.mask)) ||
> +          ((status & regs->isr_ovr.mask) && (mask & regs->ier_ovr.mask))))
? So as to be the equivalent of the !(status & mask) just checking bits separately.

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