linux-kernel - Re: [PATCH 2/2] iio: at91-sama5d2: Limit requested watermark value to hwfifo size

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Date:   Sat, 4 Jun 2022 16:05:57 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Lars-Peter Clausen <lars@...afoo.de>, linux-iio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Eugen Hristev <eugen.hristev@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>
Subject: Re: [PATCH 2/2] iio: at91-sama5d2: Limit requested watermark value
 to hwfifo size

On Sat, 22 Jan 2022 17:04:47 +0000
Jonathan Cameron <jic23@...nel.org> wrote:

> On Mon, 17 Jan 2022 10:25:12 +0000
> Paul Cercueil <paul@...pouillou.net> wrote:
> 
> > Instead of returning an error if the watermark value is too high, which
> > the core will silently ignore anyway, limit the value to the hardware
> > FIFO size; a lower-than-requested value is still better than using the
> > default, which is usually 1.  
> 
> There is another potential error condition in this function which will
> also be ignored by the core.
> 
> As such whilst I agree this is a sensible thing to do in this
> particular case I think we should also be handling the error in the core.
> 
> I think it would be better to clean that up at the same time
> as these improvements - particularly as I'd guess you have a convenient
> test setup to check the error unwind is correct?

Hi Paul,

I was trawling through patchwork and realised this one is stalled.

Thoughts on the above?

Thanks,

Jonathan

> 
> Thanks,
> 
> Jonathan
> 
> > 
> > Cc: Eugen Hristev <eugen.hristev@...rochip.com>
> > Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>
> > Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>
> > Cc: Ludovic Desroches <ludovic.desroches@...rochip.com>
> > Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> > ---
> >  drivers/iio/adc/at91-sama5d2_adc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
> > index 854b1f81d807..5cc84f4a17bb 100644
> > --- a/drivers/iio/adc/at91-sama5d2_adc.c
> > +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> > @@ -1752,7 +1752,7 @@ static int at91_adc_set_watermark(struct iio_dev *indio_dev, unsigned int val)
> >  	int ret;
> >  
> >  	if (val > AT91_HWFIFO_MAX_SIZE)
> > -		return -EINVAL;
> > +		val = AT91_HWFIFO_MAX_SIZE;
> >  
> >  	if (!st->selected_trig->hw_trig) {
> >  		dev_dbg(&indio_dev->dev, "we need hw trigger for DMA\n");  
>