linux-kernel - Re: [PATCH 3.14 37/96] iio: mxs-lradc: only update the buffer when its conversions have finished

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Date:	Thu, 19 Mar 2015 14:15:20 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Kristina Martšenko <kristina.martsenko@...il.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Marek Vasut <marex@...x.de>,
	Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH 3.14 37/96] iio: mxs-lradc: only update the buffer when
 its conversions have finished

On Thu, Mar 19, 2015 at 01:36:13AM +0200, Kristina Martšenko wrote:
> On 16/03/15 16:09, Greg Kroah-Hartman wrote:
> > 3.14-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Kristina Martšenko <kristina.martsenko@...il.com>
> > 
> > commit 89bb35e200bee745c539a96666e0792301ca40f1 upstream.
> > 
> > Using the touchscreen while running buffered capture results in the
> > buffer reporting lots of wrong values, often just zeros. This is because
> > we push readings to the buffer every time a touchscreen interrupt
> > arrives, including when the buffer's own conversions have not yet
> > finished. So let's only push to the buffer when its conversions are
> > ready.
> > 
> > Signed-off-by: Kristina Martšenko <kristina.martsenko@...il.com>
> > Reviewed-by: Marek Vasut <marex@...x.de>
> > Signed-off-by: Jonathan Cameron <jic23@...nel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > ---
> >  drivers/staging/iio/adc/mxs-lradc.c |    7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > --- a/drivers/staging/iio/adc/mxs-lradc.c
> > +++ b/drivers/staging/iio/adc/mxs-lradc.c
> > @@ -1160,9 +1160,12 @@ static irqreturn_t mxs_lradc_handle_irq(
> >  	}
> >  
> >  	if (iio_buffer_enabled(iio))
> > -		iio_trigger_poll(iio->trig, iio_get_time_ns());
> > -	else if (reg & LRADC_CTRL1_LRADC_IRQ(0))
> > +	if (iio_buffer_enabled(iio)) {
> > +		if (reg & lradc->buffer_vchans)
> > +			iio_trigger_poll(iio->trig, iio_get_time_ns());
> > +	} else if (reg & LRADC_CTRL1_LRADC_IRQ(0)) {
> >  		complete(&lradc->completion);
> > +	}
> >  
> >  	mxs_lradc_reg_clear(lradc, reg & clr_irq, LRADC_CTRL1);
> 
> I think something got messed up here, this now has both these lines:
> 
> 	if (iio_buffer_enabled(iio))
> 	if (iio_buffer_enabled(iio)) {
> 
> which makes the 'else' case unreachable, and breaks reading the ADC
> through sysfs. It should just be the second line.
> 
> Greg, can you fix it up for the next version? Let me know if I need to
> do something. And sorry for not looking at this sooner.

Ah crap, I messed this up when doing the backport, I'll fix it up, it's
my fault here.

Thanks for noticing this, I'll go make up a fix now...

thanks,

greg k-h
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