linux-kernel - Re: [PATCH v5 1/9] iio: adc: ad7606: remove frstdata check for serial mode

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Message-ID: <CA+GgBR8URUmcru0Q=ut8gVdEO=KeVOQgzwWPr7bz1ceiSJXdEA@mail.gmail.com>
Date: Sat, 7 Sep 2024 20:58:38 +0300
From: Alexandru Ardelean <aardelean@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, krzk+dt@...nel.org, robh@...nel.org, 
	lars@...afoo.de, michael.hennerich@...log.com, gstols@...libre.com, 
	Nuno Sa <nuno.sa@...log.com>, Stable@...r.kernel.org, 
	Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v5 1/9] iio: adc: ad7606: remove frstdata check for serial mode

On Sat, Sep 7, 2024 at 5:51 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Sat,  7 Sep 2024 09:50:34 +0300
> Alexandru Ardelean <aardelean@...libre.com> wrote:
>
> > From: Guillaume Stols <gstols@...libre.com>
> >
> > The current implementation attempts to recover from an eventual glitch
> > in the clock by checking frstdata state after reading the first
> > channel's sample: If frstdata is low, it will reset the chip and
> > return -EIO.
> >
> > This will only work in parallel mode, where frstdata pin is set low
> > after the 2nd sample read starts.
> >
> > For the serial mode, according to the datasheet, "The FRSTDATA output
> > returns to a logic low following the 16th SCLK falling edge.", thus
> > after the Xth pulse, X being the number of bits in a sample, the check
> > will always be true, and the driver will not work at all in serial
> > mode if frstdata(optional) is defined in the devicetree as it will
> > reset the chip, and return -EIO every time read_sample is called.
> >
> > Hence, this check must be removed for serial mode.
> >
> > Fixes: b9618c0cacd7 ("staging: IIO: ADC: New driver for AD7606/AD7606-6/AD7606-4")
> > Signed-off-by: Guillaume Stols <gstols@...libre.com>
> > Reviewed-by: Nuno Sa <nuno.sa@...log.com>
> > Link: https://patch.msgid.link/20240702-cleanup-ad7606-v3-1-18d5ea18770e@baylibre.com
> > Cc: <Stable@...r.kernel.org>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reference the fix patch in your cover letter, but don't include it in the series.
>
> I'll just get confused when I pick this up.

ack
will do