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

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Message-ID: <20240907155139.67a296c7@jic23-huawei>
Date: Sat, 7 Sep 2024 15:51:39 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Alexandru Ardelean <aardelean@...libre.com>
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,  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.