linux-kernel - Re: [PATCH v3] iio: adc: ad7606: remove frstdata check for serial mode

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Message-ID: <fabaaa9d7be4193a2bfb5a0476fdcf1ce3117c58.camel@gmail.com>
Date: Wed, 03 Jul 2024 12:42:31 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: Guillaume Stols <gstols@...libre.com>, Lars-Peter Clausen
 <lars@...afoo.de>,  Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Greg Kroah-Hartman <gregkh@...e.de>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, Jonathan
 Cameron <jic23@....ac.uk>, jstephan@...libre.com, dlechner@...libre.com
Subject: Re: [PATCH v3] iio: adc: ad7606: remove frstdata check for serial
 mode

On Tue, 2024-07-02 at 12:52 +0000, Guillaume Stols wrote:
> 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>