linux-kernel - Re: [PATCH] i2c: tegra: Fix NACK error handling

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Date:   Mon, 9 Jul 2018 16:01:56 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Laxman Dewangan <ldewangan@...dia.com>,
        Shardar Shariff Md <smohammed@...dia.com>,
        linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] i2c: tegra: Fix NACK error handling

On Tue, Jul 03, 2018 at 09:55:43AM +0100, Jon Hunter wrote:
> On Tegra30 Cardhu the PCA9546 I2C mux is not ACK'ing I2C commands on
> resume from suspend (which is caused by the reset signal for the I2C
> mux not being configured correctl). However, this NACK is causing the
> Tegra30 to hang on resuming from suspend which is not expected as we
> detect NACKs and handle them. The hang observed appears to occur when
> resetting the I2C controller to recover from the NACK.
> 
> Commit 77821b4678f9 ("i2c: tegra: proper handling of error cases") added
> additional error handling for some error cases including NACK, however,
> it appears that this change conflicts with an early fix by commit
> f70893d08338 ("i2c: tegra: Add delay before resetting the controller
> after NACK"). After commit 77821b4678f9 was made we now disable 'packet
> mode' before the delay from commit f70893d08338 happens. Testing shows
> that moving the delay to before disabling 'packet mode' fixes the hang
> observed on Tegra30. The delay was added to give the I2C controller
> chance to send a stop condition and so it makes sense to move this to
> before we disable packet mode. Please note that packet mode is always
> enabled for Tegra.
> 
> Fixes: 77821b4678f9 ("i2c: tegra: proper handling of error cases")
> 
> Cc: stable@...r.kernel.org
> 
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)

Seems sensible:

Acked-by: Thierry Reding <treding@...dia.com>

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