linux-kernel - Re: [PATCH V8 2/5] i2c: tegra: Add Bus Clear Master Support

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Date:   Thu, 31 Jan 2019 18:16:36 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com,
        mkarthik@...dia.com, smohammed@...dia.com, talho@...dia.com
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH V8 2/5] i2c: tegra: Add Bus Clear Master Support

31.01.2019 9:16, Sowjanya Komatineni пишет:
> Bus clear feature of tegra i2c controller helps to recover from
> bus hang when i2c master loses the bus arbitration due to the
> slave device holding SDA LOW continuously for some unknown reasons.
> 
> Per I2C specification, the device that held the bus LOW should
> release it within 9 clock pulses.
> 
> During bus clear operation, Tegra I2C controller sends 9 clock
> pulses and terminates the transaction with STOP condition.
> Upon successful bus clear operation, bus goes to idle state and
> driver retries the transaction.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  [V5/V6/V7/V8]: Same as V4
>  [V4]: Added I2C Bus Clear support patch to this version of series.
> 
 
I haven't checked all of the bits in this patch, but at least -EAGAIN should work as expected on older Tegra's:

Reviewed-by: Dmitry Osipenko <digetx@...il.com>