linux-kernel - Re: [PATCH v3 9/9] i2c: tegra: Check DMA completion status in addition to left time

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Message-ID: <72761d8598d248fbab872ad844b14aab@HQMAIL105.nvidia.com>
Date:   Tue, 7 Jan 2020 12:39:22 +0000
From:   Thierry Reding <treding@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "Mikko Perttunen" <cyndis@...si.fi>,
        Wolfram Sang <wsa@...-dreams.de>, <linux-i2c@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 9/9] i2c: tegra: Check DMA completion status in
 addition to left time

On Mon, 06 Jan 2020 04:04:23 +0300, Dmitry Osipenko wrote:
> It is more robust to check completion status in addition to the left time
> in a case of DMA transfer because transfer's completion happens in two
> phases [one is ISR, other is tasklet] and thus it is possible that DMA is
> completed while I2C completion awaiting times out because of the deferred
> notification done by the DMA driver. The DMA completion status becomes
> 100% actual after DMA synchronization. This fixes spurious DMA timeouts
> when system is under load.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

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