linux-kernel - Re: [PATCH] dmaengine: imx-sdma: fix context cache

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Message-ID: <20200224165752.GE2618@vkoul-mobl>
Date:   Mon, 24 Feb 2020 22:27:52 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Fabio Estevam <festevam@...il.com>
Cc:     Martin Fuzzey <martin.fuzzey@...wbird.group>,
        dmaengine@...r.kernel.org, stable <stable@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        Robin Gong <yibin.gong@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: imx-sdma: fix context cache

On 29-01-20, 17:19, Fabio Estevam wrote:
> Hi Martin,
> 
> Thanks for the fix.
> 
> On Wed, Jan 29, 2020 at 10:41 AM Martin Fuzzey
> <martin.fuzzey@...wbird.group> wrote:
> >
> > There is a DMA problem with the serial ports on i.MX6.
> >
> > When the following sequence is performed:
> >
> > 1) Open a port
> > 2) Write some data
> > 3) Close the port
> > 4) Open a *different* port
> > 5) Write some data
> > 6) Close the port
> >
> > The second write sends nothing and the second close hangs.
> > If the first close() is omitted it works.
> >
> > Adding logs to the the UART driver shows that the DMA is being setup but
> > the callback is never invoked for the second write.
> >
> > This used to work in 4.19.
> >
> > Git bisect leads to:
> >         ad0d92d: "dmaengine: imx-sdma: refine to load context only once"
> >
> > This commit adds a "context_loaded" flag used to avoid unnecessary context
> > setups.
> > However the flag is only reset in sdma_channel_terminate_work(),
> > which is only invoked in a worker triggered by sdma_terminate_all() IF
> > there is an active descriptor.
> >
> > So, if no active descriptor remains when the channel is terminated, the
> > flag is not reset and, when the channel is later reused the old context
> > is used.
> >
> > Fix the problem by always resetting the flag in sdma_free_chan_resources().
> >
> > Fixes: ad0d92d: "dmaengine: imx-sdma: refine to load context only once"
> 
> Nit: in the Fixes tag we use 12 digits for the commit ID and the
> Subject is enclosed by parenthesis.
> 
> The preferred format would be:
> 
> Fixes: ad0d92d7ba6a ("dmaengine: imx-sdma: refine to load context only once")
> 
> Reviewed-by: Fabio Estevam <festevam@...il.com>

Applied, with updated Fixes line. Thanks

-- 
~Vinod