linux-kernel - Re: [PATCH 2/2] ARM: dts: imx7: add DMA properties for ECSPI

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Date:   Mon, 11 Feb 2019 19:34:19 -0200
From:   Fabio Estevam <festevam@...il.com>
To:     Trent Piepho <tpiepho@...inj.com>
Cc:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-imx@....com" <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "stefan@...er.ch" <stefan@...er.ch>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "fabio.estevam@....com" <fabio.estevam@....com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
Subject: Re: [PATCH 2/2] ARM: dts: imx7: add DMA properties for ECSPI

Hi Trent,

On Mon, Feb 11, 2019 at 6:44 PM Trent Piepho <tpiepho@...inj.com> wrote:

> I've had more time to test.
>
> Without DMA, I can reload my FPGA hundreds of times and get days of
> uptime using linux-next.
>
> With DMA, loading is unreliable.  The higher the SPI speed, the less
> reliable it is.  Unfortunately, it's hard to duplicate the problem with
> a small amount of data, and with a large amount of data I can't examine
> it in depth enough to determine if the problem is related to SPI bus
> timing or IMX sDMA sending the wrong bytes to the spi controller.
>
> Using DMA with SPI causes kernel panics.  Not always immediately, but
> after using DMA it's a smaller of minutes before something crashes.
> The backtraces are all over the place and don't usually point back into
> SPI.  It does seem like they usually hit something has allocated or is
> allocating DMA memory.

Did you test with an external SDMA firmware or with the ROM SDMA firmware?

Just trying to understand if the SDMA firmware plays a role on this
behavior or not.