linux-kernel - Re: [PATCH 4.19 182/267] spi: dw: Return any value retrieved from the dma

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Message-ID: <20200629142606.GR1931@sasha-vm>
Date:   Mon, 29 Jun 2020 10:26:06 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Ralph Siemsen <ralph.siemsen@...aro.org>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Pavel Machek <pavel@...x.de>,
        Serge Semin <fancer.lancer@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Georgy Vlasov <Georgy.Vlasov@...kalelectronics.ru>,
        Ramil Zaripov <Ramil.Zaripov@...kalelectronics.ru>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Feng Tang <feng.tang@...el.com>,
        Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
        devicetree@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 4.19 182/267] spi: dw: Return any value retrieved from
 the dma_transfer callback

On Fri, Jun 26, 2020 at 11:18:00AM -0400, Ralph Siemsen wrote:
>Hi Serge, Pavel, Greg,
>
>On Mon, Jun 22, 2020 at 11:51:21PM +0300, Serge Semin wrote:
>>Hello Pavel
>>
>>On Fri, Jun 19, 2020 at 11:07:19PM +0200, Pavel Machek wrote:
>>
>>>Mainline patch simply changes return value, but code is different in
>>>v4.19, and poll_transfer will now be avoided when dws->dma_mapped. Is
>>>that a problem?
>>
>>Actually no.) In that old 4.19 context it's even better to return straight away
>>no matter what value is returned by the dma_transfer() callback.
>
>This patch changes the return dma_transfer return value from 0 to 1, 
>however it was only done in spi-dw-mid.c func mid_spi_dma_transfer().
>
>There is an identical function in spi-dw-mmio.c that needs the same 
>treatment, otherwise access to the SPI device becomes erratic and even 
>causes kernel to hang. Guess how I found this ;-)
>
>So the following patch is needed as well, at least in 4.9 and 4.19, I 
>did not check/test other versions. Mainline does not need this, since 
>the code seems to have been refactored to avoid the duplication.
>
>Regards,
>-Ralph
>
>diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
>index c563c2815093..99641c485288 100644
>--- a/drivers/spi/spi-dw-mmio.c
>+++ b/drivers/spi/spi-dw-mmio.c
>@@ -358,7 +358,7 @@ static int mmio_spi_dma_transfer(struct dw_spi *dws, struct spi_transfer *xfer)

Um, I can't find this function anywhere... what am I missing?

-- 
Thanks,
Sasha