linux-kernel - Re: [PATCH 4/4] spi: s3c64xx: Fix large transfers with DMA

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Message-ID: <2ace1136-25e0-ef6b-8960-29fbc7050e22@linaro.org>
Date:   Mon, 19 Sep 2022 11:43:16 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        broonie@...nel.org, andi@...zian.org
Cc:     kernel@...s.com, alim.akhtar@...sung.com,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/4] spi: s3c64xx: Fix large transfers with DMA

On 16/09/2022 13:39, Vincent Whitchurch wrote:
> The COUNT_VALUE in the PACKET_CNT register is 16-bit so the maximum
> value is 65535.  Asking the driver to transfer a larger size currently
> leads to the DMA transfer timing out.  Fix this by splitting the
> transfer as needed.
> 
> With this, the len>64 KiB tests in spi-loopback-test pass.
> 
> (Note that len==64 KiB tests work even without this patch for some reason.
>  The driver programs 0 to the COUNT_VALUE field in that case, but it's
>  unclear if it's by design, since the hardware documentation doesn't say
>  anything about the behaviour when COUNT_VALUE == 0, so play it safe and
>  split at 65535.)
> 
> Fixes: 230d42d422e7b69 ("spi: Add s3c64xx SPI Controller driver")
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>


Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>


Best regards,
Krzysztof