From: broonie@kernel.org (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 3/6] spi: davinci: use rx buffer as dummy tx buffer
Date: Wed, 15 Mar 2017 19:35:30 +0000 [thread overview]
Message-ID: <20170315193530.fjguqfb6vjd7kfey@sirena.org.uk> (raw)
In-Reply-To: <1487872921-26628-4-git-send-email-fisaksen@baylibre.com>
On Thu, Feb 23, 2017 at 07:01:58PM +0100, Frode Isaksen wrote:
> When doing rx-only transfer, the transfer will fail
> if the number of SG entries exceeds 20.
> This happens because the eDMA DMA engine is limited
> to 20 SG entries in one transaction, and when the
> DMA transcation is resumed (which takes > 150us),
> rx errors occurs because the slave is still transmitting.
> Fix this by using the rx buffer as the dummy tx buffer,
> so that resuming the rx transcation happens at the same
> time as resuming the tx transcation.
Please submit a followup patch adding a comment explaing what's going
in the actual code as someone's going to clean this up at some point.
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next prev parent reply other threads:[~2017-03-15 19:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-23 18:01 [PATCH v3 0/6] Enable DMA for daVinci SPI controller Frode Isaksen
2017-02-23 18:01 ` [PATCH v3 1/6] spi: davinci: Use SPI framework to handle DMA mapping Frode Isaksen
2017-03-07 14:22 ` Applied "spi: davinci: Use SPI framework to handle DMA mapping" to the spi tree Mark Brown
2017-02-23 18:01 ` [PATCH v3 2/6] spi: davinci: enable DMA when channels are defined in DT Frode Isaksen
2017-02-23 18:01 ` [PATCH v3 3/6] spi: davinci: use rx buffer as dummy tx buffer Frode Isaksen
2017-03-15 19:35 ` Mark Brown [this message]
2017-02-23 18:01 ` [PATCH v3 4/6] spi: davinci: do not use DMA if transfer length is less than 16 Frode Isaksen
2017-03-15 19:37 ` Applied "spi: davinci: do not use DMA if transfer length is less than 16" to the spi tree Mark Brown
2017-02-23 18:02 ` [PATCH v3 5/6] spi: davinci: do not use DMA for vmalloc'ed buffers Frode Isaksen
2017-03-15 19:37 ` Applied "spi: davinci: do not use DMA for vmalloc'ed buffers" to the spi tree Mark Brown
2017-02-23 18:02 ` [PATCH v3 6/6] spi: loopback-test: add option to use vmalloc'ed buffers Frode Isaksen
2017-03-16 14:11 ` Applied "spi: loopback-test: add option to use vmalloc'ed buffers" to the spi tree Mark Brown
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