On Fri, Feb 28, 2020 at 3:51 PM Michael Walle [off-list ref] wrote:

Am 2020-02-28 12:46, schrieb Michael Walle:

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Hi Rob, Hi Leo,

Am 2020-02-28 00:03, schrieb Rob Herring:

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On Thu, Feb 27, 2020 at 4:49 PM Li Yang [off-list ref] wrote:

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On Thu, Feb 27, 2020 at 4:35 PM Rob Herring [off-list ref]
wrote:

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On Fri, Feb 21, 2020 at 11:48 AM Michael Walle [off-list ref] wrote:

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The DMA channel might not be available at the first probe time. This is
esp. the case if the DMA controller has an IOMMU mapping.

Use the new dma_request_chan() API and handle EPROBE_DEFER errors. Also
reorder the code a bit, so that we don't prepare the whole UART just to
determine that the DMA channel is not ready yet and we have to undo all
the stuff. Try to map the DMA channels earlier.

Changing this means you never probe successfully if you boot a kernel
with the DMA driver disabled (or it's IOMMU disabled). Some other
drivers request DMA in open() and can work either way.

Oh, I see.

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We got this exact issue previously with another driver.  When the

What driver is it? I've been working on the i2c-mxs.c driver which has

whoops, i2c-imx.c, not i2c-mxs.c

Ya.  Same one.  I have added CONFIG_FSL_EDMA into the arm64/defconfig
as a workaround.

Regards,
Leo

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