Re: [PATCH] spi/pxa2xx-pci: Enable DMA binding through device name

From: Arnd Bergmann
Date: Thu Jul 24 2014 - 07:45:14 EST

On Thursday 24 July 2014 18:01:51 Kweh Hock Leong wrote:
> From: "Chew, Chiau Ee" <>
> Intel LPSS Baytrail supports two DMA controllers and SPI is only
> using one of the DMA controller. During DMA channel request,
> we need to ensure the requested Tx and Rx channels are from the correct
> DMA controller. Thus, we add extra checking in filter callback funtion
> by matching against the DMA controller device name.
> Signed-off-by: Chew, Chiau Ee <>
> Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@xxxxxxxxx>

I'm confused. Doesn't Bay Trail use ACPI to do the DMA
engine configuration? That should set find the right device/chan_id/slave_id
combination without any interaction, through the use of dma_request_slave_channel.

On a related note, there seems to be a bug in this driver, which
attempts to set the slave_id through dmaengine_slave_config(), which
is wrong in both cases, ACPI and filter functions.

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