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From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Kweh Hock Leong <hock.leong.kweh@intel.com>,
        Eric Miao <eric.y.miao@gmail.com>,
        Russell King <linux@arm.linux.org.uk>,
        Haojian Zhuang <haojian.zhuang@gmail.com>,
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        Chew Chiau Ee <chiau.ee.chew@intel.com>,
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        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>
Subject: Re: [PATCH] spi/pxa2xx-pci: Enable DMA binding through device name
Date: Thu, 24 Jul 2014 13:42:10 +0200
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On Thursday 24 July 2014 18:01:51 Kweh Hock Leong wrote:
> From: "Chew, Chiau Ee" <chiau.ee.chew@intel.com>
> 
> 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 <chiau.ee.chew@intel.com>
> Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@intel.com>

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.

	Arnd