linux-kernel - Re: [PATCH 2/3] spi: spi-xilinx: Clear dma

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Date:	Wed, 05 Jun 2013 16:39:25 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Mark Brown <broonie@...nel.org>
CC:	Michal Simek <michal.simek@...inx.com>,
	linux-kernel@...r.kernel.org,
	Peter Crosthwaite <pcrost@...inx.com>,
	Grant Likely <grant.likely@...aro.org>,
	spi-devel-general@...ts.sourceforge.net
Subject: Re: [PATCH 2/3] spi: spi-xilinx: Clear dma_mask for xilinx spi controller

On 06/04/2013 07:36 PM, Mark Brown wrote:
> On Tue, Jun 04, 2013 at 04:02:35PM +0200, Michal Simek wrote:
>> From: Michal Simek <monstr@...str.eu>
>>
>> mmc_spi driver tests if dma is available
>> through spi->master->dev.parent->dma_mask.
>> Microblaze supports DMA but xilinx_spi IP doesn't.
>> That's why clear dma_mask in the driver.
> 
>> +	/* clear the dma_mask, to try to disable use of dma */
>> +	master->dev.dma_mask = 0;
>> +
> 
> This looks like a bodge in the wrong place.  Either the device
> registration is incorrect in that it advertises DMA when none is
> available or the SPI driver ought to be offering the MMC driver a more
> sensible way of advertising this limitation.  My first thought is the
> former but I didn't check where dma_mask is getting set.

I have looked at history of this change and we have done it 3 years ago
based on one custom configuration.

It is shame that I don't have hw to test this but there was
something wrong in connection to mmc_spi.c.
I will try to find out hw for this to test but probably
won't be available. :-( And I will just revert this change in my tree.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform



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