linux-kernel - RE: [RFC PATCH 0/3] spi/xilinx: Merge OF and non-OF drivers

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Message-ID: <ec622bb7-57d1-4aa2-80f1-65fa4b3fa7eb@VA3EHSMHS033.ehs.local>
Date:	Mon, 8 Nov 2010 07:34:05 -0700
From:	John Linn <John.Linn@...inx.com>
To:	<monstr@...str.eu>, <grant.likely@...retlab.ca>
CC:	<spi-devel-general@...ts.sourceforge.net>,
	<richard.rojfors@...ean-labs.com>, <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH 0/3] spi/xilinx: Merge OF and non-OF drivers

> -----Original Message-----
> From: Michal Simek [mailto:monstr@...str.eu]
> Sent: Monday, November 08, 2010 6:29 AM
> To: grant.likely@...retlab.ca
> Cc: spi-devel-general@...ts.sourceforge.net; richard.rojfors@...ean-labs.com; John Linn; linux-
> kernel@...r.kernel.org
> Subject: Re: [RFC PATCH 0/3] spi/xilinx: Merge OF and non-OF drivers
> 
> Hi Grant,
> 
> Grant Likely wrote:
> > Since of_platform_bus_type has been merged with the platform_bus_type,
> > a single platform driver can now support both use cases.  This patch
> > series merges the two halves of the xilinx_spi device driver.
> >
> > Compile tested only.  I haven't booted this yet.
> 
> I have tested it on sp605 and works well. Have you added that patches
> to your repository? Or are they somewhere else? Who is responsible for?
> 
> I would like to also discuss one change which is related mmc_spi kernel driver.
> Let me describe the problem. Microblaze can use dma in all addresses
> that's why dma_mask is setup to 0xffffffff in of_platform_device_create.
> Xilinx spi driver doesn't support dma but mmc_spi driver is checking dma_mask in parent device
> which is xilinx spi driver.
> 
> Here is the corresponding the part of code (Expect dma_mask=zero for no dma operations).
> mmc_spi.c:~1395
> 	if (spi->master->dev.parent->dma_mask) {
> 		struct device	*dev = spi->master->dev.parent;
> 
> 		host->dma_dev = dev;
> 
> 
> Based on this one our customer came with the following solution to setup
> dma_mask in xilinx_spi to zero and then mmc_spi doesn't setup dma operation.
> 
> I think that this is nice solution but I would like to be sure that I didn't miss anything.
> After that i will create proper patch with description.

Seems reasonable to me.

Thanks,
John

> 
> 
> diff --git a/drivers/spi/xilinx_spi.c b/drivers/spi/xilinx_spi.c
> index 7adaef6..3612e1b 100644
> --- a/drivers/spi/xilinx_spi.c
> +++ b/drivers/spi/xilinx_spi.c
> @@ -519,6 +519,9 @@ static int __devinit xilinx_spi_probe(struct platform_device *dev)
>         }
> 
>         platform_set_drvdata(dev, master);
> +       /* clear the dma_mask, to try to disable use of dma */
> +       dev->dev.dma_mask = 0;
> +
>         return 0;
>  }
> 
> 
> Thanks,
> Michal
> 
> 
> --
> Michal Simek, Ing. (M.Eng)
> w: www.monstr.eu p: +42-0-721842854
> Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
> Microblaze U-BOOT custodian


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