Re: [Xen-devel] cubieboard2's sd/mmc driver on xen about DMA read data error

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 2 Apr 2014, Ian Campbell wrote:
> On Wed, 2014-04-02 at 00:10 +0800, æç wrote:
> > Hi all,
> 
> Hello,
> 
> >      I have got this kernel with mmc driver on cubieboard2 from :
> > https://github.com/jwrdegoede/linux-sunxi.git  (test branch) . 
> >      I  have made the Xen's Dom0 configuration according
> > this :http://wiki.xenproject.org/wiki/Mainline_Linux_Kernel_Configs.
> > and the kernel can be booted by Xen4.4.
> >      The question we met is that some CMD can be
> > accepted(CMD7,CMD0 ....) and but some can't(CMD52,CMD5,CMD51). 
> >      We have found that the CMD51 is attempted to read the data from
> > SD card to memory through DMA , so we replaced all the dma_ops with
> > xen_dma_ops , where it is in struct "dma_map_ops xen_swiotlb_dma_ops"
> > in arch/arm/xen/mm.c.
> 
> Do I understand correctly that you have solved the issue by doing this?

Where did you replace the dma_ops with xen_dma_ops? Could you please
send out a patch so that I can understand what you modified exactly?

Keep in mind that for Dom0, get_dma_ops should already return
xen_dma_ops (see arch/arm/include/asm/dma-mapping.h:get_dma_ops), so in
theory you should already be getting the xen_dma_ops without having to
do anything.

So maybe the MMC driver is calling the arm_dma_ops functions directly
without going through get_dma_ops? It seems unlikely to me.
Can you point me to the right MMC driver in Linux that you are using?

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