On Fri, 3 Jul 2009 23:43:51 -0400
"Yang Fei-AFY095" <fei.yang@xxxxxxxxxxxx> wrote:
>
> >> This is called when we submit urb, for OUT data, I think it's
> >> sufficient for cache consistency. But what I need to know is how
> >> we guarantee the cache consistency for IN data, because the DMA is
> >> going
>
> >> to update the physical memory when receiving data from device,
> >> something has to be done upon completion of the urb.
>
> >Obviously you looked at map_urb_for_dma. Have you also looked at
> unmap_urb_for_dma?
>
> unmap_urb_for_dma -> dma_unmap_single
>
> dma_unmap_single is defined in arch/arm/include/asm/dma-mapping.h as
> following
>
> ------ snip ------
> #ifndef CONFIG_DMABOUNCE
> static inline void
> dma_unmap_single(struct device *dev, dma_addr_t handle, size_t size,
> enum dma_data_direction dir)
> {
> /* nothing to do */
> }
Since the ARM core of TI-OMAP is not cache coherent, it seems
dma_unmap_*() should do something(such as invalidate cache)
instead of nothing.
[CC arm list]
> #else
> extern void dma_unmap_single(struct device *, dma_addr_t, size_t, enum
> dma_data_direction);
> #endif
> ------ snip ------
>
> And CONFIG_DMABOUNCE is not defined in the defconfig.
--
Lei Ming
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