Re: [PATCH 1/8] ARM: OMAP: fix DMA vs memory ordering

[Tony Lindgren <tony@xxxxxxxxxxx>]

* Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [120423 07:22]:
> On Fri, Apr 20, 2012 at 03:22:33PM -0700, Tony Lindgren wrote:
> > * Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> [120418 03:14]:
> > > Using coherent DMA memory with the OMAP DMA engine results in
> > > unpredictable behaviour due to memory ordering issues; as things stand,
> > > there is no guarantee that data written to coherent DMA memory will be
> > > visible to the DMA hardware.
> > > 
> > > This is because the OMAP dma_write() accessor contains no barriers,
> > > necessary on ARMv6 and above.  The effect of this can be seen in comments
> > > in the OMAP serial driver, which incorrectly talks about cache flushing
> > > for the coherent DMA stuff.
> > > 
> > > Rather than adding barriers to the accessors, add it in the DMA support
> > > code just before we enable DMA, and just after we disable DMA.  This
> > > avoids having barriers for every DMA register access.
> > > 
> > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
> > 
> > Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
> 
> Would you like me to push this upstream on my next -rc push (with a
> stable tag?)

Yes sounds good to me.

Regards,

Tony
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