* 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
