On Wed, Apr 18, 2012 at 11:17:33AM +0100, Russell King - ARM Linux wrote: > On Wed, Apr 18, 2012 at 01:15:20PM +0300, Felipe Balbi wrote: > > On Wed, Apr 18, 2012 at 11:10:35AM +0100, Russell King wrote: > > > 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> > > > > cool, should this go to stable too ? > > Has anyone seen a problem (other than me when trying to get DMA engine > working with omap-serial transmit paths) ? probably not since omap-serial isn't using DMA anyway. Nevermind -- balbi
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