Re: [PATCH] mpt2sas: Fall back to 64 bit coherent mask if 64 bit DMA / 32 bit coherent mask not supported

On Tuesday 12 May 2015 18:24:43 Brian King wrote:

Commit 5fb1bf8aaa832e1e9ca3198de7bbecb8eff7db9c broke 64 bit DMA for mpt2sas on Power.
That commit changed the sequence for setting up the DMA and coherent DMA masks so
that during initialization the driver requests a 64 bit DMA mask and a 32 bit consistent
DMA mask, then later requests a 64 bit consistent DMA mask. The Power architecture does
not currently support this, which results in always falling back to a 32 bit DMA window,
which has a negative impact on performance. Tweak this algorithm slightly so that
if requesting a 32 bit consistent mask fails after we've successfully set a 64 bit
DMA mask, just try to get a 64 bit consistent mask. This should preserve existing
behavior on platforms that support mixed mask setting and restore previous functionality
to those that do not.

Signed-off-by: Brian King <redacted>

I believe the way the API is designed, it should guarantee that after dma_set_mask()
succeeds for a device, dma_set_coherent_mask() with the same mask will also succeed.

Could you just call dma_set_mask_and_coherent() here to avoid that complex logic?

	Arnd