Re: [RFC PATCH powerpc] Fix a dma_mask issue of vio

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Thu, Nov 21, 2013 at 11:01:42AM +1100, Benjamin Herrenschmidt wrote:
> On Wed, 2013-11-20 at 23:23 +0000, Russell King - ARM Linux wrote:
> > Li Zong's patch works around the issue of a failing dma_set_mask(),
> > but as I've already said elsewhere, the real fix is to get whatever
> > created the struct device to initialise the dev->dma_mask with a
> > bus default.
> > 
> > Using dma_coerce_xxx() merely makes the problem "go away" papering
> > over the issue - it's fine to do it this way, but someone should still
> > fix the broken code creating these devices...
> 
> Ok, they are created by the vio bus core, so it should be doing the
> job here of setting the dma_mask pointer to a proper value.
> 
> Li, can you take care of that ? Look at other bus types we have in
> there such as the macio bus etc...

Oh, hang on a moment, this is the "bus" code.

In which case, the question becomes: do vio devices ever need to have
a separate streaming DMA mask from a coherent DMA mask?  If not, then
something like the following is what's needed here, and I should've
never have used dma_set_mask_and_coherent().

dma_set_mask_and_coherent() (and the other dma_set_mask() functions)
are really supposed to be used by drivers only.

 arch/powerpc/kernel/vio.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c
index e7d0c88f621a..d771778f398e 100644
--- a/arch/powerpc/kernel/vio.c
+++ b/arch/powerpc/kernel/vio.c
@@ -1419,7 +1419,8 @@ struct vio_dev *vio_register_device_node(struct device_node *of_node)
 
 		/* needed to ensure proper operation of coherent allocations
 		 * later, in case driver doesn't set it explicitly */
-		dma_set_mask_and_coherent(&viodev->dev, DMA_BIT_MASK(64));
+		viodev->dev.coherent_dma_mask = DMA_BIT_MASK(64);
+		viodev->dev.dma_mask = &viodev->dev.coherent_dma_mask;
 	}
 
 	/* register with generic device framework */