Hi Russell,

On Thursday 25 May 2017 16:05:41 Russell King - ARM Linux wrote:

On Wed, May 24, 2017 at 02:26:13PM +0300, Laurent Pinchart wrote:

quoted

Again, the patch I propose is the simplest v4.12-rc fix I can think of,
short of reverting your complete IOMMU probe deferral patch series. Let's
focus on the v4.12-rc fix, and then discuss how to move forward in v4.13
and beyond.

Except, I don't think it fixes the problem that Sricharan is trying to
fix, namely that of DMA ops that have been setup, torn down, and are
trying to be re-setup again.

You're right, it's two separate problems, and we need to fix them both.

The issue here is that results in a stale setup, because the dma_ops are
left in-place from the first iommu setup, but the iommu mapping has been
disposed of.

Your patch only avoids the problem of tearing down someone else's DMA
ops.  We need a combination of both patches together.

Yes exactly. I should read e-mails to the end before starting typing the reply 
:-)

What needs to happen for Sricharan's problem to be resolved is:

1. move all of __arm_iommu_detach_device() into arm_iommu_detach_device().
2. replace the __arm_iommu_detach_device() call in
arm_teardown_iommu_dma_ops() with arm_iommu_detach_device().

as I don't see any need to have a different order in
arm_teardown_iommu_dma_ops().

-- 
Regards,

Laurent Pinchart