Hi Robin, On 2019-01-14 17:38, Robin Murphy wrote: > On 14/01/2019 16:09, Thierry Reding wrote: >> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote: >>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3. >>> >>> That patch broke IOMMU support for devices, which fails to probe for >>> the >>> first time and use deferred probe approach. When non-NULL dma_ops is >>> set >>> in arm_iommu_detach_device(), the given device later ignored by >>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops. >>> >>> Reported-by: Tobias Jakobi <tjak...@math.uni-bielefeld.de> >>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in >>> arm_iommu_detach_device()" >>> Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com> >>> --- >>> arch/arm/mm/dma-mapping.c | 12 ++++++------ >>> 1 file changed, 6 insertions(+), 6 deletions(-) >> >> Can you point out exactly what drivers break because of this change? We >> need to find a solution that works for everyone. Reverting is only >> marginally useful because somebody will just end up wanting to revert >> the revert because a different driver is now broken. > > At first glance, it sounds like what we really want is for > arch_teardown_iommu_ops() to completely clear any ops that > arch_setup_dma_ops() installed - does the below suffice?
I've initially also thought about similar fix, but then I found the commit 1874619a7df4b14b23b14877e705ae15325773e3, which was the source of this problem. Robin: do you plan to send this fix as a complete patch or do you want me to resend it with the above commit message and your's suggested-by? > > Robin. > > ----->8----- > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index f1e2922e447c..1e3e08a1c456 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev) > return; > > arm_teardown_iommu_dma_ops(dev); > + /* Let arch_setup_dma_ops() start again from scratch upon > re-probe */ > + set_dma_ops(dev, NULL); > } > > Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
