From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()" Date: Mon, 14 Jan 2019 16:38:20 +0000 Message-ID: <4f7fd8db-33e4-9c8d-2fee-1ca9c98a9276@arm.com> References: <20190114132240.12125-1-m.szyprowski@samsung.com> <20190114160902.GB9218@ulmo> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190114160902.GB9218@ulmo> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org To: Thierry Reding , Marek Szyprowski Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Christoph Hellwig , Russell King , Ben Skeggs , Tobias Jakobi , Bartlomiej Zolnierkiewicz List-Id: iommu@lists.linux-foundation.org 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 >> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()" >> Signed-off-by: Marek Szyprowski >> --- >> 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? 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); }