From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 17 Feb 2016 10:19:17 +0000 Subject: [PATCH] ARM64: dma-mapping: fix handling of devices registered before arch_initcall In-Reply-To: <56C41BE6.5000203@samsung.com> References: <1455632084-14666-1-git-send-email-m.szyprowski@samsung.com> <56C37317.9020104@arm.com> <56C41BE6.5000203@samsung.com> Message-ID: <56C44925.6090406@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17/02/16 07:06, Marek Szyprowski wrote: > Hello, > > On 2016-02-16 20:05, Robin Murphy wrote: >> On 16/02/16 14:14, Marek Szyprowski wrote: >>> This patch ensures that devices, which got registered before >>> arch_initcall >>> will be handled correctly by IOMMU-based DMA-mapping code. >>> >>> Signed-off-by: Marek Szyprowski >>> --- >>> arch/arm64/mm/dma-mapping.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c >>> index 573b1e6..ce6019f 100644 >>> --- a/arch/arm64/mm/dma-mapping.c >>> +++ b/arch/arm64/mm/dma-mapping.c >>> @@ -928,6 +928,10 @@ static int __init __iommu_dma_init(void) >>> ret = register_iommu_dma_ops_notifier(&platform_bus_type); >>> if (!ret) >>> ret = register_iommu_dma_ops_notifier(&amba_bustype); >>> + >>> + /* handle devices queued before this arch_initcall */ >>> + if (!ret) >>> + __iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL); >> >> Hmm, surely unless *all* the devices on the relevant buses are created >> before arch_initcall level, then the next one is going to kick off the >> notifier to walk the whole list anyway. Have you seen this being a >> problem in practice? > > Yes, I've observed such situation, that's why I've posted this patch. I was > really surprised that this code doesn't handle all cases. Ok, fair enough - I guess I just didn't consider that being a likely possibility. Since I am a fan of correctness: Acked-by: Robin Murphy Thanks, Robin. > > Best regards