From mboxrd@z Thu Jan  1 00:00:00 1970
From: sricharan@codeaurora.org (Sricharan)
Date: Thu, 27 Oct 2016 08:02:15 +0530
Subject: [PATCH] arm64: Remove pointless WARN_ON in DMA teardown
In-Reply-To: <74f5ae2ead8bb8fa9fabcf88b5962885b29eb2d5.1477505971.git.robin.murphy@arm.com>
References: <74f5ae2ead8bb8fa9fabcf88b5962885b29eb2d5.1477505971.git.robin.murphy@arm.com>
Message-ID: <004801d22ffa$57a89080$06f9b180$@codeaurora.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hi,

>
>We expect arch_teardown_dma_ops() to be called very late in a device's
>life, after it has been removed from its bus, and thus after the IOMMU
>bus notifier has run. As such, even if this funny little check did make
>sense, it's unlikely to achieve what it thinks it's trying to do anyway.
>It's a residual trace of an earlier implementation which didn't belong
>here from the start; belatedly snuff it out.
>
>Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>---
> arch/arm64/mm/dma-mapping.c | 5 -----
> 1 file changed, 5 deletions(-)
>
>diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
>index 5cd0a383b14b..290a84f3351f 100644
>--- a/arch/arm64/mm/dma-mapping.c
>+++ b/arch/arm64/mm/dma-mapping.c
>@@ -940,11 +940,6 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
>
> void arch_teardown_dma_ops(struct device *dev)
> {
>-	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>-
>-	if (WARN_ON(domain))
>-		iommu_detach_device(domain, dev);
>-

Thanks!!, clears my doubt that i had for quite sometime.

Regards,
 Sricharan