From: Christoph Hellwig <hch@lst.de>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: "Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
"Pawel Osciak" <pawel@osciak.com>,
"Russell King" <linux@armlinux.org.uk>,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
"Kyungmin Park" <kyungmin.park@samsung.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
linuxppc-dev@lists.ozlabs.org, "Christoph Hellwig" <hch@lst.de>,
linux-arm-kernel@lists.infradead.org,
linux-media@vger.kernel.org
Subject: Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource
Date: Thu, 17 Jan 2019 18:21:52 +0100 [thread overview]
Message-ID: <20190117172152.GA32292@lst.de> (raw)
In-Reply-To: <6f8892ac-c2aa-10df-c74f-ba032bf75160@samsung.com>
On Mon, Jan 14, 2019 at 01:42:26PM +0100, Marek Szyprowski wrote:
> Hi Christoph,
>
> On 2019-01-11 19:17, Christoph Hellwig wrote:
> > vb2_dc_get_userptr pokes into arm direct mapping details to get the
> > resemblance of a dma address for a a physical address that does is
> > not backed by a page struct. Not only is this not portable to other
> > architectures with dma direct mapping offsets, but also not to uses
> > of IOMMUs of any kind. Switch to the proper dma_map_resource /
> > dma_unmap_resource interface instead.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> There are checks for IOMMU presence in other places in vb2-dma-contig,
> so it was used only when no IOMMU is available, but I agree that the
> hacky code should be replaced by a generic code if possible.
>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>
> V4L2 pipeline works fine on older Exynos-based boards with CMA and IOMMU
> disabled.
Do you know if these rely on the offsets? E.g. would they still work
with the patch below applied on top. That would keep the map_resource
semantics as-is as solve the issue pointed out by Robin for now.
If not I can only think of a flag to bypass the offseting for now, but
that would be pretty ugly. Or go for the long-term solution of
discovering the relationship between the two devices, as done by the
PCIe P2P code..
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 8e0359b04957..25bd19974223 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -359,7 +359,7 @@ EXPORT_SYMBOL(dma_direct_map_sg);
dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- dma_addr_t dma_addr = phys_to_dma(dev, paddr);
+ dma_addr_t dma_addr = paddr;
if (unlikely(!dma_direct_possible(dev, dma_addr, size))) {
report_addr(dev, dma_addr, size);
next prev parent reply other threads:[~2019-01-17 17:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190111181841epcas3p2d7c0bf8f5c11a9863e22ec1b12da6e1b@epcas3p2.samsung.com>
2019-01-11 18:17 ` fix a layering violation in videobuf2 and improve dma_map_resource Christoph Hellwig
2019-01-11 18:17 ` [PATCH 1/3] dma-mapping: remove the default map_resource implementation Christoph Hellwig
2019-01-14 13:12 ` Robin Murphy
2019-01-14 17:08 ` Christoph Hellwig
2019-01-11 18:17 ` [PATCH 2/3] dma-mapping: don't BUG when calling dma_map_resource on RAM Christoph Hellwig
2019-01-14 14:16 ` Robin Murphy
2019-01-11 18:17 ` [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource Christoph Hellwig
2019-01-11 19:54 ` Mauro Carvalho Chehab
2019-01-14 10:31 ` Christoph Hellwig
2019-01-14 11:04 ` Mauro Carvalho Chehab
2019-01-14 11:12 ` Christoph Hellwig
2019-01-14 12:42 ` Marek Szyprowski
2019-01-17 17:21 ` Christoph Hellwig [this message]
2019-01-18 9:41 ` Marek Szyprowski
2019-01-31 15:31 ` Christoph Hellwig
2019-01-14 11:43 ` fix a layering violation in videobuf2 and improve dma_map_resource Marek Szyprowski
2019-01-18 11:37 fix a layering violation in videobuf2 and improve dma_map_resource v2 Christoph Hellwig
2019-01-18 11:37 ` [PATCH 3/3] videobuf2: replace a layering violation with dma_map_resource Christoph Hellwig
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