From: Tomasz Figa <tfiga@google.com>
To: shunqian.zheng@gmail.com
Cc: "Shunqian Zheng" <zhengsq@rock-chips.com>,
"Mark Rutland" <mark.rutland@arm.com>,
devicetree@vger.kernel.org, "Heiko Stübner" <heiko@sntech.de>,
"David Airlie" <airlied@linux.ie>,
"Joerg Roedel" <joro@8bytes.org>,
linux@armlinux.org.uk,
dri-devel <dri-devel@lists.freedesktop.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
"open list:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Rob Herring <robh+dt@kernel.org>, simon xue <xxm@rock-chips.com>,
linux-arm-kernel@lists.infradead.org" <mark.yao@rock-chips.com>
Subject: Re: [PATCH v2 6/7] iommu/rockchip: use DMA API to map, to flush cache
Date: Mon, 13 Jun 2016 19:21:26 +0900 [thread overview]
Message-ID: <CAAFQd5DDCd8VcdEhEASAK7NMBnVJWuUxgGURtsa2KQBKsgsxUQ@mail.gmail.com> (raw)
In-Reply-To: <575E834C.30305@gmail.com>
On Mon, Jun 13, 2016 at 6:56 PM, Shunqian Zheng
<shunqian.zheng@gmail.com> wrote:
> Hi
>
> On 2016年06月10日 17:10, Tomasz Figa wrote:
>>
>> Hi,
>>
>> On Wed, Jun 8, 2016 at 10:26 PM, Shunqian Zheng <zhengsq@rock-chips.com>
>> wrote:
>>>
>>> Use DMA API instead of architecture internal functions like
>>> __cpuc_flush_dcache_area() etc.
>>>
>>> To support the virtual device like DRM the virtual slave iommu
>>> added in the previous patch, attaching to which the DRM can use
>>> it own domain->dev for dma_map_*(), dma_sync_*() even VOP is disabled.
>>>
>>> With this patch, this driver is available for ARM64 like RK3399.
>>>
>> Could we instead simply allocate coherent memory for page tables using
>> dma_alloc_coherent() and skip any flushing on CPU side completely? If
>> I'm looking correctly, the driver only reads back the page directory
>> when checking if there is a need to allocate new page table, so there
>> shouldn't be any significant penalty for disabling the cache.
>
> I try to use dma_alloc_coherent() to replace the dma_map_single(),
> but it doesn't work for me properly.
> Because the DRM uses the iommu_dma_ops instead the swiotlb_dma_ops after
> attaching
> to iommu, so when the iommu domain need to alloc a new page in
> rk_iommu_map(),
> it would call:
> rk_iommu_map() --> dma_alloc_coherent() --> ops->alloc() --> iommu_map()
> --> rk_iommu_map()
It shouldn't call iommu_map(), because the IOMMU is not behind another
IOMMU. Are you sure you called dma_alloc_coherent() on behalf of the
IOMMU struct device and not the DRM device?
Best regards,
Tomasz
next prev parent reply other threads:[~2016-06-13 10:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-08 13:26 [PATCH v2 0/7] fix bugs; enable iommu for ARM64 Shunqian Zheng
2016-06-08 13:26 ` [PATCH v2 1/7] iommu/rockchip: fix devm_{request,free}_irq parameter Shunqian Zheng
2016-06-10 5:30 ` Tomasz Figa
2016-06-08 13:26 ` [PATCH v2 2/7] iommu/rockchip: add map_sg callback for rk_iommu_ops Shunqian Zheng
2016-06-10 5:31 ` Tomasz Figa
2016-06-08 13:26 ` [PATCH v2 3/7] iommu/rockchip: support virtual iommu slave device Shunqian Zheng
2016-06-10 6:22 ` Tomasz Figa
2016-06-08 13:26 ` [PATCH v2 4/7] ARM: dts: rockchip: add virtual iommu for display Shunqian Zheng
2016-06-10 6:22 ` Tomasz Figa
2016-06-08 13:26 ` [PATCH v2 5/7] drm: rockchip: use common iommu api to attach iommu Shunqian Zheng
2016-06-10 8:03 ` Tomasz Figa
2016-06-08 13:26 ` [PATCH v2 6/7] iommu/rockchip: use DMA API to map, to flush cache Shunqian Zheng
2016-06-10 9:10 ` Tomasz Figa
[not found] ` <575E834C.30305@gmail.com>
2016-06-13 10:21 ` Tomasz Figa [this message]
[not found] ` <575E8B6F.1040103@gmail.com>
2016-06-13 10:41 ` Tomasz Figa
2016-06-13 10:39 ` Robin Murphy
2016-06-08 13:26 ` [PATCH v2 7/7] iommu/rockchip: enable rockchip iommu on ARM64 platform Shunqian Zheng
2016-06-10 9:12 ` Tomasz Figa
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