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SubjectRe: [Nouveau] [PATCH v4 2/6] drm/nouveau: map pages using DMA API on platform devices
On Tue, Jul 08, 2014 at 05:25:57PM +0900, Alexandre Courbot wrote:
> page_to_phys() is not the correct way to obtain the DMA address of a
> buffer on a non-PCI system. Use the DMA API functions for this, which
> are portable and will allow us to use other DMA API functions for
> buffer synchronization.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> drivers/gpu/drm/nouveau/core/engine/device/base.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/core/engine/device/base.c b/drivers/gpu/drm/nouveau/core/engine/device/base.c
> index 18c8c7245b73..e4e9e64988fe 100644
> --- a/drivers/gpu/drm/nouveau/core/engine/device/base.c
> +++ b/drivers/gpu/drm/nouveau/core/engine/device/base.c
> @@ -489,7 +489,10 @@ nv_device_map_page(struct nouveau_device *device, struct page *page)
> if (pci_dma_mapping_error(device->pdev, ret))
> ret = 0;
> } else {
> - ret = page_to_phys(page);
> + ret = dma_map_page(&device->platformdev->dev, page, 0,
> + PAGE_SIZE, DMA_BIDIRECTIONAL);
> + if (dma_mapping_error(&device->platformdev->dev, ret))
> + ret = 0;
> }
>
> return ret;
> @@ -501,6 +504,9 @@ nv_device_unmap_page(struct nouveau_device *device, dma_addr_t addr)
> if (nv_device_is_pci(device))
> pci_unmap_page(device->pdev, addr, PAGE_SIZE,
> PCI_DMA_BIDIRECTIONAL);

pci_map/unmap alias to dma_unmap/map when called on the underlying struct
device embedded in pci_device (like for platform drivers). Dunno whether
it's worth to track a pointer to the struct device directly and always
call dma_unmap/map.

Just drive-by comment since I'm interested in how you solve this - i915
has similar fun with buffer sharing and coherent and non-coherent
platforms. Although we don't have fun with pci and non-pci based
platforms.
-Daniel

> + else
> + dma_unmap_page(&device->platformdev->dev, addr,
> + PAGE_SIZE, DMA_BIDIRECTIONAL);
> }
>
> int
> --
> 2.0.0
>
> _______________________________________________
> Nouveau mailing list
> Nouveau@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/nouveau

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch


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