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80327ce3d4
The host1x_bo_pin() and host1x_bo_unpin() APIs are used to pin and unpin buffers during host1x job submission. Pinning currently returns the SG table and the DMA address (an IOVA if an IOMMU is used or a physical address if no IOMMU is used) of the buffer. The DMA address is only used for buffers that are relocated, whereas the host1x driver will map gather buffers into its own IOVA space so that they can be processed by the CDMA engine. This approach has a couple of issues. On one hand it's not very useful to return a DMA address for the buffer if host1x doesn't need it. On the other hand, returning the SG table of the buffer is suboptimal because a single SG table cannot be shared for multiple mappings, because the DMA address is stored within the SG table, and the DMA address may be different for different devices. Subsequent patches will move the host1x driver over to the DMA API which doesn't work with a single shared SG table. Fix this by returning a new SG table each time a buffer is pinned. This allows the buffer to be referenced by multiple jobs for different engines. Change the prototypes of host1x_bo_pin() and host1x_bo_unpin() to take a struct device *, specifying the device for which the buffer should be pinned. This is required in order to be able to properly construct the SG table. While at it, make host1x_bo_pin() return the SG table because that allows us to return an ERR_PTR()-encoded error code if we need to, or return NULL to signal that we don't need the SG table to be remapped and can simply use the DMA address as-is. At the same time, returning the DMA address is made optional because in the example of command buffers, host1x doesn't need to know the DMA address since it will have to create its own mapping anyway. Signed-off-by: Thierry Reding <treding@nvidia.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.