[PATCH v6 07/12] soc: aspeed: xdma: Add user interface
andrew at aj.id.au
Fri Jan 17 11:09:33 AEDT 2020
On Thu, 16 Jan 2020, at 07:59, Eddie James wrote:
> This commits adds a miscdevice to provide a user interface to the XDMA
> engine. The interface provides the write operation to start DMA
> operations. The DMA parameters are passed as the data to the write call.
> The actual data to transfer is NOT passed through write. Note that both
> directions of DMA operation are accomplished through the write command;
> BMC to host and host to BMC.
> The XDMA driver reserves an area of physical memory for DMA operations,
> as the XDMA engine is restricted to accessing certain physical memory
> areas on some platforms. This memory forms a pool from which users can
> allocate pages for their usage with calls to mmap. The space allocated
> by a client will be the space used in the DMA operation. For an
> "upstream" (BMC to host) operation, the data in the client's area will
> be transferred to the host. For a "downstream" (host to BMC) operation,
> the host data will be placed in the client's memory area.
> Poll is also provided in order to determine when the DMA operation is
> complete for non-blocking IO.
> Signed-off-by: Eddie James <eajames at linux.ibm.com>
Reviewed-by: Andrew Jeffery <andrew at aj.id.au>
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