mainlining shenanigans
4e4a105f1f
The RX descriptors of the PPv2 hardware allow to store several information, amongst which: - the DMA address of the buffer in which the data has been received - a "cookie" field, left to the use of the driver, and not used by the hardware In the current implementation, the "cookie" field is used to store the virtual address of the buffer, so that in the receive completion path, we can easily get the virtual address of the buffer that corresponds to a completed RX descriptors. On PPv2.1, used on 32-bit platforms, those two fields are 32-bit wide, which is enough to store a DMA address in the first field, and a virtual address in the second field. On PPv2.2, used on 64-bit platforms, these two fields have been extended to 40 bits. While 40 bits is enough to store a DMA address (as long as the DMA mask is 40 bits or lower), it is not enough to store a virtual address. Therefore, the "cookie" field can no longer be used to store the virtual address of the buffer. However, as Russell King pointed out, the RX buffers are always allocated in the kernel linear mapping, and therefore using phys_to_virt() on the physical address of the RX buffer is possible and correct. Therefore, this commit changes the driver to use the "cookie" field to store the physical address instead of the virtual address. phys_to_virt() is used in the receive completion path to retrieve the virtual address from the physical address. It is obviously important to realize that the DMA address and physical address are two different things, which is why we store both in the RX descriptors. While those addresses may be identical in some situations, it remains two distinct concepts, and both addresses should be handled separately. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.