Performance oriented customized Linux kernel based on the mainline kernel.
bd96f1b2f4
Modify dw_edma_device_transfer() to also support the semantics of dma device transfer for additional use cases involving pcitest utility as a local initiator. For its original use case, dw-edma supported the semantics of dma device transfer from the perspective of a remote initiator who is located across the PCIe bus from dma channel hardware. To a remote initiator, DMA_DEV_TO_MEM means using a remote dma WRITE channel to transfer from remote memory to local memory. A WRITE channel would be employed on the remote device in order to move the contents of remote memory to the bus destined for local memory. To a remote initiator, DMA_MEM_TO_DEV means using a remote dma READ channel to transfer from local memory to remote memory. A READ channel would be employed on the remote device in order to move the contents of local memory to the bus destined for remote memory. >From the perspective of a local dma initiator who is co-located on the same side of the PCIe bus as the dma channel hardware, the semantics of dma device transfer are flipped. To a local initiator, DMA_DEV_TO_MEM means using a local dma READ channel to transfer from remote memory to local memory. A READ channel would be employed on the local device in order to move the contents of remote memory to the bus destined for local memory. To a local initiator, DMA_MEM_TO_DEV means using a local dma WRITE channel to transfer from local memory to remote memory. A WRITE channel would be employed on the local device in order to move the contents of local memory to the bus destined for remote memory. To support local dma initiators, dw_edma_device_transfer() is modified to now examine the direction field of struct dma_slave_config for the channel which initiators can configure by calling dmaengine_slave_config(). If direction is configured as either DMA_DEV_TO_MEM or DMA_MEM_TO_DEV, local initiator semantics are used. If direction is a value other than DMA_DEV_TO_MEM nor DMA_MEM_TO_DEV, then remote initiator semantics are used. This should maintain backward compatibility with the original use case of dw-edma. The dw-edma-test utility is an example of a remote initiator. From reading its patch, dw-edma-test does not specifically set the direction field of struct dma_slave_config. Since dw_edma_device_transfer() also does not check the direction field of struct dma_slave_config, it seems safe to use this convention in dw-edma to support both local and remote initiator semantics. Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com> Link: https://lore.kernel.org/r/1588122633-1552-1-git-send-email-alan.mikhak@sifive.com Signed-off-by: Vinod Koul <vkoul@kernel.org> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.