diff options
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/dmaengine/dmatest.rst | 17 | ||||
| -rw-r--r-- | Documentation/driver-api/dmaengine/provider.rst | 23 |
2 files changed, 37 insertions, 3 deletions
diff --git a/Documentation/driver-api/dmaengine/dmatest.rst b/Documentation/driver-api/dmaengine/dmatest.rst index ee268d445d38..cf9859cd0b43 100644 --- a/Documentation/driver-api/dmaengine/dmatest.rst +++ b/Documentation/driver-api/dmaengine/dmatest.rst @@ -6,6 +6,16 @@ Andy Shevchenko <andriy.shevchenko@linux.intel.com> This small document introduces how to test DMA drivers using dmatest module. +The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using +various lengths and various offsets into the source and destination buffers. It +will initialize both buffers with a repeatable pattern and verify that the DMA +engine copies the requested region and nothing more. It will also verify that +the bytes aren't swapped around, and that the source buffer isn't modified. + +The dmatest module can be configured to test a specific channel. It can also +test multiple channels at the same time, and it can start multiple threads +competing for the same channel. + .. note:: The test suite works only on the channels that have at least one capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET @@ -143,13 +153,14 @@ Part 5 - Handling channel allocation Allocating Channels ------------------- -Channels are required to be configured prior to starting the test run. -Attempting to run the test without configuring the channels will fail. +Channels do not need to be configured prior to starting a test run. Attempting +to run the test without configuring the channels will result in testing any +channels that are available. Example:: % echo 1 > /sys/module/dmatest/parameters/run - dmatest: Could not start test, no channels configured + dmatest: No channels configured, continue with any Channels are registered using the "channel" parameter. Channels can be requested by their name, once requested, the channel is registered and a pending thread is added to the test list. diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst index ddb0a81a796c..0072c9c7efd3 100644 --- a/Documentation/driver-api/dmaengine/provider.rst +++ b/Documentation/driver-api/dmaengine/provider.rst @@ -162,6 +162,29 @@ Currently, the types available are: - The device is able to do memory to memory copies +- - DMA_MEMCPY_SG + + - The device supports memory to memory scatter-gather transfers. + + - Even though a plain memcpy can look like a particular case of a + scatter-gather transfer, with a single chunk to copy, it's a distinct + transaction type in the mem2mem transfer case. This is because some very + simple devices might be able to do contiguous single-chunk memory copies, + but have no support for more complex SG transfers. + + - No matter what the overall size of the combined chunks for source and + destination is, only as many bytes as the smallest of the two will be + transmitted. That means the number and size of the scatter-gather buffers in + both lists need not be the same, and that the operation functionally is + equivalent to a ``strncpy`` where the ``count`` argument equals the smallest + total size of the two scatter-gather list buffers. + + - It's usually used for copying pixel data between host memory and + memory-mapped GPU device memory, such as found on modern PCI video graphics + cards. The most immediate example is the OpenGL API function + ``glReadPielx()``, which might require a verbatim copy of a huge framebuffer + from local device memory onto host memory. + - DMA_XOR - The device is able to perform XOR operations on memory areas |