On 20/09/2021 14:36, Bruce Richardson wrote:
On Fri, Sep 17, 2021 at 03:42:22PM +0000, Conor Walsh wrote:
Add data path functions for enqueuing and submitting operations to
IOAT devices.
Signed-off-by: Conor Walsh <conor.wa...@intel.com>
Reviewed-by: Kevin Laatz <kevin.la...@intel.com>
---
doc/guides/dmadevs/ioat.rst | 54 ++++++++++++++++++++
drivers/dma/ioat/ioat_dmadev.c | 92 ++++++++++++++++++++++++++++++++++
2 files changed, 146 insertions(+)
diff --git a/doc/guides/dmadevs/ioat.rst b/doc/guides/dmadevs/ioat.rst
index a64d67bf89..2464207e20 100644
--- a/doc/guides/dmadevs/ioat.rst
+++ b/doc/guides/dmadevs/ioat.rst
@@ -89,3 +89,57 @@ The following code shows how the device is configured in
``test_dmadev.c``:
Once configured, the device can then be made ready for use by calling the
``rte_dma_start()`` API.
+
+Performing Data Copies
+~~~~~~~~~~~~~~~~~~~~~~~
+
+To perform data copies using IOAT dmadev devices, the functions
+``rte_dma_copy()`` and ``rte_dma_submit()`` should be used. Alternatively
+``rte_dma_copy()`` can be called with the ``RTE_DMA_OP_FLAG_SUBMIT`` flag
+set.
+
+The ``rte_dma_copy()`` function enqueues a single copy to the
+device ring for copying at a later point. The parameters to the function
+include the device ID of the desired device, the virtual DMA channel required
+(always 0 for IOAT), the IOVA addresses of both the source and destination
+buffers, the length of the data to be copied and any operation flags. The
+function will return the index of the enqueued job which can be use to
+track that operation.
+
+While the ``rte_dma_copy()`` function enqueues a copy operation on the device
+ring, the copy will not actually be performed until after the application calls
+the ``rte_dma_submit()`` function. This function informs the device hardware
+of the elements enqueued on the ring, and the device will begin to process
them.
+It is expected that, for efficiency reasons, a burst of operations will be
+enqueued to the device via multiple enqueue calls between calls to the
+``rte_dma_submit()`` function. If desired you can pass the
+``RTE_DMA_OP_FLAG_SUBMIT`` flag when calling ``rte_dma_copy()`` and this will
+tell the device to perform the enqueued operation and any unperformed
operations
+before it. The ``RTE_DMA_OP_FLAG_SUBMIT`` flag can be passed instead of calling
+the ``rte_dma_submit()`` function for example on the last enqueue of the burst.
+
+The following code from demonstrates how to enqueue a burst of copies to the
+device and start the hardware processing of them:
+
+.. code-block:: C
+
+ for (i = 0; i < BURST_SIZE; i++) {
+ if (rte_dma_copy(dev_id, vchan, rte_mbuf_data_iova(srcs[i]),
+ rte_mbuf_data_iova(dsts[i]), COPY_LEN, 0) < 0) {
+ PRINT_ERR("Error with rte_dma_copy for buffer %u\n", i);
+ return -1;
+ }
+ }
+ if (rte_dma_submit(dev_id, vchan) < 0) {
+ PRINT_ERR("Error with performing operations\n", i);
+ return -1;
+ }
+
+Filling an Area of Memory
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The driver also has support for the ``fill`` operation, where an area
+of memory is overwritten, or filled, with a short pattern of data.
+Fill operations can be performed in much the same was as copy operations
+described above, just using the ``rte_dma_fill()`` function rather
+than the ``rte_dma_copy()`` function.
Similar to the feedback on the idxd driver, I think we need to see how much
of this text is already present in the generic dmadev documentation and
re-use or reference that. If it's not present, then these patches should
add it to the common doc, not a separate driver-specific doc.
/Bruce
I will work with Kevin to rewrite these to reduce the amount of
duplication between our drivers and for future drivers in the next version.
Thanks,
Conor.
