Merge tag 'dmaengine-5.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine

Pull dmaengine updates from Vinod Koul:
 "A bunch of new support and few updates to drivers:

  New support:
   - DMA_MEMCPY_SG support is bought back as we have a user in Xilinx
     driver
   - Support for TI J721S2 SoC in k3-udma driver
   - Support for Ingenic MDMA and BDMA in the JZ4760
   - Support for Renesas r8a779f0 dmac

  Updates:
   - We are finally getting rid of slave_id, so this brings in the
     changes across tree for that
   - updates for idxd driver
   - at_xdmac driver cleanup"

* tag 'dmaengine-5.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vkoul/dmaengine: (60 commits)
  dt-bindings: dma-controller: Split interrupt fields in example
  dmaengine: pch_dma: Remove usage of the deprecated "pci-dma-compat.h" API
  dmaengine: at_xdmac: Fix race over irq_status
  dmaengine: at_xdmac: Remove a level of indentation in at_xdmac_tasklet()
  dmaengine: at_xdmac: Fix at_xdmac_lld struct definition
  dmaengine: at_xdmac: Fix lld view setting
  dmaengine: at_xdmac: Remove a level of indentation in at_xdmac_advance_work()
  dmaengine: at_xdmac: Fix concurrency over xfers_list
  dmaengine: at_xdmac: Move the free desc to the tail of the desc list
  dmaengine: at_xdmac: Fix race for the tx desc callback
  dmaengine: at_xdmac: Fix concurrency over chan's completed_cookie
  dmaengine: at_xdmac: Print debug message after realeasing the lock
  dmaengine: at_xdmac: Start transfer for cyclic channels in issue_pending
  dmaengine: at_xdmac: Don't start transactions at tx_submit level
  dmaengine: idxd: deprecate token sysfs attributes for read buffers
  dmaengine: idxd: change bandwidth token to read buffers
  dmaengine: idxd: fix wq settings post wq disable
  dmaengine: idxd: change MSIX allocation based on per wq activation
  dmaengine: idxd: fix descriptor flushing locking
  dmaengine: idxd: embed irq_entry in idxd_wq struct
  ...

1 files changed, 23 insertions, 0 deletions

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