[PATCH 1/2] dt-bindings: dma: add alternative REQ/ACK protocol selection in stm32-dma
From: Amelie Delaunay <amelie.delaunay@foss.st.com>
Date: 2021-06-24 09:40:28
Also in:
dmaengine, linux-devicetree, lkml
Subsystem:
dma generic offload engine subsystem, open firmware and flattened device tree bindings, the rest · Maintainers:
Vinod Koul, Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds
Default REQ/ACK protocol consists in maintaining ACK signal up to the removal of REQuest and the transfer completion. In case of alternative REQ/ACK protocol, ACK de-assertion does not wait the removal of the REQuest, but only the transfer completion. Due to a possible DMA stream lock when transferring data to/from STM32 USART/UART, this new bindings allow to select this alternative protocol in device tree, especially for STM32 USART/UART nodes. Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com> --- Documentation/devicetree/bindings/dma/st,stm32-dma.yaml | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/Documentation/devicetree/bindings/dma/st,stm32-dma.yaml b/Documentation/devicetree/bindings/dma/st,stm32-dma.yaml
index 2a5325f480f6..4bf676fd25dc 100644
--- a/Documentation/devicetree/bindings/dma/st,stm32-dma.yaml
+++ b/Documentation/devicetree/bindings/dma/st,stm32-dma.yaml@@ -40,6 +40,13 @@ description: | 0x0: FIFO mode with threshold selectable with bit 0-1 0x1: Direct mode: each DMA request immediately initiates a transfer from/to the memory, FIFO is bypassed. + -bit 4: alternative DMA request/acknowledge protocol + 0x0: Use standard DMA ACK management, where ACK signal is maintained + up to the removal of request and transfer completion + 0x1: Use alternative DMA ACK management, where ACK de-assertion does + not wait for the de-assertion of the REQuest, ACK is only managed + by transfer completion. This must only be used on channels + managing transfers for STM32 USART/UART. maintainers:
--
2.25.1
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