Commit ef94b041 authored by Amelie Delaunay's avatar Amelie Delaunay Committed by Vinod Koul
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dt-bindings: dma: add alternative REQ/ACK protocol selection in stm32-dma 



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: default avatarAmelie Delaunay <amelie.delaunay@foss.st.com>
Acked-by: default avatarRob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210624093959.142265-2-amelie.delaunay@foss.st.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent af2eec75

Documentation/devicetree/bindings/dma/st,stm32-dma.yaml

+7 −0
Original line number Diff line number Diff line
@@ -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.





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