From ef94b0413bf4e0d328989fecf5b773e82c8794ac Mon Sep 17 00:00:00 2001 From: Amelie Delaunay Date: Thu, 24 Jun 2021 11:39:58 +0200 Subject: 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: Amelie Delaunay Acked-by: Rob Herring Link: https://lore.kernel.org/r/20210624093959.142265-2-amelie.delaunay@foss.st.com Signed-off-by: Vinod Koul --- Documentation/devicetree/bindings/dma/st,stm32-dma.yaml | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Documentation/devicetree/bindings/dma') 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: -- cgit v1.2.3