| Message ID | 20210624093959.142265-2-amelie.delaunay@foss.st.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | STM32 DMA alternative REQ/ACK protocol support | expand |
On Thu, 24 Jun 2021 11:39:58 +0200, Amelie Delaunay wrote: > 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(+) > Acked-by: Rob Herring <robh@kernel.org>
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:
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(+)