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Thu, 24 Jun 2021 11:40:04 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 0A58810002A; Thu, 24 Jun 2021 11:40:04 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id E7F1D21B51B; Thu, 24 Jun 2021 11:40:03 +0200 (CEST) Received: from localhost (10.75.127.47) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 24 Jun 2021 11:40:03 +0200 From: Amelie Delaunay To: Vinod Koul , Rob Herring , Dan Williams , Maxime Coquelin , Alexandre Torgue CC: , , , , , Amelie Delaunay , Pierre-Yves Mordret Subject: [PATCH 1/2] dt-bindings: dma: add alternative REQ/ACK protocol selection in stm32-dma Date: Thu, 24 Jun 2021 11:39:58 +0200 Message-ID: <20210624093959.142265-2-amelie.delaunay@foss.st.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210624093959.142265-1-amelie.delaunay@foss.st.com> References: <20210624093959.142265-1-amelie.delaunay@foss.st.com> MIME-Version: 1.0 X-Originating-IP: [10.75.127.47] X-ClientProxiedBy: SFHDAG1NODE3.st.com (10.75.127.3) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-06-24_06:2021-06-24, 2021-06-24 signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210624_024018_425624_79C3195C X-CRM114-Status: GOOD ( 13.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 --- 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: