From: Amelie Delaunay <amelie.delaunay@foss.st.com>
To: Vinod Koul <vkoul@kernel.org>, Rob Herring <robh+dt@kernel.org>,
Dan Williams <dan.j.williams@intel.com>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: <dmaengine@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-stm32@st-md-mailman.stormreply.com>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>,
Amelie Delaunay <amelie.delaunay@foss.st.com>,
Pierre-Yves Mordret <pierre-yves.mordret@foss.st.com>
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 [thread overview]
Message-ID: <20210624093959.142265-2-amelie.delaunay@foss.st.com> (raw)
In-Reply-To: <20210624093959.142265-1-amelie.delaunay@foss.st.com>
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
next prev parent reply other threads:[~2021-06-24 9:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-24 9:39 [PATCH 0/2] STM32 DMA alternative REQ/ACK protocol support Amelie Delaunay
2021-06-24 9:39 ` Amelie Delaunay [this message]
2021-07-14 19:27 ` [PATCH 1/2] dt-bindings: dma: add alternative REQ/ACK protocol selection in stm32-dma Rob Herring
2021-06-24 9:39 ` [PATCH 2/2] dmaengine: stm32-dma: add alternate REQ/ACK protocol management Amelie Delaunay
2021-07-28 7:09 ` [PATCH 0/2] STM32 DMA alternative REQ/ACK protocol support Vinod Koul
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