linux-kernel - [PATCH 01/16] ARM: dts: stm32: add DMA configuration to UART nodes on stm32mp151

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Date:   Thu, 3 Feb 2022 18:10:59 +0100
From:   Erwan Le Ray <erwan.leray@...s.st.com>
To:     Alexandre Torgue <alexandre.torgue@...s.st.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Erwan Le Ray <erwan.leray@...s.st.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Marek Vasut <marex@...x.de>,
        Marcin Sloniewski <marcin.sloniewski@...il.com>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        Jagan Teki <jagan@...rulasolutions.com>,
        <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 01/16] ARM: dts: stm32: add DMA configuration to UART nodes on stm32mp151

Add DMA configuration in stm32mp15x uart nodes by selecting dma direct
mode and alternate REQ/ACK dma protocol for uart.

DMA direct mode allows to bypass DMA FIFO. Each DMA request immediately
initiates a transfer from/to the memory. This allows USART to get data
transferred, even when the transfer ends before the DMA FIFO completion.

Default REQ/ACK DMA 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, select this alternative protocol in STM32 USART/UART nodes.

Signed-off-by: Valentin Caron <valentin.caron@...s.st.com>
Signed-off-by: Erwan Le Ray <erwan.leray@...s.st.com>

diff --git a/arch/arm/boot/dts/stm32mp151.dtsi b/arch/arm/boot/dts/stm32mp151.dtsi
index 1cfc2f011e70..e86006ae137b 100644
--- a/arch/arm/boot/dts/stm32mp151.dtsi
+++ b/arch/arm/boot/dts/stm32mp151.dtsi
@@ -455,6 +455,9 @@
 			interrupts-extended = <&exti 27 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc USART2_K>;
 			wakeup-source;
+			dmas = <&dmamux1 43 0x400 0x15>,
+			       <&dmamux1 44 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -464,6 +467,9 @@
 			interrupts-extended = <&exti 28 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc USART3_K>;
 			wakeup-source;
+			dmas = <&dmamux1 45 0x400 0x15>,
+			       <&dmamux1 46 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -473,6 +479,9 @@
 			interrupts-extended = <&exti 30 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc UART4_K>;
 			wakeup-source;
+			dmas = <&dmamux1 63 0x400 0x15>,
+			       <&dmamux1 64 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -482,6 +491,9 @@
 			interrupts-extended = <&exti 31 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc UART5_K>;
 			wakeup-source;
+			dmas = <&dmamux1 65 0x400 0x15>,
+			       <&dmamux1 66 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -588,6 +600,9 @@
 			interrupts-extended = <&exti 32 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc UART7_K>;
 			wakeup-source;
+			dmas = <&dmamux1 79 0x400 0x15>,
+			       <&dmamux1 80 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -597,6 +612,9 @@
 			interrupts-extended = <&exti 33 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc UART8_K>;
 			wakeup-source;
+			dmas = <&dmamux1 81 0x400 0x15>,
+			       <&dmamux1 82 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
@@ -678,6 +696,9 @@
 			interrupts-extended = <&exti 29 IRQ_TYPE_LEVEL_HIGH>;
 			clocks = <&rcc USART6_K>;
 			wakeup-source;
+			dmas = <&dmamux1 71 0x400 0x15>,
+			       <&dmamux1 72 0x400 0x11>;
+			dma-names = "rx", "tx";
 			status = "disabled";
 		};
 
-- 
2.17.1