linux-kernel - [PATCH v2] dts: Disable DMA support on the BK4 vf610 device's fsl

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Date:   Thu, 10 Oct 2019 11:08:02 +0200
From:   Lukasz Majewski <lukma@...x.de>
To:     linux-kernel@...r.kernel.org, Shawn Guo <shawnguo@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Stefan Agner <stefan@...er.ch>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Lukasz Majewski <lukma@...x.de>,
        Robin Murphy <robin.murphy@....com>
Subject: [PATCH v2] dts: Disable DMA support on the BK4 vf610 device's fsl_lpuart driver

This change disables the DMA support (RX/TX) on the NXP's fsl_lpuart
driver - the PIO mode is used instead. This change is necessary for better
robustness of BK4's device use cases with many potentially interrupted
short serial transfers.

Without it the driver hangs when some distortion happens on UART lines.

Signed-off-by: Lukasz Majewski <lukma@...x.de>
Suggested-by: Robin Murphy <robin.murphy@....com>

---
Changes for v2:
- Use /delete-property/dma-names; instead of dma-names = "","";
---
 arch/arm/boot/dts/vf610-bk4.dts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/boot/dts/vf610-bk4.dts b/arch/arm/boot/dts/vf610-bk4.dts
index 0f3870d3b099..830c85476b3d 100644
--- a/arch/arm/boot/dts/vf610-bk4.dts
+++ b/arch/arm/boot/dts/vf610-bk4.dts
@@ -259,24 +259,28 @@
 &uart0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart0>;
+	/delete-property/dma-names;
 	status = "okay";
 };
 
 &uart1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart1>;
+	/delete-property/dma-names;
 	status = "okay";
 };
 
 &uart2 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart2>;
+	/delete-property/dma-names;
 	status = "okay";
 };
 
 &uart3 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart3>;
+	/delete-property/dma-names;
 	status = "okay";
 };
 
-- 
2.20.1