UART controllers without flow control seem to behave unstable in case DMA is enabled. The issues were indicated in the message: https://lore.kernel.org/linux-arm-kernel/CAMdYzYpXtMocCtCpZLU_xuWmOp2Ja_v0Aj... In case of PX30-uQ7 Ringneck SoM, it was noticed that after couple of hours of UART communication, the CPU stall was occurring, leading to the system becoming unresponsive. After disabling the DMA, extensive UART communication tests for up to two weeks were performed, and no issues were further observed. The flow control pins for uart5 are not available on PX30-uQ7 Ringneck, as configured by pinctrl-0, so the DMA nodes were removed on SoM dtsi.
Cc: stable@vger.kernel.org Fixes: c484cf93f61b ("arm64: dts: rockchip: add PX30-µQ7 (Ringneck) SoM with Haikou baseboard") Reviewed-by: Quentin Schulz quentin.schulz@cherry.de Signed-off-by: Lukasz Czechowski lukasz.czechowski@thaumatec.com --- arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi index 2c87005c89bd3..e80412abec081 100644 --- a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi +++ b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi @@ -397,6 +397,8 @@ &u2phy_host { };
&uart5 { + /delete-property/ dmas; + /delete-property/ dma-names; pinctrl-0 = <&uart5_xfer>; };