arm64: dts: rockchip: Disable DMA for uart5 on px30-ringneck

commit 5ae4dca718eacd0a56173a687a3736eb7e627c77 upstream.

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_v0Aj0e6YFNRA-yV7u14g@mail.gmail.com/
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>
Link: https://lore.kernel.org/r/20250121125604.3115235-3-lukasz.czechowski@thaumatec.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
[ conflict resolution due to missing (cosmetic) backport of
  4eee627ea59304cdd66c5d4194ef13486a6c44fc]
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
index 5fcc5f32be2d79cb62faca4c2d72baab5726d0f0..2963d634baba99f9f7216904b0a6b542c71d78ba 100644 (file)
--- a/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
+++ b/arch/arm64/boot/dts/rockchip/px30-ringneck.dtsi
@@ -367,6 +367,11 @@
        status = "okay";
 };
 
+&uart5 {
+       /delete-property/ dmas;
+       /delete-property/ dma-names;
+};
+
 /* Mule UCAN */
 &usb_host0_ehci {
        status = "okay";