ARM: tegra: Fix Tegra30 Cardhu PCA954x reset

On all versions of Tegra30 Cardhu, the reset signal to the NXP PCA9546 I2C mux is connected to the Tegra GPIO BB0. Currently, this pin on the Tegra is not configured as a GPIO but as a special-function IO (SFIO) that is multiplexing the pin to an I2S controller. On exiting system suspend, I2C commands sent to the PCA9546 are failing because there is no ACK. Although it is not possible to see exactly what is happening to the reset during suspend, by ensuring it is configured as a GPIO and driven high, to de-assert the reset, the failures are no longer seen.

Please note that this GPIO is also used to drive the reset signal going to the camera connector on the board. However, given that there is no camera support currently for Cardhu, this should not have any impact.

---
 arch/arm/boot/dts/tegra30-cardhu.dtsi | 1 +
 1 file changed, 1 insertion(+)

index 92a9740c533f..3b1db7b9ec50 100644
@@ -206,6 +206,7 @@
 			#address-cells = <1>;
 			#size-cells = <0>;
 			reg = <0x70>;
+			reset-gpio = <&gpio TEGRA_GPIO(BB, 0) GPIO_ACTIVE_LOW>;
 		};
 	};
 

1.9.1

Applied to for-4.19/arm/dt, thanks.

Thierry
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