[PATCH V6 2/4] arm64: dts: qcom: sc7180: Add wakeup support for BT UART on sc7180-idp

[satya priya]

Add the necessary pinctrl, interrupt property and a suitable sleep config
to support Bluetooth wakeup feature.

GPIO mode is configured in sleep state to drive the RTS/RFR line low.
If QUP function is selected in sleep state, UART RTS/RFR is pulled high
during suspend and BT SoC not able to send wakeup bytes.

Signed-off-by: satya priya <skakit@xxxxxxxxxxxxxx>
---
Changes in V2:
 - This patch adds sleep state for BT UART. Newly added in V2.

Changes in V3:
 - Remove "output-high" for TX from both sleep and default states
   as it is not required. Configure pull-up for TX in sleep state.

Changes in V4:
 - As per Matthias's comment, removed drive-strength for sleep state
   and fixed nit-pick.

Changes in V5:
 - As per Matthias's comments, moved pinmux change for sleep state,
   pinctrl and interrupt config to the board specific file.

Changes in V6:
 - As per Doug's comments changed subject, deleted interrupts property.
 - As per Bjorn's comments changed commit text and rationale for RTS,
   TX and RX.

 arch/arm64/boot/dts/qcom/sc7180-idp.dts | 55 +++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sc7180-idp.dts b/arch/arm64/boot/dts/qcom/sc7180-idp.dts
index 04888df..e416409 100644
--- a/arch/arm64/boot/dts/qcom/sc7180-idp.dts
+++ b/arch/arm64/boot/dts/qcom/sc7180-idp.dts
@@ -346,6 +346,13 @@
 &uart3 {
 	status = "okay";
 
+	/delete-property/interrupts;
+	interrupts-extended = <&intc GIC_SPI 604 IRQ_TYPE_LEVEL_HIGH>,
+				<&tlmm 41 IRQ_TYPE_EDGE_FALLING>;
+
+	pinctrl-names = "default", "sleep";
+	pinctrl-1 = <&qup_uart3_sleep>;
+
 	bluetooth: wcn3990-bt {
 		compatible = "qcom,wcn3990-bt";
 		vddio-supply = <&vreg_l10a_1p8>;
@@ -545,3 +552,51 @@
 	};
 };
 
+&tlmm {
+	qup_uart3_sleep: qup-uart3-sleep {
+		pinmux {
+			pins = "gpio38", "gpio39",
+			       "gpio40", "gpio41";
+			function = "gpio";
+		};
+
+		pinconf-cts {
+			/*
+			 * Configure a pull-down on CTS to match the pull of
+			 * the Bluetooth module.
+			 */
+			pins = "gpio38";
+			bias-pull-down;
+		};
+
+		pinconf-rts {
+			/*
+			 * Configure pull-down on RTS. As RTS is active low
+			 * signal, pull it low to indicate the BT SoC that it
+			 * can wakeup the system anytime from suspend state by
+			 * pulling RX low (by sending wakeup bytes).
+			 */
+			 pins = "gpio39";
+			 bias-pull-down;
+		};
+
+		pinconf-tx {
+			/*
+			 * Configure pull-up on TX when it isn't actively driven
+			 * to prevent BT SoC from receiving garbage during sleep.
+			 */
+			pins = "gpio40";
+			bias-pull-up;
+		};
+
+		pinconf-rx {
+			/*
+			 * Configure a pull-up on RX. This is needed to avoid
+			 * garbage data when the TX pin of the Bluetooth module
+			 * is floating which may cause spurious wakeups.
+			 */
+			pins = "gpio41";
+			bias-pull-up;
+		};
+	};
+};
-- 
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