linux-kernel - [PATCH V3 2/3] arm64: dts: qcom: sc7180: Add sleep pin ctrl for BT uart

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Date:   Thu, 20 Aug 2020 19:21:06 +0530
From:   satya priya <skakit@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Matthias Kaehlcke <mka@...omium.org>, gregkh@...uxfoundation.org,
        Andy Gross <agross@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, akashast@...eaurora.org,
        rojay@...eaurora.org, msavaliy@....qualcomm.com,
        satya priya <skakit@...eaurora.org>
Subject: [PATCH V3 2/3] arm64: dts: qcom: sc7180: Add sleep pin ctrl for BT uart

Add sleep pin ctrl for BT uart, and also change the bias
configuration to match Bluetooth module.

Signed-off-by: satya priya <skakit@...eaurora.org>
Reviewed-by: Akash Asthana <akashast@...eaurora.org>
---
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.

 arch/arm64/boot/dts/qcom/sc7180-idp.dts | 54 +++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc7180-idp.dts b/arch/arm64/boot/dts/qcom/sc7180-idp.dts
index d8b5507..806f626 100644
--- a/arch/arm64/boot/dts/qcom/sc7180-idp.dts
+++ b/arch/arm64/boot/dts/qcom/sc7180-idp.dts
@@ -473,20 +473,20 @@
 
 &qup_uart3_default {
 	pinconf-cts {
-		/*
-		 * Configure a pull-down on 38 (CTS) to match the pull of
-		 * the Bluetooth module.
-		 */
+		/* Configure no pull on 38 (CTS) to match Bluetooth module */
 		pins = "gpio38";
-		bias-pull-down;
-		output-high;
+		bias-disable;
 	};
 
 	pinconf-rts {
-		/* We'll drive 39 (RTS), so no pull */
+		/*
+		 * Configure pull-down on 39 (RTS). This is needed to avoid a
+		 * floating pin which could mislead Bluetooth controller
+		 * with UART RFR state (READY/NOT_READY).
+		 */
 		pins = "gpio39";
 		drive-strength = <2>;
-		bias-disable;
+		bias-pull-down;
 	};
 
 	pinconf-tx {
@@ -494,7 +494,43 @@
 		pins = "gpio40";
 		drive-strength = <2>;
 		bias-disable;
-		output-high;
+	};
+
+	pinconf-rx {
+		/*
+		 * Configure a pull-up on 41 (RX). This is needed to avoid
+		 * garbage data when the TX pin of the Bluetooth module is
+		 * in tri-state (module powered off or not driving the
+		 * signal yet).
+		 */
+		pins = "gpio41";
+		bias-pull-up;
+	};
+};
+
+&qup_uart3_sleep {
+	pinconf-cts {
+		/* Configure no-pull on 38 (CTS) to match Bluetooth module */
+		pins = "gpio38";
+		bias-disable;
+	};
+
+	pinconf-rts {
+		/*
+		 * Configure pull-down on 39 (RTS). This is needed to avoid a
+		 * floating pin which could mislead Bluetooth controller
+		 * with UART RFR state (READY/NOT_READY).
+		 */
+		pins = "gpio39";
+		drive-strength = <2>;
+		bias-pull-down;
+	};
+
+	pinconf-tx {
+		/* Configure pull-up on 40 (TX) when it isn't actively driven */
+		pins = "gpio40";
+		drive-strength = <2>;
+		bias-pull-up;
 	};
 
 	pinconf-rx {
-- 
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