linux-kernel - [V6 1/2] arm64: dts: qcom: sc7280-idp: Configure CTS pin to bias-bus-hold for bluetooth

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Date:   Thu, 21 Apr 2022 21:26:06 +0530
From:   Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To:     agross@...nel.org, bjorn.andersson@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     quic_msavaliy@...cinc.com, dianders@...omium.org,
        Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
Subject: [V6 1/2] arm64: dts: qcom: sc7280-idp: Configure CTS pin to bias-bus-hold for bluetooth

WLAN rail was leaking power during RBSC/sleep even after turning BT off.
Change active and sleep pinctrl configurations to handle same.

Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
---
v6: add code comments about how bias-bus-hold could save power
v5: modify subject to include bluetooth
v4: modify subject of patch to indicate file it is applying to
v3: apply same change to active state and other sc7280*.dts* as well
v2: used bias-bus-hold as per review comments
v1: intial patch used bias-disable for sleep pinctrl in sc7280-idp only
---
 arch/arm64/boot/dts/qcom/sc7280-idp.dtsi | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
index 015a347..6c2aab6 100644
--- a/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
+++ b/arch/arm64/boot/dts/qcom/sc7280-idp.dtsi
@@ -400,10 +400,13 @@
 
 &qup_uart7_cts {
 	/*
-	 * Configure a pull-down on CTS to match the pull of
-	 * the Bluetooth module.
+	 * Configure a bias-bus-hold on CTS to lower power
+	 * usage when Bluetooth is turned off. Bus hold will
+	 * maintain a low power state regardless of whether
+	 * the Bluetooth module drives the pin in either
+	 * direction or leaves the pin fully unpowered.
 	 */
-	bias-pull-down;
+	bias-bus-hold;
 };
 
 &qup_uart7_rts {
@@ -495,10 +498,13 @@
 		pins = "gpio28";
 		function = "gpio";
 		/*
-		 * Configure a pull-down on CTS to match the pull of
-		 * the Bluetooth module.
+		 * Configure a bias-bus-hold on CTS to lower power
+		 * usage when Bluetooth is turned off. Bus hold will
+		 * maintain a low power state regardless of whether
+		 * the Bluetooth module drives the pin in either
+		 * direction or leaves the pin fully unpowered.
 		 */
-		bias-pull-down;
+		bias-bus-hold;
 	};
 
 	qup_uart7_sleep_rts: qup-uart7-sleep-rts {
-- 
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