[PATCH] arm64: dts: qcom: msm8998: Fixup uart3 gpio config for bluetooth

[PATCH] arm64: dts: qcom: msm8998: Fixup uart3 gpio config for bluetooth

[Jeffrey Hugo]

It turns out that the wcn3990 can float the gpio lines during bootup, etc
which will result in the uart core thinking there is incoming data.  This
results in the bluetooth stack getting garbage.  By applying a bias to
match what wcn3990 would drive, the issue is corrected.

Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
---
 .../boot/dts/qcom/msm8998-clamshell.dtsi      | 31 +++++++++++++++++++
 arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi     | 31 +++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi b/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
index ab24d415acc0..7e02cb6c8e07 100644
--- a/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
@@ -74,6 +74,37 @@
 	};
 };
 
+&blsp1_uart3_on {
+	/delete-node/ config;
+
+	pinconf-cts {
+		/*
+		 * Configure a pull-down on 47 (CTS) to match the pull
+		 * of the Bluetooth module.
+		 */
+		pins = "gpio47";
+		bias-pull-down;
+	};
+
+	pinconf-rts-tx {
+		/* We'll drive 48 (RFR) and 45 (TX), so no pull */
+		pins = "gpio45", "gpio48";
+		drive-strength = <2>;
+		bias-disable;
+	};
+
+	pinconf-rx {
+		/*
+		 * Configure a pull-up on 45 (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 = "gpio45";
+		bias-pull-up;
+	};
+};
+
 &dsi0 {
 	status = "okay";
 
diff --git a/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi b/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
index 1a1836ed1052..17f51af5e999 100644
--- a/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
@@ -37,6 +37,37 @@
 	};
 };
 
+&blsp1_uart3_on {
+	/delete-node/ config;
+
+	pinconf-cts {
+		/*
+		 * Configure a pull-down on 47 (CTS) to match the pull
+		 * of the Bluetooth module.
+		 */
+		pins = "gpio47";
+		bias-pull-down;
+	};
+
+	pinconf-rts-tx {
+		/* We'll drive 48 (RFR) and 45 (TX), so no pull */
+		pins = "gpio45", "gpio48";
+		drive-strength = <2>;
+		bias-disable;
+	};
+
+	pinconf-rx {
+		/*
+		 * Configure a pull-up on 45 (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 = "gpio45";
+		bias-pull-up;
+	};
+};
+
 &blsp2_uart1 {
 	status = "okay";
 };
-- 
2.17.1

Re: [PATCH] arm64: dts: qcom: msm8998: Fixup uart3 gpio config for bluetooth

[Bjorn Andersson]

On Sat 19 Oct 15:12 PDT 2019, Jeffrey Hugo wrote:

> It turns out that the wcn3990 can float the gpio lines during bootup, etc
> which will result in the uart core thinking there is incoming data.  This
> results in the bluetooth stack getting garbage.  By applying a bias to
> match what wcn3990 would drive, the issue is corrected.
> 
> Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
> ---
>  .../boot/dts/qcom/msm8998-clamshell.dtsi      | 31 +++++++++++++++++++
>  arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi     | 31 +++++++++++++++++++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi b/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
> index ab24d415acc0..7e02cb6c8e07 100644
> --- a/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
> +++ b/arch/arm64/boot/dts/qcom/msm8998-clamshell.dtsi
> @@ -74,6 +74,37 @@
>  	};
>  };
>  
> +&blsp1_uart3_on {
> +	/delete-node/ config;

So it would make much more sense then to split &blsp1_uart3_on in
sections defining its pins, than the "logical" config and mux split.


Please send a patch that changes msm8998-pins.dtsi to be:

blsp_uart3_on: blsp1-uart3-on {
	ctx {
	};

	rts {
	};

	rx [
	};

	tx {
	};
};


There's no need for the "pinconf" part and for pinctrl states with a
single pin/group we can simply omit the subnode (as this is now
possible).


Apart from that, I think this looks good!

Regards,
Bjorn

> +
> +	pinconf-cts {
> +		/*
> +		 * Configure a pull-down on 47 (CTS) to match the pull
> +		 * of the Bluetooth module.
> +		 */
> +		pins = "gpio47";
> +		bias-pull-down;
> +	};
> +
> +	pinconf-rts-tx {
> +		/* We'll drive 48 (RFR) and 45 (TX), so no pull */
> +		pins = "gpio45", "gpio48";
> +		drive-strength = <2>;
> +		bias-disable;
> +	};
> +
> +	pinconf-rx {
> +		/*
> +		 * Configure a pull-up on 45 (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 = "gpio45";
> +		bias-pull-up;
> +	};
> +};
> +
>  &dsi0 {
>  	status = "okay";
>  
> diff --git a/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi b/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
> index 1a1836ed1052..17f51af5e999 100644
> --- a/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
> +++ b/arch/arm64/boot/dts/qcom/msm8998-mtp.dtsi
> @@ -37,6 +37,37 @@
>  	};
>  };
>  
> +&blsp1_uart3_on {
> +	/delete-node/ config;
> +
> +	pinconf-cts {
> +		/*
> +		 * Configure a pull-down on 47 (CTS) to match the pull
> +		 * of the Bluetooth module.
> +		 */
> +		pins = "gpio47";
> +		bias-pull-down;
> +	};
> +
> +	pinconf-rts-tx {
> +		/* We'll drive 48 (RFR) and 45 (TX), so no pull */
> +		pins = "gpio45", "gpio48";
> +		drive-strength = <2>;
> +		bias-disable;
> +	};
> +
> +	pinconf-rx {
> +		/*
> +		 * Configure a pull-up on 45 (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 = "gpio45";
> +		bias-pull-up;
> +	};
> +};
> +
>  &blsp2_uart1 {
>  	status = "okay";
>  };
> -- 
> 2.17.1
>