Re: [PATCH] ARM: dts: samsung: exynos4210-i9100: Fix Bluetooth node

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Baud rate mismatch between Bluetooth controller and host UART due to driver clamping.
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commit cb253c8ef9aaafc70357be54516beee25ad6e5a6
Author: Paul Cercueil <paul@crapouillou.net>

ARM: dts: samsung: exynos4210-i9100: Fix Bluetooth node

This commit adds the uart-has-rtscts property to the bluetooth node and
configures the max-speed property to 4000000 (4 Mbps) to fix choppy audio
issues on the Galaxy S2.

> diff --git a/arch/arm/boot/dts/samsung/exynos4210-i9100.dts b/arch/arm/boot/dts/samsung/exynos4210-i9100.dts
> --- a/arch/arm/boot/dts/samsung/exynos4210-i9100.dts
> +++ b/arch/arm/boot/dts/samsung/exynos4210-i9100.dts
> @@ -875,11 +875,14 @@ &serial_0 {
>  	status = "okay";
>  
>  	pinctrl-names = "default";
> +	uart-has-rtscts;
>  	pinctrl-0 = <&bt_en>, <&bt_res>, <&uart0_data>, <&uart0_fctl>;
>  
>  	bluetooth {
>  		compatible = "brcm,bcm4330-bt";
>  
> +		max-speed = <4000000>;

[Severity: High]
Does this configuration cause a baud rate mismatch between the Bluetooth
controller and the host UART?

When bcm_setup() configures the Broadcom controller to 4,000,000 bps, it then
calls host_set_baudrate() to configure the host Exynos UART to match.

However, the request propagates to the Exynos UART driver in
drivers/tty/serial/samsung_tty.c, which enforces a hardcoded maximum baud rate
of 3,000,000 via s3c24xx_serial_set_termios():

    baud = uart_get_baud_rate(port, termios, old, 0, 3000000);

Because 4,000,000 exceeds this limit, uart_get_baud_rate() falls back to max - 1,
returning 2,999,999.

This creates a baud rate mismatch that introduces framing errors and breaks
subsequent HCI communication.

> +
>  		shutdown-gpios = <&gpl0 4 GPIO_ACTIVE_HIGH>;
>  		reset-gpios = <&gpl1 0 GPIO_ACTIVE_LOW>;
>  		device-wakeup-gpios = <&gpx3 1 GPIO_ACTIVE_HIGH>;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260828184331.655804-1-paul@crapouillou.net?part=1