[PATCH v2] mach-snapdragon: formalize APQ8016 debug UART init

[Stephan Gerhold]

On Wed, Jun 10, 2026 at 11:57:20AM +1000, Sam Day via B4 Relay wrote:
> From: Sam Day <me at samcday.com>
> 
> The dragonboard410c (and likely other SB-off devices) can run U-Boot
> early enough in the boot chain such that UART clock isn't started, and
> pins aren't configured.
> 
> APQ8016 has two UART peripherals, each with its own clock and TLMM pins.
> 
> Two new debug-apq8016-uartN.config fragments are provided. Each
> configures the appropriate UARTDM aperture. The newly introduced
> DEBUG_UART_APQ8016 Kconfig symbol pulls in MSM debug UART, and enables a
> board-level debug_uart_init function to start the right clock and mux
> the right TX pin.
> 
> Signed-off-by: Sam Day <me at samcday.com>
> ---
> Changes in v2:
> - Rename APQ8016_TLMM_GPIO_ENABLE to APQ8016_TLMM_GPIO_OE
> - Link to v1: https://lore.kernel.org/r/20260603-apq8016-debug-uart-v1-1-1e46b2cd0fe6@samcday.com
> ---
>  arch/arm/mach-snapdragon/Kconfig              |  9 +++++++
>  arch/arm/mach-snapdragon/Makefile             |  1 +
>  arch/arm/mach-snapdragon/debug-uart-apq8016.c | 37 +++++++++++++++++++++++++++
>  board/qualcomm/debug-apq8016-uart1.config     |  4 +++
>  board/qualcomm/debug-apq8016-uart2.config     |  4 +++
>  drivers/serial/Kconfig                        |  1 +
>  drivers/serial/serial_msm.c                   | 10 --------
>  7 files changed, 56 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/mach-snapdragon/Kconfig b/arch/arm/mach-snapdragon/Kconfig
> index d3de8693b5a..43e6fd1bc42 100644
> --- a/arch/arm/mach-snapdragon/Kconfig
> +++ b/arch/arm/mach-snapdragon/Kconfig
> @@ -1,5 +1,14 @@
>  if ARCH_SNAPDRAGON
>  
> +config DEBUG_UART_APQ8016
> +	bool "APQ8016 early debug initialization"
> +	select CLK_QCOM_APQ8016
> +	select CONFIG_DEBUG_UART_MSM

Should we have the CONFIG_ prefix here in Kconfig? Not sure if both
works, but I'd expect this isn't required/typical here.

Thanks,
Stephan