[PATCH v4 07/39] serial: msm: add debug UART

[Sumit Garg]

On Fri, 16 Feb 2024 at 02:22, Caleb Connolly <caleb.connolly at linaro.org> wrote:
>
> Introduce support for early debugging. This relies on the previous stage
> bootloader to initialise the UART clocks, when running with U-Boot as
> the primary bootloader this feature doesn't work. It will require a way
> to configure the clocks before the driver model is available.
>
> Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
> ---
>  drivers/serial/Kconfig      |  8 ++++++++
>  drivers/serial/serial_msm.c | 37 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 45 insertions(+)
>
> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> index 26460c4e0cab..fbd351a47859 100644
> --- a/drivers/serial/Kconfig
> +++ b/drivers/serial/Kconfig
> @@ -319,6 +319,14 @@ config DEBUG_UART_S5P
>           will need to provide parameters to make this work. The driver will
>           be available until the real driver-model serial is running.
>
> +config DEBUG_UART_MSM
> +       bool "Qualcomm QUP UART debug"
> +       depends on ARCH_SNAPDRAGON

Since this debug UART only works for chainloaded configuration, can we
somehow add explicit dependency here? Something like !REMAKE_ELF?

-Sumit

> +       help
> +         Select this to enable a debug UART using the serial_msm driver. You
> +         will need to provide parameters to make this work. The driver will
> +         be available until the real driver-model serial is running.
> +
>  config DEBUG_UART_MSM_GENI
>         bool "Qualcomm snapdragon"
>         depends on ARCH_SNAPDRAGON
> diff --git a/drivers/serial/serial_msm.c b/drivers/serial/serial_msm.c
> index f4d96313b931..44b93bd7ff21 100644
> --- a/drivers/serial/serial_msm.c
> +++ b/drivers/serial/serial_msm.c
> @@ -252,3 +252,40 @@ U_BOOT_DRIVER(serial_msm) = {
>         .probe = msm_serial_probe,
>         .ops    = &msm_serial_ops,
>  };
> +
> +#ifdef CONFIG_DEBUG_UART_MSM
> +
> +static struct msm_serial_data init_serial_data = {
> +       .base = CONFIG_VAL(DEBUG_UART_BASE),
> +       .clk_rate = 7372800,
> +};
> +
> +#include <debug_uart.h>
> +
> +/* Uncomment to turn on UART clocks when debugging U-Boot as aboot on MSM8916 */
> +//int apq8016_clk_init_uart(phys_addr_t gcc_base);
> +
> +static inline void _debug_uart_init(void)
> +{
> +       /* Uncomment to turn on UART clocks when debugging U-Boot as aboot on MSM8916 */
> +       //apq8016_clk_init_uart(0x1800000);
> +       uart_dm_init(&init_serial_data);
> +}
> +
> +static inline void _debug_uart_putc(int ch)
> +{
> +       struct msm_serial_data *priv = &init_serial_data;
> +
> +       while (!(readl(priv->base + UARTDM_SR) & UARTDM_SR_TX_EMPTY) &&
> +              !(readl(priv->base + UARTDM_ISR) & UARTDM_ISR_TX_READY))
> +               ;
> +
> +       writel(UARTDM_CR_CMD_RESET_TX_READY, priv->base + UARTDM_CR);
> +
> +       writel(1, priv->base + UARTDM_NCF_TX);
> +       writel(ch, priv->base + UARTDM_TF);
> +}
> +
> +DEBUG_UART_FUNCS
> +
> +#endif
>
> --
> 2.43.1
>