[U-Boot] [PATCH] serial: Enable checking UART is ready for console based on device tree

[Simon Glass]

Hi,

On 26 July 2016 at 04:55, Tien Fong Chee <tfchee at altera.com> wrote:
> This patch would do checking on device tree to ensure the UART exist
> in the system and ready for console before setting have_console to true.
> This is required to avoid unexpected behavior such as hang during UART
> initialization.
>
> Signed-off-by: Tien Fong Chee <tfchee at altera.com>
> Cc: Dinh Nguyen <dinguyen at opensource.altera.com>
> Cc: Dinh Nguyen <dinh.linux at gmail.com>
> Cc: ChinLiang <clsee at altera.com>
> Cc: Thomas Chou <thomas at wytron.com.tw>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Marek Vasut <marex at denx.de>
> ---
>  common/console.c                  |   11 ++++---
>  common/spl/spl.c                  |    3 +-
>  drivers/serial/serial.c           |   58 +++++++++++++++++++++++++++++++++++-
>  include/asm-generic/global_data.h |    1 +
>  include/serial.h                  |    1 +
>  5 files changed, 66 insertions(+), 8 deletions(-)

Another way to deal with this would be to have the driver return
-EBUSY (or perhaps -EAGAIN) and set this flag in
serial_find_console_or_panic(). After all, the unavailability of
serial is a driver-specific thing, right?

How / when does the FPGA get programmed on your system?

>
> diff --git a/common/console.c b/common/console.c
> index 12293f3..c37486c 100644
> --- a/common/console.c
> +++ b/common/console.c
> @@ -690,14 +690,15 @@ int console_assign(int file, const char *devname)
>  /* Called before relocation - use serial functions */
>  int console_init_f(void)
>  {
> -       gd->have_console = 1;
> -
> +       if(gd->uart_ready_for_console) {
> +               gd->have_console = 1;
>  #ifdef CONFIG_SILENT_CONSOLE
> -       if (getenv("silent") != NULL)
> -               gd->flags |= GD_FLG_SILENT;
> +               if (getenv("silent") != NULL)
> +                       gd->flags |= GD_FLG_SILENT;
>  #endif
>
> -       print_pre_console_buffer(PRE_CONSOLE_FLUSHPOINT1_SERIAL);
> +               print_pre_console_buffer(PRE_CONSOLE_FLUSHPOINT1_SERIAL);
> +       }
>
>         return 0;
>  }
> diff --git a/common/spl/spl.c b/common/spl/spl.c
> index b7ec333..c18827d 100644
> --- a/common/spl/spl.c
> +++ b/common/spl/spl.c
> @@ -488,7 +488,8 @@ void preloader_console_init(void)
>
>         serial_init();          /* serial communications setup */
>
> -       gd->have_console = 1;
> +       if(gd->uart_ready_for_console)
> +               gd->have_console = 1;
>
>         puts("\nU-Boot SPL " PLAIN_VERSION " (" U_BOOT_DATE " - " \
>                         U_BOOT_TIME ")\n");
> diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
> index f1bd15b..95690e0 100644
> --- a/drivers/serial/serial.c
> +++ b/drivers/serial/serial.c
> @@ -35,6 +35,51 @@ static void serial_null(void)
>  }
>
>  /**
> + * uart_console_null() - This empty function would be used if UART console checking
> + *                       function is not compiled into U-boot.
> + *
> + * This routine returns true to indicate UART is ready for console by default.
> + * The driver is aliased to this empty function in case
> + * the driver is not compiled into U-Boot.
> + */
> +static int uart_console_null(void)
> +{
> +       return 1;
> +}
> +
> +/**
> + * uart_console_func() - Forward declare of driver checking UART is ready based
> + *                      on device tree.
> + * @name:      Name of driver which checking UART is ready based on device tree .
> + *
> + * This macro expands onto forward declaration of a driver checking
> + * UART is ready based on device tree, which allows own assigned function name.
> + * The declaration is made weak and aliases to uart_console_null() so in case
> + * the driver is not compiled in, the function is still declared and can
> + * be used, but aliases to uart_console_null() and thus is optimized away.
> + */
> +#define uart_console_func(name)                                        \
> +       int name(const void *blob)                                              \
> +               __attribute__((weak, alias("uart_console_null")));
> +
> +uart_console_func(is_default_uart_console_true);
> +
> +/**
> + * is_uart_console_true() - Common function to abstract the specific UART
> + *                         console checking function.
> + *
> + * This is common interface for specific UART console checking function.
> + */
> +int is_uart_console_true(const void *blob)
> +{
> +       int ret = 0;
> +
> +       ret |= is_default_uart_console_true(blob);
> +
> +       return ret;
> +}
> +
> +/**
>   * on_baudrate() - Update the actual baudrate when the env var changes
>   *
>   * This will check for a valid baudrate and only apply it if valid.
> @@ -415,8 +460,17 @@ static struct serial_device *get_current(void)
>   */
>  int serial_init(void)
>  {
> -       gd->flags |= GD_FLG_SERIAL_READY;
> -       return get_current()->start();
> +       if(is_uart_console_true(gd->fdt_blob))
> +               gd->uart_ready_for_console = 1;
> +       else
> +               gd->uart_ready_for_console = 0;
> +
> +       if(gd->uart_ready_for_console) {
> +               gd->flags |= GD_FLG_SERIAL_READY;
> +               return get_current()->start();
> +       }
> +
> +       return 0;
>  }
>
>  /**
> diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
> index a6d1d2a..1cb7ef7 100644
> --- a/include/asm-generic/global_data.h
> +++ b/include/asm-generic/global_data.h
> @@ -44,6 +44,7 @@ typedef struct global_data {
>  #ifdef CONFIG_BOARD_TYPES
>         unsigned long board_type;
>  #endif
> +       unsigned long uart_ready_for_console; /* UART ready to support console */
>         unsigned long have_console;     /* serial_init() was called */
>  #ifdef CONFIG_PRE_CONSOLE_BUFFER
>         unsigned long precon_buf_idx;   /* Pre-Console buffer index */
> diff --git a/include/serial.h b/include/serial.h
> index 47332c5..a95bf70 100644
> --- a/include/serial.h
> +++ b/include/serial.h
> @@ -50,6 +50,7 @@ extern void serial_initialize(void);
>  extern void serial_stdio_init(void);
>  extern int serial_assign(const char *name);
>  extern void serial_reinit_all(void);
> +extern int is_uart_console_true(const void *blob);
>
>  /* For usbtty */
>  #ifdef CONFIG_USB_TTY
> --
> 1.7.7.4
>

Regards,
Simon