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

[Marek Vasut]

On 07/26/2016 12:55 PM, Tien Fong Chee 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.

Can you elaborate on the issue in more depth ?
This patch looks like some sort of workaround/hack.

> 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(-)
> 
> 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
> 


-- 
Best regards,
Marek Vasut