[U-Boot] [PATCH 02/14] arm: Optionally use existing atags in bootm.c

[Marek Vasut <marek.vasut@gmail.com>]

> This patch adapts the bootm command so that it can use an existing atags
> command set up by a previous bootloader.

Why do you need it?

> If the environment variable
> "atagaddr" is unset, bootm behaves as normal. If "atagaddr" is set, bootm
> will use atags address from environment variable and also append new boot
> args (if specified in u-boot). For example, if a previous boot loader
> already set up the atags struct at 0x80000100:
> 
> setenv atagaddr 0x80000100; bootm 0x80008000

Can't you set those atags correctly in uboot?

M
> 
> Signed-off-by: Pali Roh?r <pali.rohar@gmail.com>
> ---
> Changes since original version:
>    - Added info to README file
>    - Added local define CONFIG_SETUP_ANY_TAG
>    - Fixed compile warning
>    - Fixed commit message
>    - Check if atagaddr is not NULL
> 
>  README               |    2 ++
>  arch/arm/lib/bootm.c |   39 ++++++++++++++++++++++++++++++++-------
>  2 files changed, 34 insertions(+), 7 deletions(-)
> 
> diff --git a/README b/README
> index 9d713e8..8c3b98a 100644
> --- a/README
> +++ b/README
> @@ -3584,6 +3584,8 @@ Some configuration options can be set using
> Environment Variables.
> 
>  List of environment variables (most likely not complete):
> 
> +  atagaddr	- bootm will use ATAGs struct from specified address (arm only)
> +
>    baudrate	- see CONFIG_BAUDRATE
> 
>    bootdelay	- see CONFIG_BOOTDELAY
> diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
> index afa0093..8366dd5 100644
> --- a/arch/arm/lib/bootm.c
> +++ b/arch/arm/lib/bootm.c
> @@ -93,6 +93,14 @@ static void announce_and_cleanup(void)
>  	cleanup_before_linux();
>  }
> 
> +#if defined(CONFIG_SETUP_MEMORY_TAGS) || \
> +defined(CONFIG_CMDLINE_TAG) || \
> +defined(CONFIG_INITRD_TAG) || \
> +defined(CONFIG_SERIAL_TAG) || \
> +defined(CONFIG_REVISION_TAG)
> +#define CONFIG_SETUP_ANY_TAG
> +#endif
> +
>  int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t
> *images) {
>  	bd_t	*bd = gd->bd;
> @@ -125,12 +133,22 @@ int do_bootm_linux(int flag, int argc, char *argv[],
> bootm_headers_t *images) debug ("## Transferring control to Linux (at
> address %08lx) ...\n", (ulong) kernel_entry);
> 
> -#if defined (CONFIG_SETUP_MEMORY_TAGS) || \
> -    defined (CONFIG_CMDLINE_TAG) || \
> -    defined (CONFIG_INITRD_TAG) || \
> -    defined (CONFIG_SERIAL_TAG) || \
> -    defined (CONFIG_REVISION_TAG)
> -	setup_start_tag (bd);
> +	s = getenv("atagaddr");
> +	if (s)
> +		bd->bi_boot_params = simple_strtoul(s, NULL, 16);
> +
> +	if (bd->bi_boot_params) {
> +		printf("Using existing atags at %#lx\n", bd->bi_boot_params);
> +
> +		params = (struct tag *) bd->bi_boot_params;
> +		while (params->hdr.size > 0)
> +			params = tag_next(params);
> +	} else {
> +#ifdef CONFIG_SETUP_ANY_TAG
> +		setup_start_tag(bd);
> +#endif
> +	}
> +
>  #ifdef CONFIG_SERIAL_TAG
>  	setup_serial_tag (&params);
>  #endif
> @@ -147,8 +165,15 @@ int do_bootm_linux(int flag, int argc, char *argv[],
> bootm_headers_t *images) if (images->rd_start && images->rd_end)
>  		setup_initrd_tag (bd, images->rd_start, images->rd_end);
>  #endif
> -	setup_end_tag(bd);
> +
> +	if (s) {
> +		if (params->hdr.size > 0)
> +			setup_end_tag(bd);
> +	} else {
> +#ifdef CONFIG_SETUP_ANY_TAG
> +		setup_end_tag(bd);
>  #endif
> +	}
> 
>  	announce_and_cleanup();