[U-Boot] [PATCH 2/2] sunxi: Enable pre-console buffer

[Ian Campbell]

On Thu, 2015-01-08 at 09:02 +0200, Siarhei Siamashka wrote:
> This allows to always have a complete log on the VGA/HDMI/LCD console.
> 
> Signed-off-by: Siarhei Siamashka <siarhei.siamashka at gmail.com>
> ---
>  include/configs/sunxi-common.h | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
> index b4324ee..5ddcc42 100644
> --- a/include/configs/sunxi-common.h
> +++ b/include/configs/sunxi-common.h
> @@ -272,10 +272,15 @@
>  #ifndef CONFIG_SPL_BUILD
>  #include <config_distro_defaults.h>
>  
> +/* Enable pre-console buffer to get complete log on the VGA console */
> +#define CONFIG_PRE_CONSOLE_BUFFER
> +#define CONFIG_PRE_CON_BUF_SZ		(1024 * 1024)
> +#define CONFIG_PRE_CON_BUF_ADDR		(0x43000000 - CONFIG_PRE_CON_BUF_SZ)
> +
>  /*
>   * 240M RAM (256M minimum minus space for the framebuffer),
> - * 32M uncompressed kernel, 16M compressed kernel, 1M fdt,
> - * 1M script, 1M pxe and the ramdisk at the end.
> + * 32M uncompressed kernel, 15M compressed kernel, 1M pre-console
> + * buffer, 1M fdt, 1M script, 1M pxe and the ramdisk at the end.

Am I correct in thinking that the pre-console buffer is long gone
(replaced by the actual console) by the time any of these mem layout
choices come into play (i.e. long before anything might load a kernel,
initrd or fdt)?

If yes then I think it is confusing to modify this comment, and the
comment before the pre-console #defines should mention that the buffer
is boottime only/short lived etc.

If no then I'm not sure putting a "u-boot managed" buffer in the middle
of the "user managed" load space is a good idea, since it could lead to
odd/hard to debug corruptions etc if the kernel was >15M.

Either way I think it would be better to put this buffer somewhere else
entirely since it isn't really the same as these things.

>   */
>  #define MEM_LAYOUT_ENV_SETTINGS \
>  	"bootm_size=0xf000000\0" \

Both u-boot-sunxi#master and #next still have 0x10000000 here, which
tree is this patch on? Some branch of Hans' tree (with "sunxi:
sunxi-common.h: Reduce bootm_size to take the framebuffer into account"
in it) I suppose?

Perhaps a better place for the pre-console buffer would be right before
the framebuffer (or at the top of RAM if no video on the board), with
modifications to bootm_size or not depending on the answer to the
original question above.

Ian.