[PATCH] cmd: go: Flush cache before jumping to app/image

[Daniel Schwierzeck]

On Wed, Feb 12, 2020 at 1:21 PM Stefan Roese <sr at denx.de> wrote:
>
> It has been noticed on MT7628/88 platforms, that booting the RAM image
> does not work reliably. Sometimes it works and sometimes not. Debugging
> showed that this "might" be a cache related issue as very strange
> errors occured (output corrupted etc).
>
> This patch adds a cache flush for the complete SDRAM area to the go cmd
> before jumping to the entry point. The complete area is flushed as we
> don't know at this point, how big the area of the "application" really
> is.
>
> Signed-off-by: Stefan Roese <sr at denx.de>
> Cc: Daniel Schwierzeck <daniel.schwierzeck at gmail.com>
> Cc: Mauro Condarelli <mc5686 at mclink.it>
> Cc: Weijie Gao <weijie.gao at mediatek.com>
> ---
>  cmd/boot.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/cmd/boot.c b/cmd/boot.c
> index 9150fce80b..968522face 100644
> --- a/cmd/boot.c
> +++ b/cmd/boot.c
> @@ -9,10 +9,13 @@
>   */
>  #include <common.h>
>  #include <command.h>
> +#include <cpu_func.h>
>  #include <net.h>
>
>  #ifdef CONFIG_CMD_GO
>
> +DECLARE_GLOBAL_DATA_PTR;
> +
>  /* Allow ports to override the default behavior */
>  __attribute__((weak))
>  unsigned long do_go_exec(ulong (*entry)(int, char * const []), int argc,
> @@ -33,6 +36,13 @@ static int do_go(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
>
>         printf ("## Starting application at 0x%08lX ...\n", addr);
>
> +       /*
> +        * Flush cache before jumping to application. Let's flush the
> +        * whole SDRAM area, since we don't know the size of the image
> +        * that was loaded.
> +        */
> +       flush_cache(gd->bd->bi_memstart, gd->bd->bi_memsize);
> +
>         /*
>          * pass address parameter as argv[0] (aka command name),
>          * and all remaining args
> --
> 2.25.0
>

I think that's not right for all architectures or cache-coherent
systems. It would be better
to implement do_go_exec() in arch/mips/libs/bootm.c because this function is
already annotated as weak.

-- 
- Daniel