[U-Boot] [PATCH] SPL: tiny-printf: avoid any BSS usage

[Vignesh R <vigneshr@ti.com>]

On Monday 04 July 2016 05:26 AM, Andre Przywara wrote:
> As printf calls may be executed quite early, we should avoid using any
> BSS stored variables, since some boards put BSS in DRAM, which may not
> have been initialised yet.
> Explicitly mark those "static global" variables as belonging to the
> .data section, to keep tiny-printf clear of any BSS usage.
> Please note that this is quite a hack (which may need to be extended to
> other source files) and more sustainable solutions are warmly welcomed.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---

There is atleast one place where I encountered same issue:
drivers/i2c/i2c-uclass-compact.c:
static int cur_busnum;

I could verify that the below macro helps in that case as well.


> 
>  lib/tiny-printf.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/tiny-printf.c b/lib/tiny-printf.c
> index 451f4f7..bc2995b 100644
> --- a/lib/tiny-printf.c
> +++ b/lib/tiny-printf.c
> @@ -13,11 +13,18 @@
>  #include <stdarg.h>
>  #include <serial.h>
>  
> -static char *bf;
> -static char zs;
> +/*
> + * This code in here may execute before the DRAM is initialised, so
> + * we should make sure that it doesn't touch BSS, which some boards
> + * put in DRAM.
> + */
> +#define NO_BSS __attribute__((section(".data")))
> +
> +static char *bf NO_BSS;
> +static char zs NO_BSS;
>  
>  /* Current position in sprintf() output string */
> -static char *outstr;
> +static char *outstr NO_BSS;
>  
>  static void out(char c)
>  {
> 

-- 
Regards
Vignesh