[U-Boot] xyz-modem: Change getc timeout loop waiting

[Alexander Sverdlin <alexander.sverdlin@gmail.com>]

Hello!

On Mon, 21 Nov 2016 10:18:51 +0200
Tomas Melin <tomas.melin@vaisala.com> wrote:

> This fixes the loop delay when using a hw watchdog.
> 
> In case a watchdog is used that accesses CPU registers,
> the defined delay of 20us in a tight loop will cause a
> huge delay in the actual timeout seen. This is caused
> by the fact that udelay will inheritantly call WATCHDOG_RESET.
> Together with the omap wdt implementation, the seen timeout increases up to
> around 30s. This makes the loop very slow and causes long
> delays when using the modem.
> 
> Instead, implement the 2 sec loop by using the timer interface to know
> when to break out of the timeout loop. Watchdog kicking is taken care of
> by getc().
> 
> Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>

This commit breaks YMODEM SPL->U-Boot boot on Beagle Bone,
transfer is aborted (because of timeout) after 497kb
(u-boot.img is around 570kb).
Reverting the commit repairs YMODEM boot.

> ---
>  common/xyzModem.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/common/xyzModem.c b/common/xyzModem.c
> index 5656aac..e0d87db 100644
> --- a/common/xyzModem.c
> +++ b/common/xyzModem.c
> @@ -71,12 +71,12 @@ typedef int cyg_int32;
>  static int
>  CYGACC_COMM_IF_GETC_TIMEOUT (char chan, char *c)
>  {
> -#define DELAY 20
> -  unsigned long counter = 0;
> -  while (!tstc () && (counter < xyzModem_CHAR_TIMEOUT * 1000 / DELAY))
> +
> +  ulong now = get_timer(0);
> +  while (!tstc ())
>      {
> -      udelay (DELAY);
> -      counter++;
> +      if (get_timer(now) > xyzModem_CHAR_TIMEOUT)
> +        break;
>      }
>    if (tstc ())
>      {


-- 
Alexander Sverdlin.