Re: [PATCH u-boot-marvell 1/2] arm: mvebu: spl: Add option to reset the board on DDR training failure

["Marek Behún" <kabel@kernel.org>]

On Thu, 17 Feb 2022 12:37:54 +0100
Pali Rohár <pali@kernel.org> wrote:

> On Thursday 17 February 2022 01:08:48 Marek Behún wrote:
> > From: Marek Behún <marek.behun@nic.cz>
> > 
> > Some boards may occacionally fail DDR training. Currently we hang() in
> > this case. Add an option that makes the board do an immediate reset in
> > such a case, so that a new training is tried as soon as possible,
> > instead of hanging and possibly waiting for watchdog to reset the board.
> > 
> > Signed-off-by: Marek Behún <marek.behun@nic.cz>
> > Reviewed-by: Stefan Roese <sr@denx.de>
> > ---
> >  arch/arm/mach-mvebu/Kconfig | 9 +++++++++
> >  arch/arm/mach-mvebu/spl.c   | 6 +++++-
> >  2 files changed, 14 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm/mach-mvebu/Kconfig b/arch/arm/mach-mvebu/Kconfig
> > index d23cc0c760..ed957be6e1 100644
> > --- a/arch/arm/mach-mvebu/Kconfig
> > +++ b/arch/arm/mach-mvebu/Kconfig
> > @@ -213,6 +213,15 @@ config DDR_LOG_LEVEL
> >  	  At level 3, rovides the windows margin of each DQ as a results of
> >  	  DQS centeralization.
> >  
> > +config DDR_RESET_ON_TRAINING_FAILURE
> > +	bool "Reset the board on DDR training failure instead of hanging"
> > +	depends on ARMADA_38X || ARMADA_XP
> > +	help
> > +	  If DDR training fails in SPL, reset the board instead of hanging.
> > +	  Some boards are known to fail DDR training occasionally and an
> > +	  immediate reset may be preferable to waiting until the board is
> > +	  reset by watchdog (if there even is one).
> > +
> >  config SYS_BOARD
> >  	default "clearfog" if TARGET_CLEARFOG
> >  	default "helios4" if TARGET_HELIOS4
> > diff --git a/arch/arm/mach-mvebu/spl.c b/arch/arm/mach-mvebu/spl.c
> > index 273ecb8bd6..d3c3bdc74d 100644
> > --- a/arch/arm/mach-mvebu/spl.c
> > +++ b/arch/arm/mach-mvebu/spl.c
> > @@ -4,6 +4,7 @@
> >   */
> >  
> >  #include <common.h>
> > +#include <cpu_func.h>
> >  #include <dm.h>
> >  #include <fdtdec.h>
> >  #include <hang.h>
> > @@ -330,7 +331,10 @@ void board_init_f(ulong dummy)
> >  	ret = ddr3_init();
> >  	if (ret) {
> >  		printf("ddr3_init() failed: %d\n", ret);
> > -		hang();
> > +		if (IS_ENABLED(CONFIG_DDR_RESET_ON_TRAINING_FAILURE))
> > +			reset_cpu();  
> 
> You should not call reset_cpu() from SPL loaded via UART. This will
> confuse x-modem software. Either return failure to BootROM or hang()
> like it was before.

Hmm, I didn't consider that.

What will happen if I return failure to BootROM? Will it try booting
from different medium?

I think that the best thing to do on failure when booting via UART is
to hang()...

Marek