[U-Boot] [PATCH] arm: socfpga: dm: Fix DM initialization failure after warm reset

[Marek Vasut <marex@denx.de>]

On Saturday, August 29, 2015 at 04:49:37 PM, Simon Glass wrote:
> Hi Marek,
> 
> On 29 August 2015 at 08:46, Marek Vasut <marex@denx.de> wrote:
> > On Saturday, August 29, 2015 at 04:39:43 PM, Simon Glass wrote:
> >> Hi Marek,
> >> 
> >> On 29 August 2015 at 01:56, Marek Vasut <marex@denx.de> wrote:
> >> > On Saturday, August 29, 2015 at 01:21:31 AM, Simon Glass wrote:
> >> > > Hi,
> >> > > 
> >> > > On 28 August 2015 at 02:41, Jian Luo <Jian.Luo4@boschrexroth.de> wrote:
> >> > > > gd->dm_root is not cleared in SPL after warm reset.
> >> > > > This might cause DM initilazation failure.
> >> > > > 
> >> > > > Signed-off-by: Jian Luo <jian.luo4@boschrexroth.de>
> >> > > > ---
> >> > > > 
> >> > > >  arch/arm/mach-socfpga/spl.c | 6 ++++++
> >> > > >  1 file changed, 6 insertions(+)
> >> > > > 
> >> > > > diff --git a/arch/arm/mach-socfpga/spl.c
> >> > > > b/arch/arm/mach-socfpga/spl.c index 13ec24b..59fe1f2 100644
> >> > > > --- a/arch/arm/mach-socfpga/spl.c
> >> > > > +++ b/arch/arm/mach-socfpga/spl.c
> >> > > > @@ -181,5 +181,11 @@ void board_init_f(ulong dummy)
> >> > > > 
> >> > > >         /* Configure simple malloc base pointer into RAM. */
> >> > > >         gd->malloc_base = CONFIG_SYS_TEXT_BASE + (1024 * 1024);
> >> > > > 
> >> > > > +       /*
> >> > > > +        * gd->dm_root might contain non-zero value after warm
> >> > > > reset. +        * Clear it to avoid dm_init error
> >> > > > +        */
> >> > > > +       gd->dm_root = NULL;
> >> > > > +
> >> > > > 
> >> > > >         board_init_r(NULL, 0);
> >> > > >  
> >> > > >  }
> >> > > > 
> >> > > > --
> >> > > > 1.9.1
> >> > > 
> >> > > This does not look like the root cause to me. global_data is zeroed
> >> > > by crt0.S if CONFIG_SPL_FRAMEWORK is set, which it seems to be for
> >> > > socfpga.
> >> > > 
> >> > > What boot path does 'warm reset' take?
> >> > 
> >> > Warm reset resets the CPU core(s) and jumps to 0x0 in SRAM (without
> >> > re-reading anything from the boot media).
> >> 
> >> Does that mean it skips crt0.S? How come global_data is not zeroed
> >> there?
> > 
> > No, it does not mean it skips crt0.S . After the warm reset, the bootrom
> > jumps onto the reset vector, so crt0.S (_main) must be executed.
> 
> Then I don't understand the need for this patch.

Apparently, the gd->dm_root is set to a non-NULL address for some (unknown)
reason. I don't quite understand this myself.

The only possibility which can lead to gd->dm_root being set to non-NULL address
is that crt0.S _main is not executed, is that correct ?