[U-Boot] arm: ls1021a: Ensure Generic Timer disabled before jumping into the OS

[Huan Wang]

Hi, Alexander,

> On Tuesday 04 August 2015 09:55:37, Alison Wang wrote:
> > This patch addresses a problem mentioned recently on this mailing
> list:
> > [1].
> >
> > In that posting a LS1021 based system was locking up at about 5
> > minutes after boot,but the problem was mysteriously related to the
> > toolchain used for building u-boot.Debugging the problem reveals a
> > stuck interrupt 29 on the GIC.
> >
> > It appears Freescale's LS1021 support in u-boot erroneously sets the
> > 64-bit ARM generic PL1 physical time CompareValue register to all-
> ones
> > with a 32-bit value.This causes the timer compare to fire 344 seconds
> > after u-boot configures it.Depending on how fast u-boot gets the
> > kernel booted,this amounts to about 5-minutes of Linux uptime before
> > locking up.
> >
> > Apparently the bug is masked by some toolchains. Perhaps this is
> > explained by default compiler options, word sizes, or binutils
> versions.
> >
> > To fix the above issue, the generic physical timer is disabled before
> > jumping to the OS.
> >
> > [1]
> > https://lists.yoctoproject.org/pipermail/meta-freescale/2015-
> June/0144
> > 00.html
> >
> > Signed-off-by: Chris Kilgour <techie at whiterocker.com>
> > Signed-off-by: Alison Wang <alison.wang at freescale.com>
> > ---
> >  arch/arm/cpu/armv7/ls102xa/cpu.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/arm/cpu/armv7/ls102xa/cpu.c
> > b/arch/arm/cpu/armv7/ls102xa/cpu.c
> > index 75f0d8c..298422f 100644
> > --- a/arch/arm/cpu/armv7/ls102xa/cpu.c
> > +++ b/arch/arm/cpu/armv7/ls102xa/cpu.c
> > @@ -346,3 +346,13 @@ void smp_kick_all_cpus(void)
> >  	out_be32(&gur->brrl, 0x2);
> >  }
> >  #endif
> > +
> > +void arch_preboot_os(void)
> > +{
> > +	unsigned long ctrl;
> > +
> > +	/* Disable PL1 Physical Timer */
> > +	asm("mrc p15, 0, %0, c14, c2, 1" : "=r" (ctrl));
> > +	ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
> > +	asm("mcr p15, 0, %0, c14, c2, 1" : : "r" (ctrl)); }
> 
> This only disables the timer when booting linux. Does the possibly
> misconfigured timer compare value (only lower 32-bits are set to
> 0xffffffff) have any side-effects within u-boot? I don't currently know
> the timer is used there.
> I would prefer that the inline assembly code in timer_init is fixed to
> pass an 64-bit variable to mcrr. Maybe someone will take that code
> snippet as an example and such problems occur again. Opinions?
> 

[Alison Wang] Thanks for your reply. I agree with you that the misconfigured
Timer compare value should be fixed too. So except this patch, the patch on
http://patchwork.ozlabs.org/patch/495476/ need to be applied too.


Best Regards,
Alison Wang