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

[Alexander Stein]

Hello Alison,

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/014400.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?

Best regards,
Alexander
-- 
Dipl.-Inf. Alexander Stein
SYS TEC electronic GmbH
alexander.stein at systec-electronic.com

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