arm: ls1021a: Ensure Generic Timer disabled before jumping into the OS

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@whiterocker.com>
Signed-off-by: Alison Wang <alison.wang@freescale.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: York Sun <yorksun@freescale.com>

diff --git a/arch/arm/cpu/armv7/ls102xa/cpu.c b/arch/arm/cpu/armv7/ls102xa/cpu.c
index df2e1b76f168eb4c67e28d591730787277a66ca9..2215fe93cfee424fc50124efda312ed92c64f9ed 100644 (file)
--- a/arch/arm/cpu/armv7/ls102xa/cpu.c
+++ b/arch/arm/cpu/armv7/ls102xa/cpu.c
@@ -372,3 +372,13 @@ void reset_cpu(ulong addr)
                 */
        }
 }
+
+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));
+}