[U-Boot] arm: ls1021a: Ensure LS1021 ARM Generic Timer CompareValue Set 64-bit

[Alexander Stein]

On Wednesday 15 July 2015 15:13:05, 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.
> At any rate this patch makes the manipulation explicitly 64-bit which
> alleviates the issue.

initcall_run_list is the function "hiding" or not "hiding" this problem when 
calling timer_init. It is using r4 and r5 for it's loop variables. On gcc-4.8 
and gcc-4.9 the usage of those two registers are switched. So a newer gcc uses 
a slightly different register allocation. While this function is perfectly 
fine, depending on the r4 register timer_init uses a different value for the 
upper 32-bit of CNTP_CVAL resulting in the different behavior.
I've compared two u-boots objdumps showing and not showing this problem which 
_only_ differ in those 2 register usages.

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

Legal and Commercial Address:
Am Windrad 2
08468 Heinsdorfergrund
Germany

Office: +49 (0) 3765 38600-0
Fax:    +49 (0) 3765 38600-4100
 
Managing Directors:
	Director Technology/CEO: Dipl.-Phys. Siegmar Schmidt;
	Director Commercial Affairs/COO: Dipl. Ing. (FH) Armin von Collrepp
Commercial Registry:
	Amtsgericht Chemnitz, HRB 28082; USt.-Id Nr. DE150534010