[U-Boot] [PATCH] ARM: global_data: make tbl long long

[Wolfgang Denk]

Dear Dirk Behme,

In message <1362387637-32334-1-git-send-email-dirk.behme at de.bosch.com> you wrote:
> From: Dirk Behme <dirk.behme at de.bosch.com>
> 
> Several ARM timer implementations use gd->arch.tbl to record the
> absolute tick count of 32-bit counters, including timer overflows.
> For example arch/arm/imx-common/timer.c does:
> 
> ulong lastinc;
> ulong now = counter value;
> if (no overflow) {
> 	...
> } else { /* counter overflow */
> 	gd->arch.tbl += (0xFFFFFFFF - lastinc) + now;
> }
> lastinc =  now;
> 
> As we use a 32-bit counter and the two ulong (32-bit) variables 'lastinc'
> and 'now' here, gd->arch.tbl should be long long (64-bit) to not overflow
> at the same time, too.

I think this is wrong.

"tbl" means "time base, lower 32 bits" and is complemented by "tbu"
(time base, upper 32 bits) to form a 64 bit time base counter.

If you need the full 64 bit precision, then please either maintain the
carry manually, or use a proper union or similar.

Best regards,

Wolfgang Denk

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