Dear Wolfgang,
On 04.03.2013 12:10, Wolfgang Denk wrote:
Dear Dirk Behme,
In message <1362387637-32334-1-git-send-email-dirk.be...@de.bosch.com> you
wrote:
From: Dirk Behme <dirk.be...@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.
Many thanks for this explanation!
This patch is obsolete now, replaced by
http://patchwork.ozlabs.org/patch/224740/
Thanks
Dirk
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