[U-Boot] [PATCH] ARM: global_data: make tbl long long
From: Dirk Behme dirk.behme@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.
Signed-off-by: Knut Wohlrab knut.wohlrab@de.bosch.com Signed-off-by: Dirk Behme dirk.behme@de.bosch.com --- arch/arm/include/asm/global_data.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/global_data.h b/arch/arm/include/asm/global_data.h index 37ac0da..1099af9 100644 --- a/arch/arm/include/asm/global_data.h +++ b/arch/arm/include/asm/global_data.h @@ -41,7 +41,7 @@ struct arch_global_data { /* "static data" needed by most of timer.c on ARM platforms */ unsigned long timer_rate_hz; unsigned long tbu; - unsigned long tbl; + unsigned long long tbl; unsigned long lastinc; unsigned long long timer_reset_value; #ifdef CONFIG_IXP425
Dear Dirk Behme,
In message 1362387637-32334-1-git-send-email-dirk.behme@de.bosch.com you wrote:
From: Dirk Behme dirk.behme@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
Dear Wolfgang,
On 04.03.2013 12:10, Wolfgang Denk wrote:
Dear Dirk Behme,
In message 1362387637-32334-1-git-send-email-dirk.behme@de.bosch.com you wrote:
From: Dirk Behme dirk.behme@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
Dear Dirk,
In message 5134ADB7.2000106@de.bosch.com you wrote:
Many thanks for this explanation!
You are welcome...
This patch is obsolete now, replaced by
Thanks, looks good to me. I hesitate to add an Acked-by: or even Reviewed-by: as this timer stuff on ARM is a bit of black magic to me...
Best regards,
Wolfgang Denk
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Dirk Behme -
Wolfgang Denk