On 14-05-07 07:50 PM, Doug Anderson wrote:
> The loops_per_jiffy count continues to be updated as each CPU is
> brought up. This causes problems when we've got an HMP system and
> different CPUs have different loops per jiffy. On exynos 542x
> systems, for instance, the A7s will have significantly lower loops per
> jiffy than their big brothers.
Based on the other discussion for the ARM variant of this, I'm
assuming this also becomes a WFC issue. And if not, then it
probably should go by John or similar ; getmaintainers is just
being dumb in spitting my name out, since I only made one
trivial change to this file a year ago or similar.
P.
--
>
> We should always set the loops_per_jiffy the first time through, then
> use the max.
>
> One could argue that complex HMP systems should really be completely
> ignoring the global loops_per_jiffy variable anyway. That's probably
> why nobody has fixed this before. With that argument you could say
> that while this change isn't incorrect, it's a bit misguided. Still,
> it doesn't hurt and provides a better fallback than we had without
> this.
>
> Signed-off-by: Doug Anderson <diand...@chromium.org>
> ---
> init/calibrate.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/init/calibrate.c b/init/calibrate.c
> index 520702d..073bf9b 100644
> --- a/init/calibrate.c
> +++ b/init/calibrate.c
> @@ -265,40 +265,44 @@ unsigned long __attribute__((weak))
> calibrate_delay_is_known(void)
> void calibrate_delay(void)
> {
> unsigned long lpj;
> - static bool printed;
> + static bool already_ran;
> int this_cpu = smp_processor_id();
>
> if (per_cpu(cpu_loops_per_jiffy, this_cpu)) {
> lpj = per_cpu(cpu_loops_per_jiffy, this_cpu);
> - if (!printed)
> + if (!already_ran)
> pr_info("Calibrating delay loop (skipped) "
> "already calibrated this CPU");
> } else if (preset_lpj) {
> lpj = preset_lpj;
> - if (!printed)
> + if (!already_ran)
> pr_info("Calibrating delay loop (skipped) "
> "preset value.. ");
> - } else if ((!printed) && lpj_fine) {
> + } else if ((!already_ran) && lpj_fine) {
> lpj = lpj_fine;
> pr_info("Calibrating delay loop (skipped), "
> "value calculated using timer frequency.. ");
> } else if ((lpj = calibrate_delay_is_known())) {
> ;
> } else if ((lpj = calibrate_delay_direct()) != 0) {
> - if (!printed)
> + if (!already_ran)
> pr_info("Calibrating delay using timer "
> "specific routine.. ");
> } else {
> - if (!printed)
> + if (!already_ran)
> pr_info("Calibrating delay loop... ");
> lpj = calibrate_delay_converge();
> }
> per_cpu(cpu_loops_per_jiffy, this_cpu) = lpj;
> - if (!printed)
> + if (!already_ran) {
> pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n",
> lpj/(500000/HZ),
> (lpj/(5000/HZ)) % 100, lpj);
>
> - loops_per_jiffy = lpj;
> - printed = true;
> + loops_per_jiffy = lpj;
> + } else {
> + loops_per_jiffy = max(loops_per_jiffy, lpj);
> + }
> +
> + already_ran = true;
> }
>
--
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