Re: [PATCH v3 5/6] cpufreq: powernv: Report Psafe only if PMSR.psafe_mode_active bit is set

Preeti U Murthy
2015-05-05T03:46:22Z

On 05/04/2015 02:24 PM, Shilpasri G Bhat wrote:
> On a reset cycle of OCC, although the system retires from safe
> frequency state the local pstate is not restored to Pmin or last
> requested pstate. Now if the cpufreq governor initiates a pstate
> change, the local pstate will be in Psafe and we will be reporting a
> false positive when we are not throttled.
>
> So in powernv_cpufreq_throttle_check() remove the condition which
> checks if local pstate is less than Pmin while checking for Psafe
> frequency. If the cpus are forced to Psafe then PMSR.psafe_mode_active
> bit will be set. So, when OCCs become active this bit will be cleared.
> Let us just rely on this bit for reporting throttling.
>
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> ---
> drivers/cpufreq/powernv-cpufreq.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index 9618813..0a59d5b 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -39,7 +39,6 @@
> #define PMSR_PSAFE_ENABLE (1UL << 30)
> #define PMSR_SPR_EM_DISABLE (1UL << 31)
> #define PMSR_MAX(x) ((x >> 32) & 0xFF)
> -#define PMSR_LP(x) ((x >> 48) & 0xFF)
> #define OCC_RESET 0
> #define OCC_LOAD 1
> #define OCC_THROTTLE 2
> @@ -316,7 +315,7 @@ static void powernv_cpufreq_throttle_check(void *data)
> {
> unsigned int cpu = smp_processor_id();
> unsigned long pmsr;
> - int pmsr_pmax, pmsr_lp, i;
> + int pmsr_pmax, i;
>
> pmsr = get_pmspr(SPRN_PMSR);
>
> @@ -338,14 +337,9 @@ static void powernv_cpufreq_throttle_check(void *data)
> chips[i].id, pmsr_pmax);
> }
>
> - /*
> - * Check for Psafe by reading LocalPstate
> - * or check if Psafe_mode_active is set in PMSR.
> - */
> + /* Check if Psafe_mode_active is set in PMSR. */
> next:
> - pmsr_lp = (s8)PMSR_LP(pmsr);
> - if ((pmsr_lp < powernv_pstate_info.min) ||
> - (pmsr & PMSR_PSAFE_ENABLE)) {
> + if (pmsr & PMSR_PSAFE_ENABLE) {
> throttled = true;
> pr_info("Pstate set to safe frequency\n");
> }
>

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>