On 27 March 2015 at 13:02, Shilpasri G Bhat <[email protected]> wrote: > The power and thermal safety of the system is taken care by an > On-Chip-Controller (OCC) which is real-time subsystem embedded within > the POWER8 processor. OCC continuously monitors the memory and core > temperature, the total system power, state of power supply and fan. > > The cpu frequency can be throttled by OCC for the following reasons: > 1)If a processor crosses its power and temperature limit then OCC will > lower its Pmax to reduce the frequency and voltage. > 2)If OCC crashes then the system is forced to Psafe frequency. > 3)If OCC fails to recover then the kernel is not allowed to do any > further frequency changes and the chip will remain in Psafe. > > The user can see a drop in performance when frequency is throttled and > is unaware of throttling. So detect and report such a condition so > that user can check the OCC status to reboot the system or check for > power supply or fan failures. > > The current status of the core is read from Power Management Status > Register(PMSR) to check if any of the throttling condition is occurred > and the appropriate throttling message is reported. > > Signed-off-by: Shilpasri G Bhat <[email protected]> > --- > Changes from V2: > -Changed commit log to add more details. > -Fixed multi-line comment to proper format > > Changes from V1: Removed unused value of PMCR register > > drivers/cpufreq/powernv-cpufreq.c | 40 > ++++++++++++++++++++++++++++++++++++++- > 1 file changed, 39 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c > b/drivers/cpufreq/powernv-cpufreq.c > index 2dfd4fd..0eb89a9 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -36,7 +36,7 @@ > #define POWERNV_MAX_PSTATES 256 > > static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1]; > -static bool rebooting; > +static bool rebooting, throttled; > > /* > * Note: The set of pstates consists of contiguous integers, the > @@ -294,6 +294,41 @@ static inline unsigned int get_nominal_index(void) > return powernv_pstate_info.max - powernv_pstate_info.nominal; > } > > +static void powernv_cpufreq_throttle_check(unsigned int cpu) > +{ > + unsigned long pmsr; > + int pmsr_pmax, pmsr_lp; > + > + pmsr = get_pmspr(SPRN_PMSR); > + > + /* Check for Pmax Capping */ > + pmsr_pmax = (s8)((pmsr >> 32) & 0xFF); > + if (pmsr_pmax != powernv_pstate_info.max) { > + throttled = true; > + pr_warn("Cpu %d Pmax is reduced to %d\n", cpu, pmsr_pmax); > + } > + > + /* > + * Check for Psafe by reading LocalPstate > + * or check if Psafe_mode_active- 34th bit is set in PMSR. > + */ > + pmsr_lp = (s8)((pmsr >> 48) & 0xFF); > + if ((pmsr_lp < powernv_pstate_info.min) || ((pmsr >> 30) & 1)) { > + throttled = true; > + pr_warn("Cpu %d in Psafe %d PMSR[34]=%lx\n", cpu, > + pmsr_lp, ((pmsr >> 30) & 1)); > + } > + > + /* Check if SPR_EM_DISABLED- 33rd bit is set in PMSR */ > + if ((pmsr >> 31) & 1) { > + throttled = true; > + pr_warn("Frequency management disabled cpu %d PMSR[33]=%lx\n", > + cpu, ((pmsr >> 31) & 1)); > + } > + if (throttled) > + pr_warn("Cpu Frequency is throttled\n"); > +} > + > /* > * powernv_cpufreq_target_index: Sets the frequency corresponding to > * the cpufreq table entry indexed by new_index on the cpus in the > @@ -307,6 +342,9 @@ static int powernv_cpufreq_target_index(struct > cpufreq_policy *policy, > if (unlikely(rebooting) && new_index != get_nominal_index()) > return 0; > > + if (!throttled) > + powernv_cpufreq_throttle_check(smp_processor_id()); > + > freq_data.pstate_id = powernv_freqs[new_index].driver_data;
Acked-by: Viresh Kumar <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
