Messages in this thread Patch in this message | | | From | George Cherian <> | Subject | [PATCH] cpufreq / CPPC: Add cpuinfo_cur_freq support for CPPC | Date | Tue, 22 May 2018 04:42:04 -0700 |
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Per Section 8.4.7.1.3 of ACPI 6.2, The platform provides performance feedback via set of performance counters. To determine the actual performance level delivered over time, OSPM may read a set of performance counters from the Reference Performance Counter Register and the Delivered Performance Counter Register.
OSPM calculates the delivered performance over a given time period by taking a beginning and ending snapshot of both the reference and delivered performance counters, and calculating:
delivered_perf = reference_perf X (delta of delivered_perf counter / delta of reference_perf counter).
Implement the above and hook this to the cpufreq->get method.
Signed-off-by: George Cherian <george.cherian@cavium.com> --- drivers/cpufreq/cppc_cpufreq.c | 44 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+)
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index b15115a..a046915 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -240,10 +240,54 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy) return ret; } +static int cppc_get_rate_from_fbctrs(struct cppc_perf_fb_ctrs fb_ctrs_t0, + struct cppc_perf_fb_ctrs fb_ctrs_t1) +{ + u64 delta_reference, delta_delivered; + u64 reference_perf, ratio; + + reference_perf = fb_ctrs_t0.reference_perf; + if (fb_ctrs_t1.reference > fb_ctrs_t0.reference) + delta_reference = fb_ctrs_t1.reference - fb_ctrs_t0.reference; + else /* Counters would have wrapped-around */ + delta_reference = ((u64)(~((u64)0)) - fb_ctrs_t0.reference) + + fb_ctrs_t1.reference; + + if (fb_ctrs_t1.delivered > fb_ctrs_t0.delivered) + delta_delivered = fb_ctrs_t1.delivered - fb_ctrs_t0.delivered; + else /* Counters would have wrapped-around */ + delta_delivered = ((u64)(~((u64)0)) - fb_ctrs_t0.delivered) + + fb_ctrs_t1.delivered; + + if (delta_reference) /* Check to avoid divide-by zero */ + ratio = (delta_delivered * 1000) / delta_reference; + else + return -EINVAL; + + return (reference_perf * ratio) / 1000; +} + +static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum) +{ + struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0}; + int ret; + + ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t0); + if (ret) + return ret; + + ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t1); + if (ret) + return ret; + + return cppc_get_rate_from_fbctrs(fb_ctrs_t0, fb_ctrs_t1); +} + static struct cpufreq_driver cppc_cpufreq_driver = { .flags = CPUFREQ_CONST_LOOPS, .verify = cppc_verify_policy, .target = cppc_cpufreq_set_target, + .get = cppc_cpufreq_get_rate, .init = cppc_cpufreq_cpu_init, .stop_cpu = cppc_cpufreq_stop_cpu, .name = "cppc_cpufreq", -- 1.8.3.1
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