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.cher...@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
