Hi Prakash,
Thanks for the review.
On 06/19/2018 01:51 AM, Prakash, Prashanth wrote:
External Email
Hi George,
On 6/15/2018 4:03 AM, George Cherian wrote:
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>
Acked-by: Viresh Kumar <viresh.ku...@linaro.org>
---
drivers/cpufreq/cppc_cpufreq.c | 71 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 71 insertions(+)
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 3464580..3fe7625 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -296,10 +296,81 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy
*policy)
return ret;
}
+static int cppc_get_rate_from_fbctrs(struct cppc_cpudata *cpu,
+ struct cppc_perf_fb_ctrs fb_ctrs_t0,
+ struct cppc_perf_fb_ctrs fb_ctrs_t1)
+{
+ u64 delta_reference, delta_delivered;
+ u64 reference_perf, delivered_perf;
+
+ 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 {
There should be another if () here to check if the reference counters are equal.
We cannot assume, there was a overflow when the counters are equal. As I
mentioned on last patch, the counters *may* pause in idle states.
My Bad... I somehow, over looked that point. In case of delta_reference
being zero there is actually a check below to avoid divide-by-zero.
There I returned reference perf instead of desired perf, same I will
take care in v3. Isn't that sufficient or is there a need for an
explicit check here for delta = zero?
Moreover the delta calculation am planning to replace with single
line comparison in v3 for both normal and overflow case.
+ /*
+ * Counters would have wrapped-around
+ * We also need to find whether the low level fw
+ * maintains 32 bit or 64 bit counters, to calculate
+ * the correct delta.
+ */
+ if (fb_ctrs_t0.reference > (~(u32)0))
+ delta_reference = (~((u64)0) - fb_ctrs_t0.reference) +
+ fb_ctrs_t1.reference;
+ else
+ delta_reference = (~((u32)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
+ * We also need to find whether the low level fw
+ * maintains 32 bit or 64 bit counters, to calculate
+ * the correct delta.
+ */
+ if (fb_ctrs_t0.delivered > (~(u32)0))
+ delta_delivered = (~((u64)0) - fb_ctrs_t0.delivered) +
+ fb_ctrs_t1.delivered;
+ else
+ delta_delivered = (~((u32)0) - fb_ctrs_t0.delivered) +
+ fb_ctrs_t1.delivered;
+ }
+
+ if (delta_reference) /* Check to avoid divide-by zero */
+ delivered_perf = (reference_perf * delta_delivered) /
+ delta_reference;
+ else
+ delivered_perf = reference_perf;
If we cannot compute delivered performance then we should return
desired/requested perf and not reference_perf.
Noted!!
+
+ return cppc_cpufreq_perf_to_khz(cpu, delivered_perf);
+}
+
+static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum)
+{
+ struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};
+ struct cppc_cpudata *cpu = all_cpu_data[cpunum];
+ int ret;
+
+ ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t0);
+ if (ret)
+ return ret;
+
+ udelay(2); /* 2usec delay between sampling */
+
+ ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t1);
+ if (ret)
+ return ret;
+
+ return cppc_get_rate_from_fbctrs(cpu, 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",
Thanks,
Prashanth
Thanks,
-George
