Hi JC,
Thanks for the review.
On 06/20/2018 02:09 AM, Jayachandran C wrote:
Hi George,
Few comments on your patch:
On Fri, Jun 15, 2018 at 03:03:15AM -0700, 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 <[email protected]>
Acked-by: Viresh Kumar <[email protected]>
---
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 {
+ /*
+ * 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;
+ }
Having this code repeated twice does not look great. Also the math here
is not correct, since (~0 - val2 + val1) is off by one. Because of
binary representation, unsigned subtraction will work even if
val2 < val1. So cleaner way would be to do:
static inline u64 ts_sub(u64 t1, u64 t0)
{
if (t1 > t0 || t0 > ~(u32)0)
return t1 - t0;
return (u32)t1 - (u32)t0;
}
And then use ts_sub in both places above.
I was actually thinking to replace the whole comparison with a single
line irrespective of rollover or not.
It will look something like this.
delta = (u32)(((1UL << 32) - t0) + t1);
This will also take care of the value being off by one.
JC.
Regards,
-George
