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Subject[RFC/RFT] [PATCH v2 1/6] cpufreq: intel_pstate: Cache last HWP capability/request value
Date
Store the HWP request value last set using MSR_HWP_REQUEST. This will
allow us to save cycles used for reading last HWP request value for
dynamic update of MSR_HWP_REQUEST.
Also store HWP capability MSR value in local memory, to avoid reading
MSR later for calculating limits for dynamic update of MSR_HWP_REQUEST.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
drivers/cpufreq/intel_pstate.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 17e566afbb41..baed29c768e7 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -221,6 +221,8 @@ struct global_params {
* preference/bias
* @epp_saved: Saved EPP/EPB during system suspend or CPU offline
* operation
+ * @hwp_req_cached: Cached value of the last HWP Request MSR
+ * @hwp_cap_cached: Cached value of the last HWP Capabilities MSR
*
* This structure stores per CPU instance data for all CPUs.
*/
@@ -253,6 +255,8 @@ struct cpudata {
s16 epp_policy;
s16 epp_default;
s16 epp_saved;
+ u64 hwp_req_cached;
+ u64 hwp_cap_cached;
};

static struct cpudata **all_cpu_data;
@@ -689,6 +693,7 @@ static void intel_pstate_get_hwp_max(unsigned int cpu, int *phy_max,
u64 cap;

rdmsrl_on_cpu(cpu, MSR_HWP_CAPABILITIES, &cap);
+ WRITE_ONCE(all_cpu_data[cpu]->hwp_cap_cached, cap);
if (global.no_turbo)
*current_max = HWP_GUARANTEED_PERF(cap);
else
@@ -763,6 +768,7 @@ static void intel_pstate_hwp_set(unsigned int cpu)
intel_pstate_set_epb(cpu, epp);
}
skip_epp:
+ WRITE_ONCE(cpu_data->hwp_req_cached, value);
wrmsrl_on_cpu(cpu, MSR_HWP_REQUEST, value);
}

--
2.13.6
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