[PATCH v1 4/4] cpufreq: intel_pstate: Implement the ->adjust_perf() callback

Rafael J. Wysocki
2020-12-07T16:40:32Z

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Make intel_pstate expose the ->adjust_perf() callback when it
operates in the passive mode with HWP enabled which causes the
schedutil governor to use that callback instead of ->fast_switch().

The minimum and target performance-level values passed by the
governor to ->adjust_perf() are converted to HWP.REQ.MIN and
HWP.REQ.DESIRED, respectively, which allows the processor to
adjust its configuration to maximize energy-efficiency while
providing sufficient capacity.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Changes with respect to the RFC:
- Drop the code related to the dropped "busy" argument of
->adjust_perf().
- Update the changelog accordingly.

---
drivers/cpufreq/intel_pstate.c | 70 +++++++++++++++++++++++++++++++++--------
1 file changed, 58 insertions(+), 12 deletions(-)

Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -2526,20 +2526,19 @@ static void intel_cpufreq_trace(struct c
fp_toint(cpu->iowait_boost * 100));
}

-static void intel_cpufreq_adjust_hwp(struct cpudata *cpu, u32 target_pstate,
- bool strict, bool fast_switch)
+static void intel_cpufreq_adjust_hwp(struct cpudata *cpu, u32 min, u32 max,
+ u32 desired, bool fast_switch)
{
u64 prev = READ_ONCE(cpu->hwp_req_cached), value = prev;

value &= ~HWP_MIN_PERF(~0L);
- value |= HWP_MIN_PERF(target_pstate);
+ value |= HWP_MIN_PERF(min);

- /*
- * The entire MSR needs to be updated in order to update the HWP min
- * field in it, so opportunistically update the max too if needed.
- */
value &= ~HWP_MAX_PERF(~0L);
- value |= HWP_MAX_PERF(strict ? target_pstate : cpu->max_perf_ratio);
+ value |= HWP_MAX_PERF(max);
+
+ value &= ~HWP_DESIRED_PERF(~0L);
+ value |= HWP_DESIRED_PERF(desired);

if (value == prev)
return;
@@ -2569,11 +2568,15 @@ static int intel_cpufreq_update_pstate(s
int old_pstate = cpu->pstate.current_pstate;

target_pstate = intel_pstate_prepare_request(cpu, target_pstate);
- if (hwp_active)
- intel_cpufreq_adjust_hwp(cpu, target_pstate,
- policy->strict_target, fast_switch);
- else if (target_pstate != old_pstate)
+ if (hwp_active) {
+ int max_pstate = policy->strict_target ?
+ target_pstate : cpu->max_perf_ratio;
+
+ intel_cpufreq_adjust_hwp(cpu, target_pstate, max_pstate, 0,
+ fast_switch);
+ } else if (target_pstate != old_pstate) {
intel_cpufreq_adjust_perf_ctl(cpu, target_pstate, fast_switch);
+ }

cpu->pstate.current_pstate = target_pstate;

@@ -2634,6 +2637,47 @@ static unsigned int intel_cpufreq_fast_s
return target_pstate * cpu->pstate.scaling;
}

+static void intel_cpufreq_adjust_perf(unsigned int cpunum,
+ unsigned long min_perf,
+ unsigned long target_perf,
+ unsigned long capacity)
+{
+ struct cpudata *cpu = all_cpu_data[cpunum];
+ int old_pstate = cpu->pstate.current_pstate;
+ int cap_pstate, min_pstate, max_pstate, target_pstate;
+
+ update_turbo_state();
+ cap_pstate = global.turbo_disabled ? cpu->pstate.max_pstate :
+ cpu->pstate.turbo_pstate;
+
+ /* Optimization: Avoid unnecessary divisions. */
+
+ target_pstate = cap_pstate;
+ if (target_perf < capacity)
+ target_pstate = DIV_ROUND_UP(cap_pstate * target_perf, capacity);
+
+ min_pstate = cap_pstate;
+ if (min_perf < capacity)
+ min_pstate = DIV_ROUND_UP(cap_pstate * min_perf, capacity);
+
+ if (min_pstate < cpu->pstate.min_pstate)
+ min_pstate = cpu->pstate.min_pstate;
+
+ if (min_pstate < cpu->min_perf_ratio)
+ min_pstate = cpu->min_perf_ratio;
+
+ max_pstate = min(cap_pstate, cpu->max_perf_ratio);
+ if (max_pstate < min_pstate)
+ max_pstate = min_pstate;
+
+ target_pstate = clamp_t(int, target_pstate, min_pstate, max_pstate);
+
+ intel_cpufreq_adjust_hwp(cpu, min_pstate, max_pstate, target_pstate, true);
+
+ cpu->pstate.current_pstate = target_pstate;
+ intel_cpufreq_trace(cpu, INTEL_PSTATE_TRACE_FAST_SWITCH, old_pstate);
+}
+
static int intel_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
int max_state, turbo_max, min_freq, max_freq, ret;
@@ -3032,6 +3076,8 @@ static int __init intel_pstate_init(void
intel_pstate.attr = hwp_cpufreq_attrs;
intel_cpufreq.attr = hwp_cpufreq_attrs;
intel_cpufreq.flags |= CPUFREQ_NEED_UPDATE_LIMITS;
+ intel_cpufreq.fast_switch = NULL;
+ intel_cpufreq.adjust_perf = intel_cpufreq_adjust_perf;
if (!default_driver)
default_driver = &intel_pstate;