On 9/22/2022 7:32 AM, Riana Tauro wrote:
A fundamental assumption is that at lower frequencies,
not only do we run slower, but we save power compared to
higher frequencies.
live_slpc_power checks if running at low frequency saves power
Signed-off-by: Riana Tauro <riana.tauro@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/selftest_slpc.c | 116 ++++++++++++++++++++++--
1 file changed, 107 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/selftest_slpc.c b/drivers/gpu/drm/i915/gt/selftest_slpc.c
index f8a1d27df272..f22f091d2844 100644
--- a/drivers/gpu/drm/i915/gt/selftest_slpc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_slpc.c
@@ -11,7 +11,8 @@
enum test_type {
VARY_MIN,
VARY_MAX,
- MAX_GRANTED
+ MAX_GRANTED,
+ SLPC_POWER,
};
static int slpc_set_min_freq(struct intel_guc_slpc *slpc, u32 freq)
@@ -41,6 +42,42 @@ static int slpc_set_max_freq(struct intel_guc_slpc *slpc, u32 freq)
return ret;
}
+static int slpc_set_freq(struct intel_gt *gt, u32 freq)
+{
+ int err;
+ struct intel_guc_slpc *slpc = >->uc.guc.slpc;
+
+ err = slpc_set_max_freq(slpc, freq);
+ if (err) {
+ pr_err("Unable to update max freq");
+ return err;
+ }
+
+ err = slpc_set_min_freq(slpc, freq);
+ if (err) {
+ pr_err("Unable to update min freq");
+ return err;
+ }
+
+ return intel_rps_read_actual_frequency(>->rps);
The return value here is overloaded (either -ERR or frequency). Can we
just return the error status here and query the act_freq in the caller
instead?
+}
+
+static u64 measure_slpc_power_at(struct intel_gt *gt, int *freq)
Name is a little misleading, maybe slpc_measure_power_at() ?
+{
+ u64 x[5];
+ int i;
+
+ *freq = slpc_set_freq(gt, *freq);
Here, we can check for return code and then query for act_freq.
+ for (i = 0; i < 5; i++)
+ x[i] = __measure_power(5);
+ *freq = (*freq + intel_rps_read_actual_frequency(>->rps)) / 2;
+
+ /* A simple triangle filter for better result stability */
+ sort(x, 5, sizeof(*x), cmp_u64, NULL);
+
+ return div_u64(x[1] + 2 * x[2] + x[3], 4);
we are duplicating code from selftest_rps here, is it possible to add a
helper instead (like __measure_power())?
+}
+
static int vary_max_freq(struct intel_guc_slpc *slpc, struct intel_rps *rps,
u32 *max_act_freq)
{
@@ -113,6 +150,52 @@ static int vary_min_freq(struct intel_guc_slpc *slpc, struct intel_rps *rps,
return err;
}
+static int slpc_power(struct intel_gt *gt, struct intel_engine_cs *engine)
+{
+ struct intel_guc_slpc *slpc = >->uc.guc.slpc;
+ struct {
+ u64 power;
+ int freq;
+ } min, max;
+ int err = 0;
+
+ /*
+ * Our fundamental assumption is that running at lower frequency
+ * actually saves power. Let's see if our RAPL measurement support
supports*
+ * that theory.
+ */
+ if (!librapl_supported(gt->i915))
+ return 0;
+
+ min.freq = slpc->min_freq;
+ min.power = measure_slpc_power_at(gt, &min.freq);
+
+ max.freq = slpc->rp0_freq;
+ max.power = measure_slpc_power_at(gt, &max.freq);
+
+ pr_info("%s: min:%llumW @ %uMHz, max:%llumW @ %uMHz\n",
+ engine->name,
+ min.power, min.freq,
+ max.power, max.freq);
+
+ if (10 * min.freq >= 9 * max.freq) {
+ pr_notice("Could not control frequency, ran at [%uMHz, %uMhz]\n",
+ min.freq, max.freq);
+ }
+
+ if (11 * min.power > 10 * max.power) {
+ pr_err("%s: did not conserve power when setting lower frequency!\n",
+ engine->name);
+ err = -EINVAL;
+ }
+
+ /* Restore min/max frequencies */
+ slpc_set_max_freq(slpc, slpc->rp0_freq);
+ slpc_set_min_freq(slpc, slpc->min_freq);
+
+ return err;
+}
+
static int max_granted_freq(struct intel_guc_slpc *slpc, struct intel_rps *rps, u32 *max_act_freq)
{
struct intel_gt *gt = rps_to_gt(rps);
@@ -233,17 +316,23 @@ static int run_test(struct intel_gt *gt, int test_type)
err = max_granted_freq(slpc, rps, &max_act_freq);
break;
+
+ case SLPC_POWER:
+ err = slpc_power(gt, engine);
+ break;
}
- pr_info("Max actual frequency for %s was %d\n",
- engine->name, max_act_freq);
+ if (test_type != SLPC_POWER) {
+ pr_info("Max actual frequency for %s was %d\n",
+ engine->name, max_act_freq);
- /* Actual frequency should rise above min */
- if (max_act_freq <= slpc_min_freq) {
- pr_err("Actual freq did not rise above min\n");
- pr_err("Perf Limit Reasons: 0x%x\n",
- intel_uncore_read(gt->uncore, GT0_PERF_LIMIT_REASONS));
- err = -EINVAL;
+ /* Actual frequency should rise above min */
+ if (max_act_freq <= slpc_min_freq) {
+ pr_err("Actual freq did not rise above min\n");
+ pr_err("Perf Limit Reasons: 0x%x\n",
+ intel_uncore_read(gt->uncore, GT0_PERF_LIMIT_REASONS));
+ err = -EINVAL;
+ }
}
igt_spinner_end(&spin);
@@ -292,12 +381,21 @@ static int live_slpc_max_granted(void *arg)
return run_test(gt, MAX_GRANTED);
}
+static int live_slpc_power(void *arg)
+{
+ struct drm_i915_private *i915 = arg;
+ struct intel_gt *gt = to_gt(i915);
+
+ return run_test(gt, SLPC_POWER);
+}
+
int intel_slpc_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
SUBTEST(live_slpc_vary_max),
SUBTEST(live_slpc_vary_min),
SUBTEST(live_slpc_max_granted),
+ SUBTEST(live_slpc_power),
Thanks,
Vinay.
};
if (intel_gt_is_wedged(to_gt(i915)))
