From 8757797ff9c97e846348db634e849e11769e5d3d Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 4 May 2020 05:48:47 +0100 Subject: [PATCH] drm/i915/selftests: Repeat the rps clock frequency measurement Repeat the measurement of the clock frequency a few times and use the median to try and reduce the systematic measurement error. Signed-off-by: Chris Wilson Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20200504044903.7626-6-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/gt/selftest_rps.c | 54 +++++++++++++++++++------- 1 file changed, 40 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c index b89a7d7611f6d..bfa1a15564f73 100644 --- a/drivers/gpu/drm/i915/gt/selftest_rps.c +++ b/drivers/gpu/drm/i915/gt/selftest_rps.c @@ -56,6 +56,18 @@ static int cmp_u64(const void *A, const void *B) return 0; } +static int cmp_u32(const void *A, const void *B) +{ + const u32 *a = A, *b = B; + + if (a < b) + return -1; + else if (a > b) + return 1; + else + return 0; +} + static struct i915_vma * create_spin_counter(struct intel_engine_cs *engine, struct i915_address_space *vm, @@ -236,8 +248,8 @@ int live_rps_clock_interval(void *arg) for_each_engine(engine, gt, id) { unsigned long saved_heartbeat; struct i915_request *rq; - ktime_t dt; u32 cycles; + u64 dt; if (!intel_engine_can_store_dword(engine)) continue; @@ -286,15 +298,29 @@ int live_rps_clock_interval(void *arg) engine->name); err = -ENODEV; } else { - preempt_disable(); - dt = ktime_get(); - cycles = -intel_uncore_read_fw(gt->uncore, - GEN6_RP_CUR_UP_EI); - udelay(1000); - dt = ktime_sub(ktime_get(), dt); - cycles += intel_uncore_read_fw(gt->uncore, - GEN6_RP_CUR_UP_EI); - preempt_enable(); + ktime_t dt_[5]; + u32 cycles_[5]; + int i; + + for (i = 0; i < 5; i++) { + preempt_disable(); + + dt_[i] = ktime_get(); + cycles_[i] = -intel_uncore_read_fw(gt->uncore, GEN6_RP_CUR_UP_EI); + + udelay(1000); + + dt_[i] = ktime_sub(ktime_get(), dt_[i]); + cycles_[i] += intel_uncore_read_fw(gt->uncore, GEN6_RP_CUR_UP_EI); + + preempt_enable(); + } + + /* Use the median of both cycle/dt; close enough */ + sort(cycles_, 5, sizeof(*cycles_), cmp_u32, NULL); + cycles = (cycles_[1] + 2 * cycles_[2] + cycles_[3]) / 4; + sort(dt_, 5, sizeof(*dt_), cmp_u64, NULL); + dt = div_u64(dt_[1] + 2 * dt_[2] + dt_[3], 4); } intel_uncore_write_fw(gt->uncore, GEN6_RP_CONTROL, 0); @@ -306,14 +332,14 @@ int live_rps_clock_interval(void *arg) if (err == 0) { u64 time = intel_gt_pm_interval_to_ns(gt, cycles); u32 expected = - intel_gt_ns_to_pm_interval(gt, ktime_to_ns(dt)); + intel_gt_ns_to_pm_interval(gt, dt); pr_info("%s: rps counted %d C0 cycles [%lldns] in %lldns [%d cycles], using GT clock frequency of %uKHz\n", - engine->name, cycles, time, ktime_to_ns(dt), expected, + engine->name, cycles, time, dt, expected, gt->clock_frequency / 1000); - if (10 * time < 8 * ktime_to_ns(dt) || - 8 * time > 10 * ktime_to_ns(dt)) { + if (10 * time < 8 * dt || + 8 * time > 10 * dt) { pr_err("%s: rps clock time does not match walltime!\n", engine->name); err = -EINVAL; -- 2.39.5