[PATCH 1/4] drm/i915/selftests: Verify frequency scaling with RPS
Chris Wilson
chris at chris-wilson.co.uk
Sun Apr 19 11:17:30 UTC 2020
One of the core tenents of reclocking the GPU is that its throughput
scales with the clock frequency. We can observe this by incrementing a
loop counter on the GPU, and compare the different execution rates at
the notional RPS frequencies.
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
drivers/gpu/drm/i915/gt/selftest_gt_pm.c | 3 +-
drivers/gpu/drm/i915/gt/selftest_rps.c | 249 +++++++++++++++++++++--
drivers/gpu/drm/i915/gt/selftest_rps.h | 1 +
3 files changed, 240 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
index 0141c334f2ac..4b2733967c42 100644
--- a/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/selftest_gt_pm.c
@@ -53,8 +53,9 @@ int intel_gt_pm_live_selftests(struct drm_i915_private *i915)
{
static const struct i915_subtest tests[] = {
SUBTEST(live_rc6_manual),
- SUBTEST(live_rps_interrupt),
+ SUBTEST(live_rps_frequency),
SUBTEST(live_rps_power),
+ SUBTEST(live_rps_interrupt),
SUBTEST(live_gt_resume),
};
diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c
index 360f56aa4b82..b1a435db1edc 100644
--- a/drivers/gpu/drm/i915/gt/selftest_rps.c
+++ b/drivers/gpu/drm/i915/gt/selftest_rps.c
@@ -6,6 +6,7 @@
#include <linux/sort.h>
#include "intel_engine_pm.h"
+#include "intel_gpu_commands.h"
#include "intel_gt_pm.h"
#include "intel_rc6.h"
#include "selftest_rps.h"
@@ -17,6 +18,242 @@ static void dummy_rps_work(struct work_struct *wrk)
{
}
+static int cmp_u64(const void *A, const void *B)
+{
+ const u64 *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,
+ u32 **cancel,
+ u32 **counter)
+{
+ enum {
+ COUNT,
+ INC,
+ __NGPR__,
+ };
+#define CS_GPR(x) GEN8_RING_CS_GPR(engine->mmio_base, x)
+ struct drm_i915_gem_object *obj;
+ struct i915_vma *vma;
+ u32 *base, *cs;
+ int loop, i;
+ int err;
+
+ obj = i915_gem_object_create_internal(vm->i915, 4096);
+ if (IS_ERR(obj))
+ return ERR_CAST(obj);
+
+ vma = i915_vma_instance(obj, vm, NULL);
+ if (IS_ERR(vma)) {
+ i915_gem_object_put(obj);
+ return vma;
+ }
+
+ err = i915_vma_pin(vma, 0, 0, PIN_USER);
+ if (err) {
+ i915_vma_put(vma);
+ return ERR_PTR(err);
+ }
+
+ base = i915_gem_object_pin_map(obj, I915_MAP_WC);
+ if (IS_ERR(base)) {
+ i915_gem_object_put(obj);
+ return ERR_CAST(base);
+ }
+ cs = base;
+
+ *cs++ = MI_LOAD_REGISTER_IMM(__NGPR__ * 2);
+ for (i = 0; i < __NGPR__; i++) {
+ *cs++ = i915_mmio_reg_offset(CS_GPR(i));
+ *cs++ = 0;
+ *cs++ = i915_mmio_reg_offset(CS_GPR(i)) + 4;
+ *cs++ = 0;
+ }
+
+ *cs++ = MI_LOAD_REGISTER_IMM(1);
+ *cs++ = i915_mmio_reg_offset(CS_GPR(INC));
+ *cs++ = 1;
+
+ loop = cs - base;
+
+ *cs++ = MI_MATH(4);
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCA, MI_MATH_REG(COUNT));
+ *cs++ = MI_MATH_LOAD(MI_MATH_REG_SRCB, MI_MATH_REG(INC));
+ *cs++ = MI_MATH_ADD;
+ *cs++ = MI_MATH_STORE(MI_MATH_REG(COUNT), MI_MATH_REG_ACCU);
+
+ *cs++ = MI_STORE_REGISTER_MEM_GEN8;
+ *cs++ = i915_mmio_reg_offset(CS_GPR(COUNT));
+ *cs++ = lower_32_bits(vma->node.start + 1000 * sizeof(*cs));
+ *cs++ = upper_32_bits(vma->node.start + 1000 * sizeof(*cs));
+
+ *cs++ = MI_BATCH_BUFFER_START_GEN8;
+ *cs++ = lower_32_bits(vma->node.start + loop * sizeof(*cs));
+ *cs++ = upper_32_bits(vma->node.start + loop * sizeof(*cs));
+
+ i915_gem_object_flush_map(obj);
+
+ *cancel = base + loop;
+ *counter = memset32(base + 1000, 0, 1);
+ return vma;
+}
+
+static u64 __measure_frequency(u32 *cntr, int duration_ms)
+{
+ u64 dc, dt;
+
+ dt = ktime_get();
+ dc = READ_ONCE(*cntr);
+ usleep_range(1000 * duration_ms, 2000 * duration_ms);
+ dc = READ_ONCE(*cntr) - dc;
+ dt = ktime_get() - dt;
+
+ return div64_u64(1000 * 1000 * dc, dt);
+}
+
+static u64 measure_frequency_at(struct intel_rps *rps, u32 *cntr, int *freq)
+{
+ u64 x[5];
+ int i;
+
+ mutex_lock(&rps->lock);
+ GEM_BUG_ON(!rps->active);
+ intel_rps_set(rps, *freq);
+ mutex_unlock(&rps->lock);
+
+ msleep(20); /* more than enough time to stabilise! */
+
+ for (i = 0; i < 5; i++)
+ x[i] = __measure_frequency(cntr, 2);
+ *freq = read_cagf(rps);
+
+ /* 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);
+}
+
+static bool scaled_within(u64 x, u64 y, u32 f_n, u32 f_d)
+{
+ return f_d * x > f_n * y && f_n * x < f_d * y;
+}
+
+int live_rps_frequency(void *arg)
+{
+ void (*saved_work)(struct work_struct *wrk);
+ struct intel_gt *gt = arg;
+ struct intel_rps *rps = >->rps;
+ struct intel_engine_cs *engine;
+ enum intel_engine_id id;
+ int err = 0;
+
+ /*
+ * The premise is that the GPU does change freqency at our behest.
+ * Let's check there is a correspondence between the requested
+ * frequency, the actual frequency, and the observed clock rate.
+ */
+
+ if (!rps->enabled || rps->max_freq <= rps->min_freq)
+ return 0;
+
+ if (INTEL_GEN(gt->i915) < 8) /* for CS simplicity */
+ return 0;
+
+ intel_gt_pm_wait_for_idle(gt);
+ saved_work = rps->work.func;
+ rps->work.func = dummy_rps_work;
+
+ for_each_engine(engine, gt, id) {
+ struct i915_request *rq;
+ struct i915_vma *vma;
+ u32 *cancel, *cntr;
+ struct {
+ u64 count;
+ int freq;
+ } min, max;
+
+ vma = create_spin_counter(engine,
+ engine->kernel_context->vm,
+ &cancel, &cntr);
+ if (IS_ERR(vma)) {
+ err = PTR_ERR(vma);
+ break;
+ }
+
+ rq = intel_engine_create_kernel_request(engine);
+ if (IS_ERR(rq)) {
+ err = PTR_ERR(rq);
+ goto err_vma;
+ }
+
+ i915_vma_lock(vma);
+ err = i915_request_await_object(rq, vma->obj, false);
+ if (!err)
+ err = i915_vma_move_to_active(vma, rq, 0);
+ if (!err)
+ err = rq->engine->emit_bb_start(rq,
+ vma->node.start,
+ PAGE_SIZE, 0);
+ i915_vma_unlock(vma);
+ i915_request_add(rq);
+ if (err)
+ goto err_vma;
+
+ if (wait_for(READ_ONCE(*cntr), 10)) {
+ pr_err("%s: timed loop did not start\n",
+ engine->name);
+ goto err_vma;
+ }
+
+ min.freq = rps->min_freq;
+ min.count = measure_frequency_at(rps, cntr, &min.freq);
+
+ max.freq = rps->max_freq;
+ max.count = measure_frequency_at(rps, cntr, &max.freq);
+
+ pr_info("%s: min:%lluKHz @ %uMHz, max:%lluKHz @ %uMHz [%d%%]\n",
+ engine->name,
+ min.count, intel_gpu_freq(rps, min.freq),
+ max.count, intel_gpu_freq(rps, max.freq),
+ (int)DIV64_U64_ROUND_CLOSEST(100 * min.freq * max.count,
+ max.freq * min.count));
+
+ if (!scaled_within(max.freq * min.count,
+ min.freq * max.count,
+ 1, 2)) {
+ pr_err("%s: CS did not scale with frequency! scaled min:%llu, max:%llu\n",
+ engine->name,
+ max.freq * min.count,
+ min.freq * max.count);
+ err = -EINVAL;
+ }
+
+err_vma:
+ *cancel = MI_BATCH_BUFFER_END;
+ i915_gem_object_unpin_map(vma->obj);
+ i915_vma_unpin(vma);
+ i915_vma_put(vma);
+
+ if (igt_flush_test(gt->i915))
+ err = -EIO;
+ if (err)
+ break;
+ }
+
+ intel_gt_pm_wait_for_idle(gt);
+ rps->work.func = saved_work;
+
+ return err;
+}
+
static void sleep_for_ei(struct intel_rps *rps, int timeout_us)
{
/* Flush any previous EI */
@@ -248,18 +485,6 @@ static u64 __measure_power(int duration_ms)
return div64_u64(1000 * 1000 * dE, dt);
}
-static int cmp_u64(const void *A, const void *B)
-{
- const u64 *a = A, *b = B;
-
- if (a < b)
- return -1;
- else if (a > b)
- return 1;
- else
- return 0;
-}
-
static u64 measure_power_at(struct intel_rps *rps, int freq)
{
u64 x[5];
diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.h b/drivers/gpu/drm/i915/gt/selftest_rps.h
index cad515a7f0e5..07c2bddf8899 100644
--- a/drivers/gpu/drm/i915/gt/selftest_rps.h
+++ b/drivers/gpu/drm/i915/gt/selftest_rps.h
@@ -6,6 +6,7 @@
#ifndef SELFTEST_RPS_H
#define SELFTEST_RPS_H
+int live_rps_frequency(void *arg);
int live_rps_interrupt(void *arg);
int live_rps_power(void *arg);
--
2.20.1
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