drm/i915: load a ring frequency scaling table v3

The ring frequency scaling table tells the PCU to treat certain GPU
frequencies as if they were a given CPU frequency for purposes of
scaling the ring frequency.  Normally the PCU will scale the ring
frequency based on the CPU P-state, but with the table present, it will
also take the GPU frequency into account.

The main downside of keeping the ring frequency high while the CPU is
at a low frequency (or asleep altogether) is increased power
consumption.  But then if you're keeping your GPU busy, you probably
want the extra performance.

v2:
  - add units to debug table header (from Eric)
  - use tsc_khz as a fallback if the cpufreq driver doesn't give us a freq
    (from Chris)
v3:
  - fix comments & debug output
  - remove unneeded force wake get/put

Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Tested-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 4d46441cbe2d..8a5a032ec696 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1123,6 +1123,44 @@ static int i915_emon_status(struct seq_file *m, void *unused)
 	return 0;
 }
 
+static int i915_ring_freq_table(struct seq_file *m, void *unused)
+{
+	struct drm_info_node *node = (struct drm_info_node *) m->private;
+	struct drm_device *dev = node->minor->dev;
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	int ret;
+	int gpu_freq, ia_freq;
+
+	if (!IS_GEN6(dev)) {
+		seq_printf(m, "unsupported on this chipset\n");
+		return 0;
+	}
+
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
+
+	seq_printf(m, "GPU freq (MHz)\tEffective CPU freq (MHz)\n");
+
+	for (gpu_freq = dev_priv->min_delay; gpu_freq <= dev_priv->max_delay;
+	     gpu_freq++) {
+		I915_WRITE(GEN6_PCODE_DATA, gpu_freq);
+		I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_PCODE_READY |
+			   GEN6_PCODE_READ_MIN_FREQ_TABLE);
+		if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) &
+			      GEN6_PCODE_READY) == 0, 10)) {
+			DRM_ERROR("pcode read of freq table timed out\n");
+			continue;
+		}
+		ia_freq = I915_READ(GEN6_PCODE_DATA);
+		seq_printf(m, "%d\t\t%d\n", gpu_freq * 50, ia_freq * 100);
+	}
+
+	mutex_unlock(&dev->struct_mutex);
+
+	return 0;
+}
+
 static int i915_gfxec(struct seq_file *m, void *unused)
 {
 	struct drm_info_node *node = (struct drm_info_node *) m->private;
@@ -1426,6 +1464,7 @@ static struct drm_info_list i915_debugfs_list[] = {
 	{"i915_inttoext_table", i915_inttoext_table, 0},
 	{"i915_drpc_info", i915_drpc_info, 0},
 	{"i915_emon_status", i915_emon_status, 0},
+	{"i915_ring_freq_table", i915_ring_freq_table, 0},
 	{"i915_gfxec", i915_gfxec, 0},
 	{"i915_fbc_status", i915_fbc_status, 0},
 	{"i915_sr_status", i915_sr_status, 0},