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>

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},

drivers/gpu/drm/i915/i915_reg.h

@@ -3434,7 +3434,9 @@
 #define GEN6_PCODE_MAILBOX			0x138124
 #define   GEN6_PCODE_READY			(1<<31)
 #define   GEN6_READ_OC_PARAMS			0xc
-#define   GEN6_PCODE_WRITE_MIN_FREQ_TABLE	0x9
+#define   GEN6_PCODE_WRITE_MIN_FREQ_TABLE	0x8
+#define   GEN6_PCODE_READ_MIN_FREQ_TABLE	0x9
 #define GEN6_PCODE_DATA				0x138128
+#define   GEN6_PCODE_FREQ_IA_RATIO_SHIFT	8
 
 #endif /* _I915_REG_H_ */

drivers/gpu/drm/i915/i915_suspend.c

@@ -875,8 +875,10 @@ int i915_restore_state(struct drm_device *dev)
 		intel_init_emon(dev);
 	}
 
-	if (IS_GEN6(dev))
+	if (IS_GEN6(dev)) {
 		gen6_enable_rps(dev_priv);
+		gen6_update_ring_freq(dev_priv);
+	}
 
 	/* Cache mode state */
 	I915_WRITE (CACHE_MODE_0, dev_priv->saveCACHE_MODE_0 | 0xffff0000);

drivers/gpu/drm/i915/intel_display.c

@@ -24,6 +24,7 @@
  *	Eric Anholt <eric@anholt.net>
  */
 
+#include <linux/cpufreq.h>
 #include <linux/module.h>
 #include <linux/input.h>
 #include <linux/i2c.h>
@@ -7273,6 +7274,59 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
 	mutex_unlock(&dev_priv->dev->struct_mutex);
 }
 
+void gen6_update_ring_freq(struct drm_i915_private *dev_priv)
+{
+	int min_freq = 15;
+	int gpu_freq, ia_freq, max_ia_freq;
+	int scaling_factor = 180;
+
+	max_ia_freq = cpufreq_quick_get_max(0);
+	/*
+	 * Default to measured freq if none found, PCU will ensure we don't go
+	 * over
+	 */
+	if (!max_ia_freq)
+		max_ia_freq = tsc_khz;
+
+	/* Convert from kHz to MHz */
+	max_ia_freq /= 1000;
+
+	mutex_lock(&dev_priv->dev->struct_mutex);
+
+	/*
+	 * For each potential GPU frequency, load a ring frequency we'd like
+	 * to use for memory access.  We do this by specifying the IA frequency
+	 * the PCU should use as a reference to determine the ring frequency.
+	 */
+	for (gpu_freq = dev_priv->max_delay; gpu_freq >= dev_priv->min_delay;
+	     gpu_freq--) {
+		int diff = dev_priv->max_delay - gpu_freq;
+
+		/*
+		 * For GPU frequencies less than 750MHz, just use the lowest
+		 * ring freq.
+		 */
+		if (gpu_freq < min_freq)
+			ia_freq = 800;
+		else
+			ia_freq = max_ia_freq - ((diff * scaling_factor) / 2);
+		ia_freq = DIV_ROUND_CLOSEST(ia_freq, 100);
+
+		I915_WRITE(GEN6_PCODE_DATA,
+			   (ia_freq << GEN6_PCODE_FREQ_IA_RATIO_SHIFT) |
+			   gpu_freq);
+		I915_WRITE(GEN6_PCODE_MAILBOX, GEN6_PCODE_READY |
+			   GEN6_PCODE_WRITE_MIN_FREQ_TABLE);
+		if (wait_for((I915_READ(GEN6_PCODE_MAILBOX) &
+			      GEN6_PCODE_READY) == 0, 10)) {
+			DRM_ERROR("pcode write of freq table timed out\n");
+			continue;
+		}
+	}
+
+	mutex_unlock(&dev_priv->dev->struct_mutex);
+}
+
 static void ironlake_init_clock_gating(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -7916,8 +7970,10 @@ void intel_modeset_init(struct drm_device *dev)
 		intel_init_emon(dev);
 	}
 
-	if (IS_GEN6(dev))
+	if (IS_GEN6(dev)) {
 		gen6_enable_rps(dev_priv);
+		gen6_update_ring_freq(dev_priv);
+	}
 
 	INIT_WORK(&dev_priv->idle_work, intel_idle_update);
 	setup_timer(&dev_priv->idle_timer, intel_gpu_idle_timer,

drivers/gpu/drm/i915/intel_drv.h

@@ -317,6 +317,7 @@ extern void intel_enable_clock_gating(struct drm_device *dev);
 extern void ironlake_enable_drps(struct drm_device *dev);
 extern void ironlake_disable_drps(struct drm_device *dev);
 extern void gen6_enable_rps(struct drm_i915_private *dev_priv);
+extern void gen6_update_ring_freq(struct drm_i915_private *dev_priv);
 extern void gen6_disable_rps(struct drm_device *dev);
 extern void intel_init_emon(struct drm_device *dev);