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>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e58627f..804ac4d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/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 @@
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 @@
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,