drm/i915: Disable DDR DVFS on CHV

DDR DVFS introduces massive memory latencies which can't be handled by
the PND deadline stuff. Instead the watermarks will need to be
programmed to compensate for the latency and the deadlines will need to
be programmed to tight fixed values. That means DDR DVFS can only be
enabled if the display FIFOs are large enough, and that pretty much
means we have to manually repartition them to suit the needs of the
moment.

That's a lot of change, so in the meantime let's just disable DDR DVFS
to get the display(s) to be stable.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index e90ec21dd9b2..0e84558c053a 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -263,6 +263,28 @@ static const struct cxsr_latency *intel_get_cxsr_latency(int is_desktop,
 	return NULL;
 }
 
+static void chv_set_memory_dvfs(struct drm_i915_private *dev_priv, bool enable)
+{
+	u32 val;
+
+	mutex_lock(&dev_priv->rps.hw_lock);
+
+	val = vlv_punit_read(dev_priv, PUNIT_REG_DDR_SETUP2);
+	if (enable)
+		val &= ~FORCE_DDR_HIGH_FREQ;
+	else
+		val |= FORCE_DDR_HIGH_FREQ;
+	val &= ~FORCE_DDR_LOW_FREQ;
+	val |= FORCE_DDR_FREQ_REQ_ACK;
+	vlv_punit_write(dev_priv, PUNIT_REG_DDR_SETUP2, val);
+
+	if (wait_for((vlv_punit_read(dev_priv, PUNIT_REG_DDR_SETUP2) &
+		      FORCE_DDR_FREQ_REQ_ACK) == 0, 3))
+		DRM_ERROR("timed out waiting for Punit DDR DVFS request\n");
+
+	mutex_unlock(&dev_priv->rps.hw_lock);
+}
+
 static void chv_set_memory_pm5(struct drm_i915_private *dev_priv, bool enable)
 {
 	u32 val;
@@ -310,6 +332,7 @@ void intel_set_memory_cxsr(struct drm_i915_private *dev_priv, bool enable)
 		      enable ? "enabled" : "disabled");
 }
 
+
 /*
  * Latency for FIFO fetches is dependent on several factors:
  *   - memory configuration (speed, channels)
@@ -1020,6 +1043,17 @@ static void valleyview_update_wm(struct drm_crtc *crtc)
 		      wm.pipe[pipe].primary, wm.pipe[pipe].cursor,
 		      wm.sr.plane, wm.sr.cursor);
 
+	/*
+	 * FIXME DDR DVFS introduces massive memory latencies which
+	 * are not known to system agent so any deadline specified
+	 * by the display may not be respected. To support DDR DVFS
+	 * the watermark code needs to be rewritten to essentially
+	 * bypass deadline mechanism and rely solely on the
+	 * watermarks. For now disable DDR DVFS.
+	 */
+	if (IS_CHERRYVIEW(dev_priv))
+		chv_set_memory_dvfs(dev_priv, false);
+
 	if (!cxsr_enabled)
 		intel_set_memory_cxsr(dev_priv, false);