[PATCH 02/15] drm/i915: Don't try to use the hardware frame counter with i965gm TV output

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

On i965gm the hardware frame counter does not work when
the TV encoder is active. So let's not try to consult
the hardware frame counter in that case. Instead we'll
fall back to the timestamp based guesstimation method
used on gen2.

Note that the pipe timings generated by the TV encoder
are also rather peculiar. Apparently the pipe wants to
run at a much higher speed (related to the oversample
clock somehow it seems) but during the vertical active
period the TV encoder stalls the pipe every few lines
to keep its speed in check. But once the vertical
blanking period is reached the pipe gets to run at full
speed. This means our vblank timestamp estimates are
suspect. Fixing all that would require quite a bit
more work. This simple fix at least avoids the nasty
vblank timeouts that are happening currently.

Curiously the frame counter works just fine on i945gm
and gm45. I don't really understand what kind of mishap
occurred with the hardware design on i965gm. Sadly
I wasn't able to find any chicken bits etc. that would
fix the frame counter :(

Cc: stable at vger.kernel.org
Fixes: 51e31d49c890 ("drm/i915: Use generic vblank wait")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93782
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c      | 10 ++++++-
 drivers/gpu/drm/i915/intel_display.c | 40 +++++++++++++++++++++++-----
 2 files changed, 43 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index d447d7d508f4..019cb685986c 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -4843,8 +4843,16 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 		dev->max_vblank_count = 0xffffffff; /* full 32 bit counter */
 		dev->driver->get_vblank_counter = g4x_get_vblank_counter;
 	} else {
+		/*
+		 * On i965gm the hardware frame counter reads zero
+		 * when the TV encoder is used. Hence we configure
+		 * max_vblank_count dynamically for each crtc.
+		 */
+		if (IS_I965GM(dev_priv))
+			dev->max_vblank_count = 0;
+		else
+			dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
 		dev->driver->get_vblank_counter = i915_get_vblank_counter;
-		dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
 	}
 
 	/*
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 940577f8c041..2dccb3310ad2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5504,6 +5504,32 @@ static void intel_encoders_post_pll_disable(struct drm_crtc *crtc,
 	}
 }
 
+static u32 intel_crtc_max_vblank_count(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
+	u32 max_vblank_count = dev_priv->drm.max_vblank_count;
+
+	/*
+	 * On i965gm the hardware frame counter always
+	 * reads zero when the TV encoder is used :(
+	 * Otherwise we get the 24 bit frame counter.
+	 */
+	if (IS_I965GM(dev_priv) &&
+	    (crtc_state->output_types & BIT(INTEL_OUTPUT_TVOUT)) == 0)
+		max_vblank_count = 0xffffff; /* only 24 bits of frame count */
+
+	return max_vblank_count;
+}
+
+static void intel_crtc_vblank_on(const struct intel_crtc_state *crtc_state)
+{
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->base.crtc);
+
+	drm_crtc_set_max_vblank_count(&crtc->base,
+				      intel_crtc_max_vblank_count(crtc_state));
+	drm_crtc_vblank_on(&crtc->base);
+}
+
 static void ironlake_crtc_enable(struct intel_crtc_state *pipe_config,
 				 struct drm_atomic_state *old_state)
 {
@@ -5577,7 +5603,7 @@ static void ironlake_crtc_enable(struct intel_crtc_state *pipe_config,
 		ironlake_pch_enable(old_intel_state, pipe_config);
 
 	assert_vblank_disabled(crtc);
-	drm_crtc_vblank_on(crtc);
+	intel_crtc_vblank_on(pipe_config);
 
 	intel_encoders_enable(crtc, pipe_config, old_state);
 
@@ -5734,7 +5760,7 @@ static void haswell_crtc_enable(struct intel_crtc_state *pipe_config,
 		intel_ddi_set_vc_payload_alloc(pipe_config, true);
 
 	assert_vblank_disabled(crtc);
-	drm_crtc_vblank_on(crtc);
+	intel_crtc_vblank_on(pipe_config);
 
 	intel_encoders_enable(crtc, pipe_config, old_state);
 
@@ -6074,7 +6100,7 @@ static void valleyview_crtc_enable(struct intel_crtc_state *pipe_config,
 	intel_enable_pipe(pipe_config);
 
 	assert_vblank_disabled(crtc);
-	drm_crtc_vblank_on(crtc);
+	intel_crtc_vblank_on(pipe_config);
 
 	intel_encoders_enable(crtc, pipe_config, old_state);
 }
@@ -6133,7 +6159,7 @@ static void i9xx_crtc_enable(struct intel_crtc_state *pipe_config,
 	intel_enable_pipe(pipe_config);
 
 	assert_vblank_disabled(crtc);
-	drm_crtc_vblank_on(crtc);
+	intel_crtc_vblank_on(pipe_config);
 
 	intel_encoders_enable(crtc, pipe_config, old_state);
 }
@@ -15752,10 +15778,12 @@ intel_modeset_setup_hw_state(struct drm_device *dev,
 	 * waits, so we need vblank interrupts restored beforehand.
 	 */
 	for_each_intel_crtc(&dev_priv->drm, crtc) {
+		crtc_state = to_intel_crtc_state(crtc->base.state);
+
 		drm_crtc_vblank_reset(&crtc->base);
 
-		if (crtc->base.state->active)
-			drm_crtc_vblank_on(&crtc->base);
+		if (crtc_state->base.active)
+			intel_crtc_vblank_on(crtc_state);
 	}
 
 	intel_sanitize_plane_mapping(dev_priv);
-- 
2.18.1