drm/i915: Don't try to use the hardware frame counter with i965gm TV output

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 :(

v2: Move the zero vs. non-zero hw counter value handling
    into i915_get_vblank_counter() (Daniel)
    Use the per-crtc maximum exclusively, leaving the
    per-device maximum at zero
v3: max_vblank_count not populated yet in intel_enable_pipe()
    use intel_crtc_max_vblank_count() instead

Cc: stable@vger.kernel.org
Cc: Daniel Vetter <daniel@ffwll.ch>
Fixes: 51e31d49 ("drm/i915: Use generic vblank wait")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93782Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190122125149.GE5527@ideak-desk.fi.intel.comReviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/i915_irq.c

@@ -821,11 +821,26 @@ static void i915_enable_asle_pipestat(struct drm_i915_private *dev_priv)
 static u32 i915_get_vblank_counter(struct drm_device *dev, unsigned int pipe)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+	const struct drm_display_mode *mode = &vblank->hwmode;
 	i915_reg_t high_frame, low_frame;
 	u32 high1, high2, low, pixel, vbl_start, hsync_start, htotal;
-	const struct drm_display_mode *mode = &dev->vblank[pipe].hwmode;
 	unsigned long irqflags;
 
+	/*
+	 * On i965gm TV output the frame counter only works up to
+	 * the point when we enable the TV encoder. After that the
+	 * frame counter ceases to work and reads zero. We need a
+	 * vblank wait before enabling the TV encoder and so we
+	 * have to enable vblank interrupts while the frame counter
+	 * is still in a working state. However the core vblank code
+	 * does not like us returning non-zero frame counter values
+	 * when we've told it that we don't have a working frame
+	 * counter. Thus we must stop non-zero values leaking out.
+	 */
+	if (!vblank->max_vblank_count)
+		return 0;
+
 	htotal = mode->crtc_htotal;
 	hsync_start = mode->crtc_hsync_start;
 	vbl_start = mode->crtc_vblank_start;
@@ -4579,16 +4594,10 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 	if (INTEL_GEN(dev_priv) >= 8)
 		rps->pm_intrmsk_mbz |= GEN8_PMINTR_DISABLE_REDIRECT_TO_GUC;
 
-	if (IS_GEN(dev_priv, 2)) {
-		/* Gen2 doesn't have a hardware frame counter */
-		dev->max_vblank_count = 0;
-	} else if (IS_G4X(dev_priv) || INTEL_GEN(dev_priv) >= 5) {
-		dev->max_vblank_count = 0xffffffff; /* full 32 bit counter */
+	if (INTEL_GEN(dev_priv) >= 5 || IS_G4X(dev_priv))
 		dev->driver->get_vblank_counter = g4x_get_vblank_counter;
-	} else {
+	else if (INTEL_GEN(dev_priv) >= 3)
 		dev->driver->get_vblank_counter = i915_get_vblank_counter;
-		dev->max_vblank_count = 0xffffff; /* only 24 bits of frame count */
-	}
 
 	/*
 	 * Opt out of the vblank disable timer on everything except gen2.

drivers/gpu/drm/i915/intel_display.c

@@ -1758,6 +1758,35 @@ enum pipe intel_crtc_pch_transcoder(struct intel_crtc *crtc)
 		return crtc->pipe;
 }
 
+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);
+
+	/*
+	 * On i965gm the hardware frame counter reads
+	 * zero when the TV encoder is enabled :(
+	 */
+	if (IS_I965GM(dev_priv) &&
+	    (crtc_state->output_types & BIT(INTEL_OUTPUT_TVOUT)))
+		return 0;
+
+	if (INTEL_GEN(dev_priv) >= 5 || IS_G4X(dev_priv))
+		return 0xffffffff; /* full 32 bit counter */
+	else if (INTEL_GEN(dev_priv) >= 3)
+		return 0xffffff; /* only 24 bits of frame count */
+	else
+		return 0; /* Gen2 doesn't have a hardware frame counter */
+}
+
+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 intel_enable_pipe(const struct intel_crtc_state *new_crtc_state)
 {
 	struct intel_crtc *crtc = to_intel_crtc(new_crtc_state->base.crtc);
@@ -1810,7 +1839,7 @@ static void intel_enable_pipe(const struct intel_crtc_state *new_crtc_state)
 	 * when it's derived from the timestamps. So let's wait for the
 	 * pipe to start properly before we call drm_crtc_vblank_on()
 	 */
-	if (dev_priv->drm.max_vblank_count == 0)
+	if (intel_crtc_max_vblank_count(new_crtc_state) == 0)
 		intel_wait_for_pipe_scanline_moving(crtc);
 }
 
@@ -5678,7 +5707,7 @@ 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);
 
@@ -5832,7 +5861,7 @@ 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);
 
@@ -6171,7 +6200,7 @@ 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);
 }
@@ -6230,7 +6259,7 @@ 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);
 }
@@ -12778,8 +12807,9 @@ static int intel_atomic_prepare_commit(struct drm_device *dev,
 u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;
+	struct drm_vblank_crtc *vblank = &dev->vblank[drm_crtc_index(&crtc->base)];
 
-	if (!dev->max_vblank_count)
+	if (!vblank->max_vblank_count)
 		return (u32)drm_crtc_accurate_vblank_count(&crtc->base);
 
 	return dev->driver->get_vblank_counter(dev, crtc->pipe);
@@ -15894,10 +15924,12 @@ 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);