[Intel-gfx] [V14 5/5] drm/i915/dsi: Enable software vblank counter

[Vandita Kulkarni]

In case of DSI cmd mode, we get hw vblank counter
updated after the TE comes in, if we try to read
the hw vblank counter in te handler we wouldnt have
the udpated vblank counter yet.
This will lead to a state where we would send the
vblank event to the user space in the next te,
though the frame update would have completed in
the first TE duration itself.
Hence switch to using software timestamp based
vblank counter.

v2: Use mode_flags from crtc_state (Ville)

Signed-off-by: Vandita Kulkarni <vandita.kulkarni at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 11 +++++++++++
 drivers/gpu/drm/i915/i915_irq.c              |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 5a9d933e425a..bb495947ccd5 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -1808,6 +1808,17 @@ enum pipe intel_crtc_pch_transcoder(struct intel_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->uapi.crtc->dev);
+	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
+	u32 mode_flags = crtc->mode_flags;
+
+	/*
+	 * From Gen 11, In case of dsi cmd mode, frame counter wouldnt
+	 * have updated at the beginning of TE, if we want to use
+	 * the hw counter, then we would find it updated in only
+	 * the next TE, hence switching to sw counter.
+	 */
+	if (mode_flags & (I915_MODE_FLAG_DSI_USE_TE0 | I915_MODE_FLAG_DSI_USE_TE1))
+		return 0;
 
 	/*
 	 * On i965gm the hardware frame counter reads
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index c2e4b227bdf3..634c60befe7e 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -682,8 +682,12 @@ u32 i915_get_vblank_counter(struct drm_crtc *crtc)
 u32 g4x_get_vblank_counter(struct drm_crtc *crtc)
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
+	struct drm_vblank_crtc *vblank = &dev_priv->drm.vblank[drm_crtc_index(crtc)];
 	enum pipe pipe = to_intel_crtc(crtc)->pipe;
 
+	if (!vblank->max_vblank_count)
+		return 0;
+
 	return I915_READ(PIPE_FRMCOUNT_G4X(pipe));
 }
 
-- 
2.21.0.5.gaeb582a