drm/tegra: dc: Add missing call to drm_vblank_on()

When the CRTC is enabled, make sure the VBLANK machinery is enabled.
Failure to do so will cause drm_vblank_get() to not enable the VBLANK on
the CRTC and VBLANK-synchronized page-flips won't work.

While at it, get rid of the legacy drm_vblank_pre_modeset() and
drm_vblank_post_modeset() calls that are replaced by drm_vblank_on()
and drm_vblank_off().

Reported-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dc.c

@@ -736,7 +736,6 @@ static const struct drm_crtc_funcs tegra_crtc_funcs = {
 
 static void tegra_crtc_disable(struct drm_crtc *crtc)
 {
-	struct tegra_dc *dc = to_tegra_dc(crtc);
 	struct drm_device *drm = crtc->dev;
 	struct drm_plane *plane;
 
@@ -752,7 +751,7 @@ static void tegra_crtc_disable(struct drm_crtc *crtc)
 		}
 	}
 
-	drm_vblank_off(drm, dc->pipe);
+	drm_crtc_vblank_off(crtc);
 }
 
 static bool tegra_crtc_mode_fixup(struct drm_crtc *crtc,
@@ -841,8 +840,6 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc,
 	u32 value;
 	int err;
 
-	drm_vblank_pre_modeset(crtc->dev, dc->pipe);
-
 	err = tegra_crtc_setup_clk(crtc, mode);
 	if (err) {
 		dev_err(dc->dev, "failed to setup clock for CRTC: %d\n", err);
@@ -896,6 +893,8 @@ static void tegra_crtc_prepare(struct drm_crtc *crtc)
 	unsigned int syncpt;
 	unsigned long value;
 
+	drm_crtc_vblank_off(crtc);
+
 	/* hardware initialization */
 	reset_control_deassert(dc->rst);
 	usleep_range(10000, 20000);
@@ -943,7 +942,7 @@ static void tegra_crtc_commit(struct drm_crtc *crtc)
 	value = GENERAL_ACT_REQ | WIN_A_ACT_REQ;
 	tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL);
 
-	drm_vblank_post_modeset(crtc->dev, dc->pipe);
+	drm_crtc_vblank_on(crtc);
 }
 
 static void tegra_crtc_load_lut(struct drm_crtc *crtc)