drm: Add get_scanout_position() to struct drm_crtc_helper_funcs

The new callback get_scanout_position() reads the current location
of the scanout process. The operation is currently located in struct
drm_driver, but really belongs to the CRTC. Drivers will be converted
in separate patches.

To help with the conversion, the timestamp calculation has been
moved from drm_calc_vbltimestamp_from_scanoutpos() to
drm_crtc_vblank_helper_get_vblank_timestamp_internal(). The helper
function supports the new and old interface of get_scanout_position().
drm_calc_vbltimestamp_from_scanoutpos() remains as a wrapper around
the new function.

Callback functions return the scanout position from the CRTC. The
legacy version of the interface receives the device and pipe index,
the modern version receives a pointer to the CRTC. We keep the
legacy version until all drivers have been converted.

v4:
	* 80-character line fixes
v3:
	* refactor drm_calc_vbltimestamp_from_scanoutpos() to minimize
	  code duplication
	* define types for get_scanout_position() callbacks
v2:
	* fix logical op in drm_calc_vbltimestamp_from_scanoutpos()

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Yannick Fertré <yannick.fertre@st.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200123135943.24140-3-tzimmermann@suse.de

3 files changed, 74 insertions, 5 deletions

diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 77685ed7aa65..8dd0d02647d3 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -362,11 +362,8 @@ struct drm_driver {
 	 * True on success, false if a reliable scanout position counter could
 	 * not be read out.
 	 *
-	 * FIXME:
-	 *
-	 * Since this is a helper to implement @get_vblank_timestamp, we should
-	 * move it to &struct drm_crtc_helper_funcs, like all the other
-	 * helper-internal hooks.
+	 * This is deprecated and should not be used by new drivers.
+	 * Use &drm_crtc_helper_funcs.get_scanout_position instead.
 	 */
 	bool (*get_scanout_position) (struct drm_device *dev, unsigned int pipe,
 				      bool in_vblank_irq, int *vpos, int *hpos,
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 5a87f1bd7a3f..e398512bfd5f 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -450,6 +450,53 @@ struct drm_crtc_helper_funcs {
 	 */
 	void (*atomic_disable)(struct drm_crtc *crtc,
 			       struct drm_crtc_state *old_crtc_state);
+
+	/**
+	 * @get_scanout_position:
+	 *
+	 * Called by vblank timestamping code.
+	 *
+	 * Returns the current display scanout position from a CRTC and an
+	 * optional accurate ktime_get() timestamp of when the position was
+	 * measured. Note that this is a helper callback which is only used
+	 * if a driver uses drm_calc_vbltimestamp_from_scanoutpos() for the
+	 * @drm_driver.get_vblank_timestamp callback.
+	 *
+	 * Parameters:
+	 *
+	 * crtc:
+	 *     The CRTC.
+	 * in_vblank_irq:
+	 *     True when called from drm_crtc_handle_vblank(). Some drivers
+	 *     need to apply some workarounds for gpu-specific vblank irq
+	 *     quirks if the flag is set.
+	 * vpos:
+	 *     Target location for current vertical scanout position.
+	 * hpos:
+	 *     Target location for current horizontal scanout position.
+	 * stime:
+	 *     Target location for timestamp taken immediately before
+	 *     scanout position query. Can be NULL to skip timestamp.
+	 * etime:
+	 *     Target location for timestamp taken immediately after
+	 *     scanout position query. Can be NULL to skip timestamp.
+	 * mode:
+	 *     Current display timings.
+	 *
+	 * Returns vpos as a positive number while in active scanout area.
+	 * Returns vpos as a negative number inside vblank, counting the number
+	 * of scanlines to go until end of vblank, e.g., -1 means "one scanline
+	 * until start of active scanout / end of vblank."
+	 *
+	 * Returns:
+	 *
+	 * True on success, false if a reliable scanout position counter could
+	 * not be read out.
+	 */
+	bool (*get_scanout_position)(struct drm_crtc *crtc,
+				     bool in_vblank_irq, int *vpos, int *hpos,
+				     ktime_t *stime, ktime_t *etime,
+				     const struct drm_display_mode *mode);
 };
 
 /**
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 94275e93fd27..fd28741e64ed 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -239,4 +239,29 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc);
 void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
 				   u32 max_vblank_count);
+
+typedef bool (*drm_vblank_get_scanout_position_func)(struct drm_crtc *crtc,
+						     bool in_vblank_irq,
+						     int *vpos, int *hpos,
+						     ktime_t *stime,
+						     ktime_t *etime,
+						     const struct drm_display_mode *mode);
+
+typedef bool (*drm_vblank_get_scanout_position_legacy_func)(struct drm_device *dev,
+							    unsigned int pipe,
+							    bool in_vblank_irq,
+							    int *vpos,
+							    int *hpos,
+							    ktime_t *stime,
+							    ktime_t *etime,
+							    const struct drm_display_mode *mode);
+
+bool
+drm_crtc_vblank_helper_get_vblank_timestamp_internal(struct drm_crtc *crtc,
+						     int *max_error,
+						     ktime_t *vblank_time,
+						     bool in_vblank_irq,
+						     drm_vblank_get_scanout_position_func get_scanout_position,
+						     drm_vblank_get_scanout_position_legacy_func get_scanout_position_legacy);
+
 #endif