drm: Add get_vblank_timestamp() to struct drm_crtc_funcs

The callback get_vblank_timestamp() is currently located in struct
drm_driver, but really belongs into struct drm_crtc_funcs. Add an
equivalent there. Driver will be converted in separate patches.

The default implementation is drm_calc_vbltimestamp_from_scanoutpos().
The patch adds drm_crtc_vblank_helper_get_vblank_timestamp(), which is
an implementation for the CRTC callback.

v4:
* more readable code for setting high_prec (Ville, Jani)
v3:
* use refactored timestamp calculation to minimize duplicated code
* do more checks for crtc != NULL to support legacy drivers
v2:
* rename helper to drm_crtc_vblank_helper_get_vblank_timestamp()
* replace drm_calc_vbltimestamp_from_scanoutpos() with
drm_crtc_vblank_helper_get_vblank_timestamp() in docs

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Ville Syrjälä <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_vblank.c

···
 	u64 vblank;
 	unsigned long flags;
 
-	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) && !dev->driver->get_vblank_timestamp,
+	WARN_ONCE(drm_debug_enabled(DRM_UT_VBL) &&
+		  !crtc->funcs->get_vblank_timestamp &&
+		  !dev->driver->get_vblank_timestamp,
 		  "This function requires support for accurate vblank timestamps.");
 
 	spin_lock_irqsave(&dev->vblank_time_lock, flags);
···
  *
  * Calculate and store various constants which are later needed by vblank and
  * swap-completion timestamping, e.g, by
- * drm_calc_vbltimestamp_from_scanoutpos(). They are derived from CRTC's true
- * scanout timing, so they take things like panel scaling or other adjustments
- * into account.
+ * drm_crtc_vblank_helper_get_vblank_timestamp(). They are derived from
+ * CRTC's true scanout timing, so they take things like panel scaling or
+ * other adjustments into account.
  */
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode)
···
  *
  * Implements calculation of exact vblank timestamps from given drm_display_mode
  * timings and current video scanout position of a CRTC. This can be directly
- * used as the &drm_driver.get_vblank_timestamp implementation of a kms driver
- * if &drm_crtc_helper_funcs.get_scanout_position is implemented.
+ * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
+ * driver if &drm_crtc_helper_funcs.get_scanout_position or
+ * &drm_driver.get_scanout_position is implemented.
  *
  * The current implementation only handles standard video modes. For double scan
  * and interlaced modes the driver is supposed to adjust the hardware mode
···
 EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_internal);
 
 /**
+ * drm_crtc_vblank_helper_get_vblank_timestamp - precise vblank timestamp
+ *                                               helper
+ * @crtc: CRTC whose vblank timestamp to retrieve
+ * @max_error: Desired maximum allowable error in timestamps (nanosecs)
+ *             On return contains true maximum error of timestamp
+ * @vblank_time: Pointer to time which should receive the timestamp
+ * @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 flag is set.
+ *
+ * Implements calculation of exact vblank timestamps from given drm_display_mode
+ * timings and current video scanout position of a CRTC. This can be directly
+ * used as the &drm_crtc_funcs.get_vblank_timestamp implementation of a kms
+ * driver if &drm_crtc_helper_funcs.get_scanout_position is implemented.
+ *
+ * The current implementation only handles standard video modes. For double scan
+ * and interlaced modes the driver is supposed to adjust the hardware mode
+ * (taken from &drm_crtc_state.adjusted mode for atomic modeset drivers) to
+ * match the scanout position reported.
+ *
+ * Note that atomic drivers must call drm_calc_timestamping_constants() before
+ * enabling a CRTC. The atomic helpers already take care of that in
+ * drm_atomic_helper_update_legacy_modeset_state().
+ *
+ * Returns:
+ *
+ * Returns true on success, and false on failure, i.e. when no accurate
+ * timestamp could be acquired.
+ */
+bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
+						 int *max_error,
+						 ktime_t *vblank_time,
+						 bool in_vblank_irq)
+{
+	return drm_crtc_vblank_helper_get_vblank_timestamp_internal(
+		crtc, max_error, vblank_time, in_vblank_irq,
+		crtc->helper_private->get_scanout_position, NULL);
+}
+EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);
+
+/**
  * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
  *                             vblank interval
  * @dev: DRM device
···
 drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
 			  ktime_t *tvblank, bool in_vblank_irq)
 {
+	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
 	bool ret = false;
 
 	/* Define requested maximum error on timestamps (nanoseconds). */
 	int max_error = (int) drm_timestamp_precision * 1000;
 
 	/* Query driver if possible and precision timestamping enabled. */
-	if (dev->driver->get_vblank_timestamp && (max_error > 0))
+	if (crtc && crtc->funcs->get_vblank_timestamp && max_error > 0) {
+		struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+
+		ret = crtc->funcs->get_vblank_timestamp(crtc, &max_error,
+							tvblank, in_vblank_irq);
+	} else if (dev->driver->get_vblank_timestamp && max_error > 0) {
 		ret = dev->driver->get_vblank_timestamp(dev, pipe, &max_error,
 							tvblank, in_vblank_irq);
+	}
 
 	/* GPU high precision timestamp query unsupported or failed.
 	 * Return current monotonic/gettimeofday timestamp as best estimate.
···
 
 static void drm_handle_vblank_events(struct drm_device *dev, unsigned int pipe)
 {
+	struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+	bool high_prec = false;
 	struct drm_pending_vblank_event *e, *t;
 	ktime_t now;
 	u64 seq;
···
 		send_vblank_event(dev, e, seq, now);
 	}
 
-	trace_drm_vblank_event(pipe, seq, now,
-			dev->driver->get_vblank_timestamp != NULL);
+	if (crtc && crtc->funcs->get_vblank_timestamp)
+		high_prec = true;
+	else if (dev->driver->get_vblank_timestamp)
+		high_prec = true;
+
+	trace_drm_vblank_event(pipe, seq, now, high_prec);
 }
 
 /**

include/drm/drm_crtc.h

···
 	 * new drivers as the replacement of &drm_driver.disable_vblank hook.
 	 */
 	void (*disable_vblank)(struct drm_crtc *crtc);
+
+	/**
+	 * @get_vblank_timestamp:
+	 *
+	 * Called by drm_get_last_vbltimestamp(). Should return a precise
+	 * timestamp when the most recent vblank interval ended or will end.
+	 *
+	 * Specifically, the timestamp in @vblank_time should correspond as
+	 * closely as possible to the time when the first video scanline of
+	 * the video frame after the end of vblank will start scanning out,
+	 * the time immediately after end of the vblank interval. If the
+	 * @crtc is currently inside vblank, this will be a time in the future.
+	 * If the @crtc is currently scanning out a frame, this will be the
+	 * past start time of the current scanout. This is meant to adhere
+	 * to the OpenML OML_sync_control extension specification.
+	 *
+	 * Parameters:
+	 *
+	 * crtc:
+	 *     CRTC for which timestamp should be returned.
+	 * max_error:
+	 *     Maximum allowable timestamp error in nanoseconds.
+	 *     Implementation should strive to provide timestamp
+	 *     with an error of at most max_error nanoseconds.
+	 *     Returns true upper bound on error for timestamp.
+	 * vblank_time:
+	 *     Target location for returned vblank timestamp.
+	 * 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 flag is set.
+	 *
+	 * Returns:
+	 *
+	 * True on success, false on failure, which means the core should
+	 * fallback to a simple timestamp taken in drm_crtc_handle_vblank().
+	 */
+	bool (*get_vblank_timestamp)(struct drm_crtc *crtc,
+				     int *max_error,
+				     ktime_t *vblank_time,
+				     bool in_vblank_irq);
 };
 
 /**
···
 	 * Programmed mode in hw, after adjustments for encoders, crtc, panel
 	 * scaling etc. Should only be used by legacy drivers, for high
 	 * precision vblank timestamps in
-	 * drm_calc_vbltimestamp_from_scanoutpos().
+	 * drm_crtc_vblank_helper_get_vblank_timestamp().
 	 *
 	 * Note that atomic drivers should not use this, but instead use
 	 * &drm_crtc_state.adjusted_mode. And for high-precision timestamps
-	 * drm_calc_vbltimestamp_from_scanoutpos() used &drm_vblank_crtc.hwmode,
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() used
+	 * &drm_vblank_crtc.hwmode,
 	 * which is filled out by calling drm_calc_timestamping_constants().
 	 */
 	struct drm_display_mode hwmode;

include/drm/drm_modeset_helper_vtables.h

···
 	 * 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.
+	 * if a driver uses drm_crtc_vblank_helper_get_vblank_timestamp()
+	 * for the @drm_crtc_funcs.get_vblank_timestamp callback.
 	 *
 	 * Parameters:
 	 *

include/drm/drm_vblank.h

···
 	unsigned int pipe;
 	/**
 	 * @framedur_ns: Frame/Field duration in ns, used by
-	 * drm_calc_vbltimestamp_from_scanoutpos() and computed by
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() and computed by
 	 * drm_calc_timestamping_constants().
 	 */
 	int framedur_ns;
 	/**
 	 * @linedur_ns: Line duration in ns, used by
-	 * drm_calc_vbltimestamp_from_scanoutpos() and computed by
+	 * drm_crtc_vblank_helper_get_vblank_timestamp() and computed by
 	 * drm_calc_timestamping_constants().
 	 */
 	int linedur_ns;
···
 	 *
 	 * Cache of the current hardware display mode. Only valid when @enabled
 	 * is set. This is used by helpers like
-	 * drm_calc_vbltimestamp_from_scanoutpos(). We can't just access the
-	 * hardware mode by e.g. looking at &drm_crtc_state.adjusted_mode,
+	 * drm_crtc_vblank_helper_get_vblank_timestamp(). We can't just access
+	 * the hardware mode by e.g. looking at &drm_crtc_state.adjusted_mode,
 	 * because that one is really hard to get from interrupt context.
 	 */
 	struct drm_display_mode hwmode;
···
 void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
 				   u32 max_vblank_count);
 
+/*
+ * Helpers for struct drm_crtc_funcs
+ */
+
 typedef bool (*drm_vblank_get_scanout_position_func)(struct drm_crtc *crtc,
 						     bool in_vblank_irq,
 						     int *vpos, int *hpos,
···
 						     bool in_vblank_irq,
 						     drm_vblank_get_scanout_position_func get_scanout_position,
 						     drm_vblank_get_scanout_position_legacy_func get_scanout_position_legacy);
+bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
+						 int *max_error,
+						 ktime_t *vblank_time,
+						 bool in_vblank_irq);
 
 #endif