drm/vblank: drop the mode argument from drm_calc_vbltimestamp_from_scanoutpos

If we restrict this helper to only kms drivers (which is the case) we
can look up the correct mode easily ourselves. But it's a bit tricky:

- All legacy drivers look at crtc->hwmode. But that is updated already
  at the beginning of the modeset helper, which means when we disable
  a pipe. Hence the final timestamps might be a bit off. But since
  this is an existing bug I'm not going to change it, but just try to
  be bug-for-bug compatible with the current code. This only applies
  to radeon&amdgpu.

- i915 tries to get it perfect by updating crtc->hwmode when the pipe
  is off (i.e. vblank->enabled = false).

- All other atomic drivers look at crtc->state->adjusted_mode. Those
  that look at state->requested_mode simply don't adjust their mode,
  so it's the same. That has two problems: Accessing crtc->state from
  interrupt handling code is unsafe, and it's updated before we shut
  down the pipe. For nonblocking modesets it's even worse.

For atomic drivers try to implement what i915 does. To do that we add
a new hwmode field to the vblank structure, and update it from
drm_calc_timestamping_constants(). For atomic drivers that's called
from the right spot by the helper library already, so all fine. But
for safety let's enforce that.

For legacy driver this function is only called at the end (oh the
fun), which is broken, so again let's not bother and just stay
bug-for-bug compatible.

The  benefit is that we can use drm_calc_vbltimestamp_from_scanoutpos
directly to implement ->get_vblank_timestamp in every driver, deleting
a lot of code.

v2: Completely new approach, trying to mimick the i915 solution.

v3: Fixup kerneldoc.

v4: Drop the WARN_ON to check that the vblank is off, atomic helpers
currently unconditionally call this. Recomputing the same stuff should
be harmless.

v5: Fix typos and move misplaced hunks to the right patches (Neil).

v6: Undo hunk movement (kbuild).

Cc: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
Cc: Eric Anholt <eric@anholt.net>
Cc: Rob Clark <robdclark@gmail.com>
Cc: linux-arm-msm@vger.kernel.org
Cc: freedreno@lists.freedesktop.org
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170509140329.24114-4-daniel.vetter@ffwll.ch

1 files changed, 31 insertions, 12 deletions

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index fba6a842f4cd..89f0928b042a 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -684,6 +684,7 @@ void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 
 	vblank->linedur_ns  = linedur_ns;
 	vblank->framedur_ns = framedur_ns;
+	vblank->hwmode = *mode;
 
 	DRM_DEBUG("crtc %u: hwmode: htotal %d, vtotal %d, vdisplay %d\n",
 		  crtc->base.id, mode->crtc_htotal,
@@ -704,7 +705,6 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
  *     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.
- * @mode: mode which defines the scanout timings
  *
  * Implements calculation of exact vblank timestamps from given drm_display_mode
  * timings and current video scanout position of a CRTC. This can be called from
@@ -724,6 +724,13 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants);
  * returns as no operation if a doublescan or interlaced video mode is
  * active. Higher level code is expected to handle this.
  *
+ * This function can be used to implement the &drm_driver.get_vblank_timestamp
+ * directly, if the driver implements the &drm_driver.get_scanout_position hook.
+ *
+ * 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
@@ -733,17 +740,23 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 					   unsigned int pipe,
 					   int *max_error,
 					   struct timeval *vblank_time,
-					   bool in_vblank_irq,
-					   const struct drm_display_mode *mode)
+					   bool in_vblank_irq)
 {
 	struct timeval tv_etime;
 	ktime_t stime, etime;
-	unsigned int vbl_status;
+	bool vbl_status;
+	struct drm_crtc *crtc;
+	const struct drm_display_mode *mode;
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
 	int vpos, hpos, i;
 	int delta_ns, duration_ns;
-	unsigned flags = in_vblank_irq ? DRM_CALLED_FROM_VBLIRQ : 0;
 
-	if (pipe >= dev->num_crtcs) {
+	if (!drm_core_check_feature(dev, DRIVER_MODESET))
+		return false;
+
+	crtc = drm_crtc_from_index(dev, pipe);
+
+	if (pipe >= dev->num_crtcs || !crtc) {
 		DRM_ERROR("Invalid crtc %u\n", pipe);
 		return false;
 	}
@@ -754,6 +767,11 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 		return false;
 	}
 
+	if (drm_drv_uses_atomic_modeset(dev))
+		mode = &vblank->hwmode;
+	else
+		mode = &crtc->hwmode;
+
 	/* If mode timing undefined, just return as no-op:
 	 * Happens during initial modesetting of a crtc.
 	 */
@@ -774,15 +792,16 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 		 * Get vertical and horizontal scanout position vpos, hpos,
 		 * and bounding timestamps stime, etime, pre/post query.
 		 */
-		vbl_status = dev->driver->get_scanout_position(dev, pipe, flags,
+		vbl_status = dev->driver->get_scanout_position(dev, pipe,
+							       in_vblank_irq,
 							       &vpos, &hpos,
 							       &stime, &etime,
 							       mode);
 
 		/* Return as no-op if scanout query unsupported or failed. */
-		if (!(vbl_status & DRM_SCANOUTPOS_VALID)) {
-			DRM_DEBUG("crtc %u : scanoutpos query failed [0x%x].\n",
-				  pipe, vbl_status);
+		if (!vbl_status) {
+			DRM_DEBUG("crtc %u : scanoutpos query failed.\n",
+				  pipe);
 			return false;
 		}
 
@@ -821,8 +840,8 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 	etime = ktime_sub_ns(etime, delta_ns);
 	*vblank_time = ktime_to_timeval(etime);
 
-	DRM_DEBUG_VBL("crtc %u : v 0x%x p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",
-		      pipe, vbl_status, hpos, vpos,
+	DRM_DEBUG_VBL("crtc %u : v p(%d,%d)@ %ld.%ld -> %ld.%ld [e %d us, %d rep]\n",
+		      pipe, hpos, vpos,
 		      (long)tv_etime.tv_sec, (long)tv_etime.tv_usec,
 		      (long)vblank_time->tv_sec, (long)vblank_time->tv_usec,
 		      duration_ns/1000, i);