drm/i915: Disallow plane x+w>stride on ilk+ with X-tiling

ilk+ planes get notably unhappy when the plane x+w exceeds
the stride. This wasn't a problem previously because we
always aligned SURF to the closest tile boundary so the
x offset never got particularly large. But now with async
flips we have to align to 256KiB instead and thus this
becomes a real issue.

On ilk/snb/ivb it looks like the accesses just wrap
early to the next tile row when scanout goes past the
SURF+n*stride boundary, hsw/bdw suffer more heavily and
start to underrun constantly. i965/g4x appear to be immune.
vlv/chv I've not yet checked.

Let's borrow another trick from the skl+ code and search
backwards for a better SURF offset in the hopes of getting the
x offset below the limit. IIRC when I ran into a similar issue
on skl years ago it was causing the hardware to fall over
pretty hard as well.

And let's be consistent and include i965/g4x in the check
as well, just in case I just got super lucky somehow when
I wasn't able to reproduce the issue. Not that it really
matters since we still use 4k SURF alignment for i965/g4x
anyway.

Fixes: 6ede6b06 ("drm/i915: Implement async flips for vlv/chv")
Fixes: 4bb18054 ("drm/i915: Implement async flip for ilk/snb")
Fixes: 2a636e24 ("drm/i915: Implement async flip for ivb/hsw")
Fixes: cda195f1 ("drm/i915: Implement async flips for bdw")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210209021918.16234-1-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit 59fb8218)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
[Rodrigo also exported some functions from intel_display.c during backport]

drivers/gpu/drm/i915/display/i9xx_plane.c

@@ -255,6 +255,33 @@ int i9xx_check_plane_surface(struct intel_plane_state *plane_state)
 	else
 		offset = 0;
 
+	/*
+	 * When using an X-tiled surface the plane starts to
+	 * misbehave if the x offset + width exceeds the stride.
+	 * hsw/bdw: underrun galore
+	 * ilk/snb/ivb: wrap to the next tile row mid scanout
+	 * i965/g4x: so far appear immune to this
+	 * vlv/chv: TODO check
+	 *
+	 * Linear surfaces seem to work just fine, even on hsw/bdw
+	 * despite them not using the linear offset anymore.
+	 */
+	if (INTEL_GEN(dev_priv) >= 4 && fb->modifier == I915_FORMAT_MOD_X_TILED) {
+		u32 alignment = intel_surf_alignment(fb, 0);
+		int cpp = fb->format->cpp[0];
+
+		while ((src_x + src_w) * cpp > plane_state->color_plane[0].stride) {
+			if (offset == 0) {
+				drm_dbg_kms(&dev_priv->drm,
+					    "Unable to find suitable display surface offset due to X-tiling\n");
+				return -EINVAL;
+			}
+
+			offset = intel_plane_adjust_aligned_offset(&src_x, &src_y, plane_state, 0,
+								   offset, offset - alignment);
+		}
+	}
+
 	/*
 	 * Put the final coordinates back so that the src
 	 * coordinate checks will see the right values.

drivers/gpu/drm/i915/display/intel_display.c

@@ -1322,8 +1322,8 @@ static bool has_async_flips(struct drm_i915_private *i915)
 	return INTEL_GEN(i915) >= 5;
 }
 
-static unsigned int intel_surf_alignment(const struct drm_framebuffer *fb,
-					 int color_plane)
+unsigned int intel_surf_alignment(const struct drm_framebuffer *fb,
+				  int color_plane)
 {
 	struct drm_i915_private *dev_priv = to_i915(fb->dev);
 
@@ -1590,10 +1590,10 @@ static u32 intel_adjust_aligned_offset(int *x, int *y,
  * Adjust the tile offset by moving the difference into
  * the x/y offsets.
  */
-static u32 intel_plane_adjust_aligned_offset(int *x, int *y,
-					     const struct intel_plane_state *state,
-					     int color_plane,
-					     u32 old_offset, u32 new_offset)
+u32 intel_plane_adjust_aligned_offset(int *x, int *y,
+				      const struct intel_plane_state *state,
+				      int color_plane,
+				      u32 old_offset, u32 new_offset)
 {
 	return intel_adjust_aligned_offset(x, y, state->hw.fb, color_plane,
 					   state->hw.rotation,

drivers/gpu/drm/i915/display/intel_display.h

@@ -653,6 +653,12 @@ void intel_plane_unpin_fb(struct intel_plane_state *old_plane_state);
 struct intel_encoder *
 intel_get_crtc_new_encoder(const struct intel_atomic_state *state,
 			   const struct intel_crtc_state *crtc_state);
+unsigned int intel_surf_alignment(const struct drm_framebuffer *fb,
+				  int color_plane);
+u32 intel_plane_adjust_aligned_offset(int *x, int *y,
+				      const struct intel_plane_state *state,
+				      int color_plane,
+				      u32 old_offset, u32 new_offset);
 
 /* modesetting */
 void intel_modeset_init_hw(struct drm_i915_private *i915);