[Intel-gfx] [PATCH 2/7] drm/i915/tgl: Make sure a semiplanar UV plane is tile row size aligned

[Imre Deak]

Currently the GGTT offset of a UV plane in a semiplanar YUV FB is tile
size (4kB) aligned. I noticed, that enforcing only this alignment leads
oddly to random memory corruptions on TGL while scanning out Y-tiled
FBs. This issue can be easily reproduced with a UV plane offset that is
not aligned to the plane's tile row size.

Some experiments showed the correct alignment to be tile row size
indeed. This also makes sense, since the de-tiling fence created for the
object - with its own stride and so "left" and "right" edge - applies to
all the planes in the FB, so each tile row of all planes should be tile
row aligned.

In fact BSpec requires this alignment since SKL. On SKL we may enforce
this due to the AUX plane x,y coords check, but on ICL and TGL we don't.
For now enforce this only on TGL; I can follow up with any necessary
change for ICL after more tests.

BSpec requires a stricter alignment for linear UV planes too (kind of a
tile row alignment), but it's unclear whether that's really needed
(couldn't be explained with the de-tiling fence as above) and enforcing
that could break existing user space; so avoid that too for now until
more tests.

v2:
- Clarify the commit log wrt. the address space the alignment applies to.
  (Chris)

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Imre Deak <imre.deak at intel.com>
Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/display/intel_display.c | 36 ++++++++++++++++++--
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 6e4152770c15..bbc9cf288067 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -1995,6 +1995,13 @@ intel_format_info_is_yuv_semiplanar(const struct drm_format_info *info,
 	       info->num_planes == (is_ccs_modifier(modifier) ? 4 : 2);
 }
 
+static bool is_semiplanar_uv_plane(const struct drm_framebuffer *fb,
+				   int color_plane)
+{
+	return intel_format_info_is_yuv_semiplanar(fb->format, fb->modifier) &&
+	       color_plane == 1;
+}
+
 static unsigned int
 intel_tile_width_bytes(const struct drm_framebuffer *fb, int color_plane)
 {
@@ -2069,6 +2076,16 @@ static void intel_tile_dims(const struct drm_framebuffer *fb, int color_plane,
 	*tile_height = intel_tile_height(fb, color_plane);
 }
 
+static unsigned int intel_tile_row_size(const struct drm_framebuffer *fb,
+					int color_plane)
+{
+	unsigned int tile_width, tile_height;
+
+	intel_tile_dims(fb, color_plane, &tile_width, &tile_height);
+
+	return fb->pitches[color_plane] * tile_height;
+}
+
 unsigned int
 intel_fb_align_height(const struct drm_framebuffer *fb,
 		      int color_plane, unsigned int height)
@@ -2143,7 +2160,8 @@ static unsigned int intel_surf_alignment(const struct drm_framebuffer *fb,
 	struct drm_i915_private *dev_priv = to_i915(fb->dev);
 
 	/* AUX_DIST needs only 4K alignment */
-	if (is_aux_plane(fb, color_plane))
+	if ((INTEL_GEN(dev_priv) < 12 && is_aux_plane(fb, color_plane)) ||
+	    is_ccs_plane(fb, color_plane))
 		return 4096;
 
 	switch (fb->modifier) {
@@ -2158,6 +2176,10 @@ static unsigned int intel_surf_alignment(const struct drm_framebuffer *fb,
 	case I915_FORMAT_MOD_Y_TILED_CCS:
 	case I915_FORMAT_MOD_Yf_TILED_CCS:
 	case I915_FORMAT_MOD_Y_TILED:
+		if (INTEL_GEN(dev_priv) >= 12 &&
+		    is_semiplanar_uv_plane(fb, color_plane))
+			return intel_tile_row_size(fb, color_plane);
+		/* Fall-through */
 	case I915_FORMAT_MOD_Yf_TILED:
 		return 1 * 1024 * 1024;
 	default:
@@ -2505,9 +2527,17 @@ static int intel_fb_offset_to_xy(int *x, int *y,
 {
 	struct drm_i915_private *dev_priv = to_i915(fb->dev);
 	unsigned int height;
+	u32 alignment;
+
+	if (INTEL_GEN(dev_priv) >= 12 &&
+	    is_semiplanar_uv_plane(fb, color_plane))
+		alignment = intel_tile_row_size(fb, color_plane);
+	else if (fb->modifier != DRM_FORMAT_MOD_LINEAR)
+		alignment = intel_tile_size(dev_priv);
+	else
+		alignment = 0;
 
-	if (fb->modifier != DRM_FORMAT_MOD_LINEAR &&
-	    fb->offsets[color_plane] % intel_tile_size(dev_priv)) {
+	if (alignment != 0 && fb->offsets[color_plane] % alignment) {
 		DRM_DEBUG_KMS("Misaligned offset 0x%08x for color plane %d\n",
 			      fb->offsets[color_plane], color_plane);
 		return -EINVAL;
-- 
2.23.1