[PATCH 7/8] drm/i915: Bump fb stride limit to 128KiB for gen4+ and 256KiB for gen7+

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

With gtt remapping plugged in we can simply raise the stride
limit on gen4+. Let's just pick the limit to match the render
engine max stride (256KiB on gen7+, 128KiB on gen4+).

No remapping CCS because the virtual address of each page actually
matters due to the new hash mode
(WaCompressedResourceDisplayNewHashMode:skl,kbl etc.), and no
remapping on gen2/3 due extra complications from fence alignment
and gen2 2KiB GTT tile size. Also no real benefit since the
display engine limits already match the other limits.

v2: Rebase due to is_ccs_modifier()
v3: Tweak the comment and commit msg
v4: Fix gen4+ stride limit to be 128KiB

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> #v3
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index fa317c40d548..a2e4ef938d53 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2519,6 +2519,19 @@ static
 u32 intel_fb_max_stride(struct drm_i915_private *dev_priv,
 			u32 pixel_format, u64 modifier)
 {
+	/*
+	 * Arbitrary limit for gen4+ chosen to match the
+	 * render engine max stride.
+	 *
+	 * The new CCS hash mode makes remapping impossible
+	 */
+	if (!is_ccs_modifier(modifier)) {
+		if (INTEL_GEN(dev_priv) >= 7)
+			return 256*1024;
+		else if (INTEL_GEN(dev_priv) >= 4)
+			return 128*1024;
+	}
+
 	return intel_plane_fb_max_stride(dev_priv, pixel_format, modifier);
 }
 
-- 
2.21.0