[SRU][resolute][PATCH 1/1] UBUNTU: SAUCE: drm/xe/display: skip FORCE_WC and vm_bound check for external dma-bufs

[ChunAn Wu]

From: Matthew Auld <matthew.auld at intel.com>

BugLink: https://bugs.launchpad.net/bugs/2158605

Currently, xe_display_bo_framebuffer_init() unconditionally attempts to
apply XE_BO_FLAG_FORCE_WC to the buffer and rejects the FB creation with
-EINVAL if the BO is already VM_BINDed.

However, for imported dma-bufs (ttm_bo_type_sg), this check doesn't seem
to make much sense since CPU caching policy is entirely controlled by
the exporter. Plus there is no place to set this flag, in the first
place. Also this is not rejected if not yet vm_binded, but that seems
arbitrary since setting or not setting FORCE_WC should a noop either
way, at this stage, and whether it is currently VM_BINDed makes no
difference.

Currently if we run an app and offload rendering to an external dGPU,
like NV or another xe device, the dma-buf passed back to the compositor
(igpu) will be an actual external import from xe pov, and it will be
missing FORCE_WC, and if the compositor side did a VM_BIND before
turning into it into an fb the whole thing gets rejected.

So it looks like we either need to reject outright, no matter what, or
this usecase is valid and we need to loosen the restriction for sg
buffers. Proposing here to loosen the restriction.

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/7919
Link: https://patchwork.freedesktop.org/patch/732636/
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Maarten Lankhorst <dev at lankhorst.se>
Reviewed-by: Maarten Lankhorst <dev at lankhorst.se>
[anwu: Backported from Patchwork. Ubuntu trees still carry this code in
 intel_fb_bo.c rather than xe_display_bo.c, and use SCANOUT flag names,
 so apply the same ttm_bo_type_sg exemption to the local framebuffer
 init and pin checks.]
Co-authored-by: Copilot <223556219+Copilot at users.noreply.github.com>
Signed-off-by: ChunAn Wu <an.wu at canonical.com>
---
 drivers/gpu/drm/xe/display/intel_fb_bo.c | 3 ++-
 drivers/gpu/drm/xe/display/xe_fb_pin.c   | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/xe/display/intel_fb_bo.c b/drivers/gpu/drm/xe/display/intel_fb_bo.c
index b21da7b745a5..4560825656db 100644
--- a/drivers/gpu/drm/xe/display/intel_fb_bo.c
+++ b/drivers/gpu/drm/xe/display/intel_fb_bo.c
@@ -33,7 +33,8 @@ int intel_fb_bo_framebuffer_init(struct intel_framebuffer *intel_fb,
 	if (ret)
 		return ret;
 
-	if (!(bo->flags & XE_BO_SCANOUT_BIT)) {
+	if (!(bo->flags & XE_BO_SCANOUT_BIT) &&
+	    bo->ttm.type != ttm_bo_type_sg) {
 		/*
 		 * XE_BO_SCANOUT_BIT should ideally be set at creation, or is
 		 * automatically set when creating FB. We cannot change caching
diff --git a/drivers/gpu/drm/xe/display/xe_fb_pin.c b/drivers/gpu/drm/xe/display/xe_fb_pin.c
index 722c84a56607..6ae98696a20d 100644
--- a/drivers/gpu/drm/xe/display/xe_fb_pin.c
+++ b/drivers/gpu/drm/xe/display/xe_fb_pin.c
@@ -353,7 +353,8 @@ int intel_plane_pin_fb(struct intel_plane_state *plane_state)
 	struct i915_vma *vma;
 
 	/* We reject creating !SCANOUT fb's, so this is weird.. */
-	drm_WARN_ON(bo->ttm.base.dev, !(bo->flags & XE_BO_SCANOUT_BIT));
+	drm_WARN_ON(bo->ttm.base.dev, !(bo->flags & XE_BO_SCANOUT_BIT) &&
+		    bo->ttm.type != ttm_bo_type_sg);
 
 	vma = __xe_pin_fb_vma(to_intel_framebuffer(fb), &plane_state->view.gtt);
 	if (IS_ERR(vma))
-- 
2.34.1