drm/xe: Use ttm_uncached for BO with NEEDS_UC flag

We should honor requested uncached mode also at the TTM layer.
Otherwise, we risk losing updates to the memory based interrupts
source or status vectors, as those require uncached memory.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240618104947.729-1-michal.wajdeczko@intel.com

diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index 74294f1b05bc3222e83f02e7d51733ece4673393..65c696966e96c476cb2e25c5132a11fabad2f2c9 100644 (file)
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -378,6 +378,15 @@ static struct ttm_tt *xe_ttm_tt_create(struct ttm_buffer_object *ttm_bo,
            (xe->info.graphics_verx100 >= 1270 && bo->flags & XE_BO_FLAG_PAGETABLE))
                caching = ttm_write_combined;
 
+       if (bo->flags & XE_BO_FLAG_NEEDS_UC) {
+               /*
+                * Valid only for internally-created buffers only, for
+                * which cpu_caching is never initialized.
+                */
+               xe_assert(xe, bo->cpu_caching == 0);
+               caching = ttm_uncached;
+       }
+
        err = ttm_tt_init(&tt->ttm, &bo->ttm, page_flags, caching, extra_pages);
        if (err) {
                kfree(tt);