drm/panfrost: Check sgt to know whether pages are already mapped

In the MMU's page fault ISR for a heap object, determine whether the
faulting address belongs to a 2MiB block that was already mapped by
checking its corresponding sgt in the Panfrost BO.

This is done in preparation for a future commit in which the MMU mapping
helper might fail, but the page array is left populated, so this cannot
be used as a check for an early bail-out.

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Link: https://lore.kernel.org/r/20251019145225.3621989-6-adrian.larumbe@collabora.com
Signed-off-by: Steven Price <steven.price@arm.com>

diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index fd148d5746c0418bf2c893836e5730d54e422ae5..17897edaa2b4adb94d0b3287874c33321c2e1ea9 100644 (file)
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -602,10 +602,12 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
                refcount_set(&bo->base.pages_use_count, 1);
        } else {
                pages = bo->base.pages;
-               if (pages[page_offset]) {
-                       /* Pages are already mapped, bail out. */
-                       goto out;
-               }
+       }
+
+       sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)];
+       if (sgt->sgl) {
+               /* Pages are already mapped, bail out. */
+               goto out;
        }
 
        mapping = bo->base.base.filp->f_mapping;
@@ -627,7 +629,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
                }
        }
 
-       sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)];
        ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
                                        NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL);
        if (ret)