From: Jocelyn Falempe <jfalempe@redhat.com>
Date: Tue, 24 Jun 2025 09:01:14 +0000 (+0200)
Subject: drm/ttm: Add ttm_bo_kmap_try_from_panic()
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=718370ff283284f191155a5eb9d4f376aaf93bb8;p=thirdparty%2Fkernel%2Flinux.git

drm/ttm: Add ttm_bo_kmap_try_from_panic()

If the ttm bo is backed by pages, then it's possible to safely kmap
one page at a time, using kmap_try_from_panic().
Unfortunately there is no way to do the same with ioremap, so it
only supports the kmap case.
This is needed for proper drm_panic support with xe driver.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20250624091501.257661-6-jfalempe@redhat.com
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
---

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index b9a772b26fa18..ad95e8b9852b6 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -381,6 +381,33 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 	return (!map->virtual) ? -ENOMEM : 0;
 }
 
+/**
+ *
+ * ttm_bo_kmap_try_from_panic
+ *
+ * @bo: The buffer object
+ * @page: The page to map
+ *
+ * Sets up a kernel virtual mapping using kmap_local_page_try_from_panic().
+ * This should only be called from the panic handler, if you make sure the bo
+ * is the one being displayed, so is properly allocated, and protected.
+ *
+ * Returns the vaddr, that you can use to write to the bo, and that you should
+ * pass to kunmap_local() when you're done with this page, or NULL if the bo
+ * is in iomem.
+ */
+void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page)
+{
+	if (page + 1 > PFN_UP(bo->resource->size))
+		return NULL;
+
+	if (!bo->resource->bus.is_iomem && bo->ttm->pages && bo->ttm->pages[page])
+		return kmap_local_page_try_from_panic(bo->ttm->pages[page]);
+
+	return NULL;
+}
+EXPORT_SYMBOL(ttm_bo_kmap_try_from_panic);
+
 /**
  * ttm_bo_kmap
  *
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index 8ad6e27136256..5332ee74d95b1 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -401,6 +401,7 @@ int ttm_bo_init_validate(struct ttm_device *bdev, struct ttm_buffer_object *bo,
 int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page,
 		unsigned long num_pages, struct ttm_bo_kmap_obj *map);
 void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
+void *ttm_bo_kmap_try_from_panic(struct ttm_buffer_object *bo, unsigned long page);
 int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map);
 void ttm_bo_vunmap(struct ttm_buffer_object *bo, struct iosys_map *map);
 int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo);