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 <jfale...@redhat.com>
---
v8:
* Added in v8
v9:
* Fix comment in ttm_bo_kmap_try_from_panic(), this can *only* be called
from the panic handler (Christian König)
drivers/gpu/drm/ttm/ttm_bo_util.c | 27 +++++++++++++++++++++++++++
include/drm/ttm/ttm_bo.h | 1 +
2 files changed, 28 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c
b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 15cab9bda17f..6912e6dfda25 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -377,6 +377,33 @@ 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 cf027558b6db..8c0ce3fa077f 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -429,6 +429,7 @@ 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);
--
2.49.0
