TTM records the allocation order of a multi-order page in page->private at allocation time. For pools that do not use dma_alloc the order is stored directly, while dma_alloc pools store a struct ttm_pool_dma pointer there instead. Drivers that do their own DMA mapping (e.g. Xe) need the per-page order to walk a populated ttm_tt one chunk at a time, but cannot rely on folio_order(): TTM allocates high-order pages with alloc_pages_node() without __GFP_COMP, so they are not compound and folio_order() always returns 0.
Expose ttm_pool_page_order_nodma(), a thin wrapper that returns the order recorded in page->private. It is only valid for pages from a pool that does not use dma_alloc; whether a TTM device uses dma_alloc is fixed at ttm device init time, so callers know from their device configuration that this helper applies. Use it from the existing internal ttm_pool_page_order() to keep a single source of truth. Cc: Carlos Santa <[email protected]> Cc: Ryan Neph <[email protected]> Cc: Christian Koenig <[email protected]> Cc: Huang Rui <[email protected]> Cc: Matthew Auld <[email protected]> Cc: Maarten Lankhorst <[email protected]> Cc: Maxime Ripard <[email protected]> Cc: Thomas Zimmermann <[email protected]> Cc: David Airlie <[email protected]> Cc: Simona Vetter <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Thomas Hellström <[email protected]> Assisted-by: GitHub_Copilot:claude-opus-4.8 Signed-off-by: Matthew Brost <[email protected]> --- drivers/gpu/drm/ttm/ttm_pool.c | 25 ++++++++++++++++++++++++- include/drm/ttm/ttm_pool.h | 2 ++ 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c index dbe977412a81..d34592d4dbc7 100644 --- a/drivers/gpu/drm/ttm/ttm_pool.c +++ b/drivers/gpu/drm/ttm/ttm_pool.c @@ -461,6 +461,29 @@ static unsigned int ttm_pool_shrink(int nid, unsigned long num_to_free) return num_pages; } +/** + * ttm_pool_page_order_nodma() - Allocation order of a non-dma_alloc TTM page + * @p: The page to query. + * + * Return the allocation order that the TTM pool allocator recorded in + * @p->private at allocation time. This only works for pages that were + * allocated from a pool which does *not* use dma_alloc (i.e. pages backed by + * alloc_pages_node()), where TTM stores the order directly in page->private. + * + * For dma_alloc pools, page->private instead holds a struct ttm_pool_dma + * pointer and this helper must not be used. Whether a TTM device uses + * dma_alloc is fixed at ttm device init time, so callers are expected to know + * from their TTM device configuration that their pages are not dma_alloc + * backed before using this helper. + * + * Return: The allocation order of the page. + */ +unsigned int ttm_pool_page_order_nodma(struct page *p) +{ + return p->private; +} +EXPORT_SYMBOL(ttm_pool_page_order_nodma); + /* Return the allocation order based for a page */ static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p) { @@ -470,7 +493,7 @@ static unsigned int ttm_pool_page_order(struct ttm_pool *pool, struct page *p) return dma->vaddr & ~PAGE_MASK; } - return p->private; + return ttm_pool_page_order_nodma(p); } /* diff --git a/include/drm/ttm/ttm_pool.h b/include/drm/ttm/ttm_pool.h index 26ee592e1994..753203980e2c 100644 --- a/include/drm/ttm/ttm_pool.h +++ b/include/drm/ttm/ttm_pool.h @@ -94,6 +94,8 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *ttm, int ttm_pool_restore_and_alloc(struct ttm_pool *pool, struct ttm_tt *tt, const struct ttm_operation_ctx *ctx); +unsigned int ttm_pool_page_order_nodma(struct page *p); + int ttm_pool_mgr_init(unsigned long num_pages); void ttm_pool_mgr_fini(void); -- 2.34.1
