Re: [PATCH] drm/ttm: Add a flag to allow drivers to skip clear-on-free

[Nirmoy Das]

Hi Christian,

On 6/24/2024 1:39 PM, Christian König wrote:

Am 24.06.24 um 12:07 schrieb Nirmoy Das:

Add TTM_TT_FLAG_CLEARED_ON_FREE, which DRM drivers can set before
releasing backing stores if they want to skip clear-on-free.

Cc: Matthew Auld <matthew.a...@intel.com>
Cc: Thomas Hellström <thomas.hellst...@linux.intel.com>
Suggested-by: Christian König <christian.koe...@amd.com>
Signed-off-by: Nirmoy Das <nirmoy....@intel.com>

Reviewed-by: Christian König <christian.koe...@amd.com>

Thanks a lot. Could you also please help get this merge ?


Regards,

Nirmoy

---
  drivers/gpu/drm/ttm/ttm_pool.c | 18 +++++++++++-------
  include/drm/ttm/ttm_tt.h       |  6 +++++-
  2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c

index 6e1fd6985ffc..b78ee7524bcf 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c

@@ -222,15 +222,18 @@ static void ttm_pool_unmap(struct ttm_pool *pool, dma_addr_t dma_addr,

  }
    /* Give pages into a specific pool_type */

-static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page *p) +static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page *p,

+                   bool cleared)
  {
      unsigned int i, num_pages = 1 << pt->order;
  -    for (i = 0; i < num_pages; ++i) {
-        if (PageHighMem(p))
-            clear_highpage(p + i);
-        else
-            clear_page(page_address(p + i));
+    if (!cleared) {
+        for (i = 0; i < num_pages; ++i) {
+            if (PageHighMem(p))
+                clear_highpage(p + i);
+            else
+                clear_page(page_address(p + i));
+        }
      }
        spin_lock(&pt->lock);

@@ -394,6 +397,7 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,

                  pgoff_t start_page, pgoff_t end_page)
  {
      struct page **pages = &tt->pages[start_page];
+    bool cleared = tt->page_flags & TTM_TT_FLAG_CLEARED_ON_FREE;
      unsigned int order;
      pgoff_t i, nr;

  @@ -407,7 +411,7 @@ static void ttm_pool_free_range(struct ttm_pool *pool, struct ttm_tt *tt,

            pt = ttm_pool_select_type(pool, caching, order);
          if (pt)
-            ttm_pool_type_give(pt, *pages);
+            ttm_pool_type_give(pt, *pages, cleared);
          else
              ttm_pool_free_page(pool, caching, order, *pages);
      }
diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
index 2b9d856ff388..cfaf49de2419 100644
--- a/include/drm/ttm/ttm_tt.h
+++ b/include/drm/ttm/ttm_tt.h
@@ -85,6 +85,9 @@ struct ttm_tt {

       * fault handling abuses the DMA api a bit and dma_map_attrs can't be

       * used to assure pgprot always matches.
       *
+     * TTM_TT_FLAG_CLEARED_ON_FREE: Set this if a drm driver handles
+     * clearing backing store
+     *

       * TTM_TT_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE. This is        * set by TTM after ttm_tt_populate() has successfully returned, and is

       * then unset when TTM calls ttm_tt_unpopulate().
@@ -94,8 +97,9 @@ struct ttm_tt {
  #define TTM_TT_FLAG_EXTERNAL        BIT(2)
  #define TTM_TT_FLAG_EXTERNAL_MAPPABLE    BIT(3)
  #define TTM_TT_FLAG_DECRYPTED        BIT(4)
+#define TTM_TT_FLAG_CLEARED_ON_FREE    BIT(5)
  -#define TTM_TT_FLAG_PRIV_POPULATED    BIT(5)
+#define TTM_TT_FLAG_PRIV_POPULATED    BIT(6)
      uint32_t page_flags;
      /** @num_pages: Number of pages in the page array. */
      uint32_t num_pages;