Re: [PATCH 2/2] Revert "drm/ttm: Add a flag to allow drivers to skip clear-on-free"

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Wed, 2024-08-21 at 11:50 +0200, Nirmoy Das wrote:
> Remove TTM_TT_FLAG_CLEARED_ON_FREE now that XE stopped using this
> flag.
> 
> This reverts commit decbfaf06db05fa1f9b33149ebb3c145b44e878f.
> 
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

> ---
>  drivers/gpu/drm/ttm/ttm_pool.c | 18 +++++++-----------
>  include/drm/ttm/ttm_tt.h       |  6 +-----
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c
> b/drivers/gpu/drm/ttm/ttm_pool.c
> index 935ab3cfd046..8504dbe19c1a 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -222,18 +222,15 @@ 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,
> -			       bool cleared)
> +static void ttm_pool_type_give(struct ttm_pool_type *pt, struct page
> *p)
>  {
>  	unsigned int i, num_pages = 1 << pt->order;
>  
> -	if (!cleared) {
> -		for (i = 0; i < num_pages; ++i) {
> -			if (PageHighMem(p))
> -				clear_highpage(p + i);
> -			else
> -				clear_page(page_address(p + i));
> -		}
> +	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);
> @@ -397,7 +394,6 @@ 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;
>  
> @@ -411,7 +407,7 @@ 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, cleared);
> +			ttm_pool_type_give(pt, *pages);
>  		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 cfaf49de2419..2b9d856ff388 100644
> --- a/include/drm/ttm/ttm_tt.h
> +++ b/include/drm/ttm/ttm_tt.h
> @@ -85,9 +85,6 @@ 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().
> @@ -97,9 +94,8 @@ 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(6)
> +#define TTM_TT_FLAG_PRIV_POPULATED	BIT(5)
>  	uint32_t page_flags;
>  	/** @num_pages: Number of pages in the page array. */
>  	uint32_t num_pages;