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

[Nirmoy Das <nirmoy.das@xxxxxxxxx>]

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.auld@xxxxxxxxx>
> > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > Suggested-by: Christian König <christian.koenig@xxxxxxx>
> > Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx>

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;