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

[Nirmoy Das]

Hi Christian,

On 6/24/2024 2:21 PM, Christian König wrote:
> Am 24.06.24 um 14:19 schrieb 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.auld at intel.com>
>>>> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
>>>> Suggested-by: Christian König <christian.koenig at amd.com>
>>>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>>>
>>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>
>> Thanks a lot. Could you also please help get this merge ?
>
> I can push it to drm-misc-next, but for that I also need a patch 
> actually using it.

Ah okay.


>
> On the other hand feel free to merge that through the i915 or xe 
> branch as well. The patch is small enough so that it probably won't 
> cause any merge conflict.

I need to polish the XE patch a bit. I will get that merge through xe 
branch then.


Thanks,

Nirmoy

>
> Regards,
> Christian.
>
>>
>>
>> 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;
>>>
>