Re: [PATCH 4/5] drm/xe/xe2: Limit ccs framebuffers to tile4 only

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Hey,

On 2024-01-30 20:16, Juha-Pekka Heikkila wrote:
> On 29.1.2024 14.02, Matthew Auld wrote:
>> On 26/01/2024 21:08, Juha-Pekka Heikkila wrote:
>>> Display engine support ccs only with tile4, prevent other modifiers
>>> from using compressed memory. Store pin time pat index to xe_bo.
>>>
>>> Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
>>> ---
>>>   drivers/gpu/drm/xe/display/xe_fb_pin.c | 19 +++++++++++++++++++
>>>   1 file changed, 19 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/xe/display/xe_fb_pin.c 
>>> b/drivers/gpu/drm/xe/display/xe_fb_pin.c
>>> index 722c84a56607..b2930a226f54 100644
>>> --- a/drivers/gpu/drm/xe/display/xe_fb_pin.c
>>> +++ b/drivers/gpu/drm/xe/display/xe_fb_pin.c
>>> @@ -10,9 +10,18 @@
>>>   #include "intel_fb_pin.h"
>>>   #include "xe_ggtt.h"
>>>   #include "xe_gt.h"
>>> +#include "xe_pat.h"
>>>   #include <drm/ttm/ttm_bo.h>
>>> +static bool is_compressed(const struct drm_framebuffer *fb)
>>> +{
>>> +    struct xe_bo *bo = intel_fb_obj(fb);
>>> +    struct xe_device *xe = 
>>> to_xe_device(to_intel_framebuffer(fb)->base.dev);
>>> +
>>> +    return xe_pat_index_has_compression(xe, bo->pat_index);
>>> +}
>>> +
>>>   static void
>>>   write_dpt_rotated(struct xe_bo *bo, struct iosys_map *map, u32 
>>> *dpt_ofs, u32 bo_ofs,
>>>             u32 width, u32 height, u32 src_stride, u32 dst_stride)
>>> @@ -349,12 +358,22 @@ void intel_unpin_fb_vma(struct i915_vma *vma, 
>>> unsigned long flags)
>>>   int intel_plane_pin_fb(struct intel_plane_state *plane_state)
>>>   {
>>>       struct drm_framebuffer *fb = plane_state->hw.fb;
>>> +    struct xe_device *xe = 
>>> to_xe_device(to_intel_framebuffer(fb)->base.dev);
>>>       struct xe_bo *bo = intel_fb_obj(fb);
>>>       struct i915_vma *vma;
>>>       /* We reject creating !SCANOUT fb's, so this is weird.. */
>>>       drm_WARN_ON(bo->ttm.base.dev, !(bo->flags & XE_BO_SCANOUT_BIT));
>>> +    if (GRAPHICS_VER(xe) >= 20) {
>>> +        if (fb->modifier != I915_FORMAT_MOD_4_TILED &&
>>> +            is_compressed(fb)) {
>>> +            drm_warn(&xe->drm, "Cannot create ccs framebuffer with 
>>> other than tile4 mofifier\n");
>>> +            return -EINVAL;
>>> +        }
>>> +        bo->pat_index_scanout = bo->pat_index;
>>> +    }
>>
>> I think this needs to be moved into __xe_pin_fb_vma() after acquiring 
>> the object lock. Also not sure what prevents vm_bind appearing after 
>> we drop the lock? Do we need to prevent modifications until the end of 
>> _xe_unpin_fb_vma()?
> 
> I did now put in __xe_unpin_fb_vma()
> ..
> vma->bo->has_sealed_pat_index = false;
> ..
> 
> as well as moved this above block to correct place.
I'm pretty sure this will fail if the BO is pinned more than once 
simultaneously. Should probably be a refcount protected by bo lock instead.

Is the harm from allowing this only having a garbled display?

If so, we might as well allow it, and avoid complicating the bind code 
even more.

Cheers,
~Maarten