Re: [Intel-gfx] [PATCH v5 4/5] drm/i915/display: consider DG2_RC_CCS_CC when migrating buffers

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 11/10/2022 16:28, Matthew Auld wrote:
> On 11/10/2022 16:03, Tvrtko Ursulin wrote:
>>
>> On 11/10/2022 15:39, Matthew Auld wrote:
>>> Hi,
>>>
>>> On 11/10/2022 14:54, Tvrtko Ursulin wrote:
>>>>
>>>> Hi Matt,
>>>>
>>>> On 04/10/2022 14:19, Matthew Auld wrote:
>>>>> For these types of display buffers, we need to able to CPU access some
>>>>> part of the backing memory in prepare_plane_clear_colors(). As a 
>>>>> result
>>>>> we need to ensure we always place in the mappable part of lmem, which
>>>>> becomes necessary on small-bar systems.
>>>>>
>>>>> v2(Nirmoy & Ville):
>>>>>   - Add some commentary for why we need to CPU access the buffer.
>>>>>   - Split out the other changes, so we just consider the display 
>>>>> change
>>>>>     here.
>>>>> v3:
>>>>>   - Handle this in the dpt path.
>>>>> v4(Ville):
>>>>>   - Drop the intel_fb_rc_ccs_cc_plane() sanity check in
>>>>>     pin_and_fence_fb_obj(), since we can also trigger this on DG1 it
>>>>>     seems.
>>>>>
>>>>> Fixes: eb1c535f0d69 ("drm/i915: turn on small BAR support")
>>>>
>>>> That one landed in 6.0 - do you want to send this (with 
>>>> pre-requisite(s)) to stable? Or if not do you want me to send for 
>>>> 6.1 as part of fixes flow? In which case what are the per-requisites?
>>>
>>> This one is only for DG2, which is still hidden behind force_probe, 
>>> so not too sure if it needs stable? I think the only pre-requisite is 
>>> 999f45620772 ("drm/i915: allow control over the flags when 
>>> migrating"), but again I'm not too sure how much we care about fixes 
>>> for platforms hidden behind force_probe? What do you think?
>>
>> It is certainly not mandatory, but now that cards are about to ship 
>> and reach end users it may be nice to have if not too hard - at least 
>> for 6.1 release candidates. I am not clear on the importance of the 
>> fix to say for sure. Like what goes bang and under what circumstances. 
>> So I do basically defer to someone who knows those answers.
> 
> It's important for small-bar DG2 systems, where it will potentially oops 
> somewhere in the driver without this, so if we want to support DG2 as a 
> platform in 6.1, then we also need this fix, along with 999f45620772.

Now that you mention an oops I will definitely aim to pull it in. Thanks!

Regards,

Tvrtko