Re: [PATCH v3] drm/i915: Flush WC GGTT only on required platforms

[Nirmoy Das <nirmoy.das@linux.intel.com>]

This is now merged to gt-next


Thanks,

Nirmoy

On 10/18/2023 4:04 PM, Nirmoy Das wrote:
>
> On 10/18/2023 3:00 PM, Andi Shyti wrote:
>> Hi Nirmoy,
>>
>>>>> gen8_ggtt_invalidate() is only needed for limited set of platforms
>>>>> where GGTT is mapped as WC. This was added as way to fix WC based 
>>>>> GGTT in
>>>>> commit 0f9b91c754b7 ("drm/i915: flush system agent TLBs on SNB") and
>>>>> there are no reference in HW docs that forces us to use this on 
>>>>> non-WC
>>>>> backed GGTT.
>>>>>
>>>>> This can also cause unwanted side-effects on XE_HP platforms where
>>>>> GFX_FLSH_CNTL_GEN6 is not valid anymore.
>>>>>
>>>>> v2: Add a func to detect wc ggtt detection (Ville)
>>>>> v3: Improve commit log and add reference commit (Daniel)
>>>>>
>>>>> Fixes: d2eae8e98d59 ("drm/i915/dg2: Drop force_probe requirement")
>>>> I'm wondering if this is the right Fixes, though. Should this
>>>> rather be:
>>>>
>>>> Fixes: 6266992cf105 ("drm/i915/gt: remove GRAPHICS_VER == 10")
>>> Hard to find a real Fixes for this. I just want to backport this to dg2
>>> where we can have unwanted side-effects.
>> yes, this piece of code has moved around enough so to make it
>> diffuclt to track its origin.
>>
>> I think the one I found should be the correct one,
>
> That just removes a graphics ver, not related to WC GGTT map or XE_HP.
>
>>   but the dg2
>> force probe removeal can also become a placeholder for DG2 fixes.
>
> Yes, I have no better ideas too.
>
>
> Regards,
>
> Nirmoy
>
>>
>> I won't complain.
>>
>> Andi