[Intel-gfx] [PATCH v2 02/15] drm/i915/dsb: DSB context creation.

[Tvrtko Ursulin]

On 17/10/2019 13:52, Animesh Manna wrote:
> On 10/17/2019 2:05 PM, Tvrtko Ursulin wrote:
>> On 22/08/2019 13:09, Chris Wilson wrote:
>>> Quoting Animesh Manna (2019-08-22 13:05:06)
>>>> Hi,
>>>>
>>>>
>>>> On 8/21/2019 11:41 PM, Chris Wilson wrote:
>>>>> Quoting Animesh Manna (2019-08-21 07:32:22)
>>>>>> +       vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, 
>>>>>> PIN_MAPPABLE);
>>>>> Only this (currently) still requires struct_mutex
>>>>
>>>> Sure will add.
>>>>>
>>>>> Does it have to mappable? Is that the HW constraint?
>>>>
>>>> Yes, as per HW design need a cpu mapped buffer to write opcode+data 
>>>> from
>>>> driver.
>>>
>>> PIN_MAPPABLE refers to the iomem aperture portion of the Global GTT 
>>> (i.e.
>>> the low 64-512MiB). You never use a GGTT mmap for your CPU access, so 
>>> the
>>> placement should be entirely dictated by the DSB requirements. If you
>>> don't need to be in the low region, don't force it to be, so we have
>>> less congestion for the objects that have to be placed in that region.
>>
>> I was doing a mini audit of what uses the aperture these days and 
>> noticed this code has been merged in the meantime, but AFAICS this 
>> question from Chris hasn't been answered? At least not on the mailing 
>> list. So does it need to be in the aperture region or not?
> 
> Hi,
> 
> Based on recommendation from H/w team used PIN_MAPPABLE, not very sure 
> about internal details.

What did the recommendation exactly say? That it has to be in GGTT or 
aperture?

Regards,

Tvrtko