[Intel-gfx] [PATCH V2] drm/i915: Use I915_MAP_WC for execlists context buffer on the platforms without LLC

[Zhao, Yakui]

>-----Original Message-----
>From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
>Sent: Friday, June 22, 2018 3:37 PM
>To: Zhao, Yakui <yakui.zhao at intel.com>; intel-gfx at lists.freedesktop.org
>Subject: RE: [PATCH V2] drm/i915: Use I915_MAP_WC for execlists context
>buffer on the platforms without LLC
>
>Quoting Zhao, Yakui (2018-06-22 08:29:15)
>>
>>
>> >-----Original Message-----
>> >From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
>> >Sent: Friday, June 22, 2018 2:36 PM
>> >To: Zhao, Yakui <yakui.zhao at intel.com>;
>> >intel-gfx at lists.freedesktop.org
>> >Cc: Zhao, Yakui <yakui.zhao at intel.com>
>> >Subject: Re: [PATCH V2] drm/i915: Use I915_MAP_WC for execlists
>> >context buffer on the platforms without LLC
>> >
>> >Quoting Zhao Yakui (2018-06-22 07:09:10)
>> >> @@ -2728,6 +2729,7 @@ populate_lr_context(struct i915_gem_context
>*ctx,
>> >>                     struct intel_engine_cs *engine,
>> >>                     struct intel_ring *ring)  {
>> >> +       enum i915_map_type map = HAS_LLC(ctx->i915) ? I915_MAP_WB :
>> >> + I915_MAP_WC;
>> >>         void *vaddr;
>> >>         u32 *regs;
>> >>         int ret;
>> >> @@ -2738,13 +2740,12 @@ populate_lr_context(struct
>i915_gem_context
>> >*ctx,
>> >>                 return ret;
>> >>         }
>> >>
>> >> -       vaddr = i915_gem_object_pin_map(ctx_obj, I915_MAP_WB);
>> >> +       vaddr = i915_gem_object_pin_map(ctx_obj, map);
>> >
>> >As this uses the cpu domain and flushed afterwards, this one is
>> >correct in its usage of MAP_WB.
>>
>> In this function the content of context state is flushed.
>>
>> But the function of execlists_submit_ports will update it again before writing
>the ELSP port.
>> And there is no flush. In fact after the ELSP port is written, the HW will start
>to execute the submitted commands.
>
>That's a different map.

Really?  It is allocated in one gem obj.

Will you please help to point out where to handle the different map?

Thanks
     Yakui

>-Chris