On 16/09/2022 11:30, Gupta, Anshuman wrote:
-----Original Message-----
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
Sent: Thursday, September 15, 2022 10:37 PM
To: Gupta, Anshuman <anshuman.gupta@xxxxxxxxx>; intel-
gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Auld, Matthew <matthew.auld@xxxxxxxxx>; Vivi, Rodrigo
<rodrigo.vivi@xxxxxxxxx>
Subject: Re: [RFC 1/1] drm/i915/dgfx: Handling of pin_map against
rpm
On 15/09/2022 11:33, Anshuman Gupta wrote:
If i915 gem obj lies in lmem, then i915_gem_object_pin_map need to
grab a rpm wakeref to make sure gfx PCIe endpoint function stays in D0
state during any access to mapping returned by
i915_gem_object_pin_map().
Subsequently i915_gem_object_upin_map will put the wakref as well.
Another thing to check are perma pinned contexts. Follow the flow from
intel_engine_create_pinned_context to intel_engine_destroy_pinned_context.
If you find out that kernel (&co) contexts are pinned for the duration of i915
load/bind and that they use lmem objects, that would mean wakeref is held for
the duration of i915 loaded state. Defeating the point and making the solution
effectively equal to just disabling RPM.
That’s correct intel_ring_pin can pin_map the lmem object.
if (i915_vma_is_map_and_fenceable(vma)) {
addr = (void __force *)i915_vma_pin_iomap(vma);
} else {
int type = i915_coherent_map_type(vma->vm->i915, vma->obj, false);
addr = i915_gem_object_pin_map(vma->obj, type);
}
If that is the case this RFC proposal will not work and in that case
Right, or LRC state for perma pinned contexts is probably even more
clear cut.
every caller of i915_gem_object_pin_map need to grab the wakreref before
accessing the retuned address by pin_map. Any inputs from you side for any other approach.
I didn't quite get what you meant here.
My point was that if my thinking that perma pinned contexts would hold
the wakeref permanently is correct, that would prevent the approach from
this patch to have a different effect from just disabling RPM. Would
unpinning the perma pinned contexts on GT park be feasible? It's not a 5
minute question and unfortunately I don't have enough time to go deep
into this problem space. Like Hopefully someone else can jump in.
Regards,
Tvrtko
