[Intel-gfx] [PATCH 2/3] drm/i915/gt: create workqueue dedicated to wake references
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Fri May 12 12:16:33 UTC 2023
On 12/05/2023 10:54, Coelho, Luciano wrote:
> On Fri, 2023-05-12 at 10:32 +0100, Tvrtko Ursulin wrote:
>> On 12/05/2023 10:10, Coelho, Luciano wrote:
>>> On Fri, 2023-05-12 at 10:04 +0100, Tvrtko Ursulin wrote:
>>>> On 11/05/2023 09:20, Luca Coelho wrote:
>>>>> Add a work queue in the intel_wakeref structure to be used exclusively
>>>>> by the wake reference mechanism. This is needed in order to avoid
>>>>> using the system workqueue and relying on flush_scheduled_work().
>>>>>
>>>>> Cc: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
>>>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>>>> Cc: Jani Nikula <jani.nikula at intel.com>
>>>>> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>>>> Signed-off-by: Luca Coelho <luciano.coelho at intel.com>
>>>>> ---
>>>>> drivers/gpu/drm/i915/gt/intel_engine_cs.c | 7 ++++++-
>>>>> drivers/gpu/drm/i915/gt/intel_engine_pm.c | 15 ++++++++++++--
>>>>> drivers/gpu/drm/i915/gt/intel_engine_pm.h | 3 ++-
>>>>> drivers/gpu/drm/i915/gt/mock_engine.c | 8 +++++++-
>>>>> drivers/gpu/drm/i915/intel_wakeref.c | 21 ++++++++++++++-----
>>>>> drivers/gpu/drm/i915/intel_wakeref.h | 25 +++++++++++++++--------
>>>>> 6 files changed, 60 insertions(+), 19 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>>>>> index 0aff5bb13c53..6505bfa70cd0 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
>>>>> @@ -1290,7 +1290,11 @@ static int engine_setup_common(struct intel_engine_cs *engine)
>>>>> goto err_cmd_parser;
>>>>>
>>>>> intel_engine_init_execlists(engine);
>>>>> - intel_engine_init__pm(engine);
>>>>> +
>>>>> + err = intel_engine_init__pm(engine);
>>>>> + if (err)
>>>>> + goto err_cmd_parser;
>>>>> +
>>>>> intel_engine_init_retire(engine);
>>>>>
>>>>> /* Use the whole device by default */
>>>>> @@ -1525,6 +1529,7 @@ void intel_engine_cleanup_common(struct intel_engine_cs *engine)
>>>>> {
>>>>> GEM_BUG_ON(!list_empty(&engine->sched_engine->requests));
>>>>>
>>>>> + intel_engine_destroy__pm(engine);
>>>>> i915_sched_engine_put(engine->sched_engine);
>>>>> intel_breadcrumbs_put(engine->breadcrumbs);
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
>>>>> index ee531a5c142c..859b62cf660f 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
>>>>> @@ -294,14 +294,25 @@ static const struct intel_wakeref_ops wf_ops = {
>>>>> .put = __engine_park,
>>>>> };
>>>>>
>>>>> -void intel_engine_init__pm(struct intel_engine_cs *engine)
>>>>> +int intel_engine_init__pm(struct intel_engine_cs *engine)
>>>>> {
>>>>> struct intel_runtime_pm *rpm = engine->uncore->rpm;
>>>>> + int err;
>>>>> +
>>>>> + err = intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
>>>>> + if (err)
>>>>> + return err;
>>>>>
>>>>> - intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
>>>>> intel_engine_init_heartbeat(engine);
>>>>>
>>>>> intel_gsc_idle_msg_enable(engine);
>>>>> +
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> +void intel_engine_destroy__pm(struct intel_engine_cs *engine)
>>>>> +{
>>>>> + intel_wakeref_destroy(&engine->wakeref);
>>>>> }
>>>>>
>>>>> /**
>>>>> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.h b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
>>>>> index d68675925b79..e8568f7d10c6 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.h
>>>>> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.h
>>>>> @@ -104,7 +104,8 @@ intel_engine_create_kernel_request(struct intel_engine_cs *engine)
>>>>> return rq;
>>>>> }
>>>>>
>>>>> -void intel_engine_init__pm(struct intel_engine_cs *engine);
>>>>> +int intel_engine_init__pm(struct intel_engine_cs *engine);
>>>>> +void intel_engine_destroy__pm(struct intel_engine_cs *engine);
>>>>>
>>>>> void intel_engine_reset_pinned_contexts(struct intel_engine_cs *engine);
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/gt/mock_engine.c b/drivers/gpu/drm/i915/gt/mock_engine.c
>>>>> index c0637bf799a3..0a3c702c21e2 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/mock_engine.c
>>>>> +++ b/drivers/gpu/drm/i915/gt/mock_engine.c
>>>>> @@ -336,6 +336,7 @@ static void mock_engine_release(struct intel_engine_cs *engine)
>>>>> intel_context_put(engine->kernel_context);
>>>>>
>>>>> intel_engine_fini_retire(engine);
>>>>> + intel_engine_destroy__pm(engine);
>>>>> }
>>>>>
>>>>> struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
>>>>> @@ -393,6 +394,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
>>>>> int mock_engine_init(struct intel_engine_cs *engine)
>>>>> {
>>>>> struct intel_context *ce;
>>>>> + int err;
>>>>>
>>>>> INIT_LIST_HEAD(&engine->pinned_contexts_list);
>>>>>
>>>>> @@ -402,7 +404,11 @@ int mock_engine_init(struct intel_engine_cs *engine)
>>>>> engine->sched_engine->private_data = engine;
>>>>>
>>>>> intel_engine_init_execlists(engine);
>>>>> - intel_engine_init__pm(engine);
>>>>> +
>>>>> + err = intel_engine_init__pm(engine);
>>>>> + if (err)
>>>>> + return err;
>>>>> +
>>>>> intel_engine_init_retire(engine);
>>>>>
>>>>> engine->breadcrumbs = intel_breadcrumbs_create(NULL);
>>>>> diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
>>>>> index dfd87d082218..6bae609e1312 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_wakeref.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_wakeref.c
>>>>> @@ -74,7 +74,7 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags)
>>>>>
>>>>> /* Assume we are not in process context and so cannot sleep. */
>>>>> if (flags & INTEL_WAKEREF_PUT_ASYNC || !mutex_trylock(&wf->mutex)) {
>>>>> - mod_delayed_work(system_wq, &wf->work,
>>>>> + mod_delayed_work(wf->wq, &wf->work,
>>>>> FIELD_GET(INTEL_WAKEREF_PUT_DELAY, flags));
>>>>> return;
>>>>> }
>>>>> @@ -93,10 +93,10 @@ static void __intel_wakeref_put_work(struct work_struct *wrk)
>>>>> ____intel_wakeref_put_last(wf);
>>>>> }
>>>>>
>>>>> -void __intel_wakeref_init(struct intel_wakeref *wf,
>>>>> - struct intel_runtime_pm *rpm,
>>>>> - const struct intel_wakeref_ops *ops,
>>>>> - struct intel_wakeref_lockclass *key)
>>>>> +int __intel_wakeref_init(struct intel_wakeref *wf,
>>>>> + struct intel_runtime_pm *rpm,
>>>>> + const struct intel_wakeref_ops *ops,
>>>>> + struct intel_wakeref_lockclass *key)
>>>>> {
>>>>> wf->rpm = rpm;
>>>>> wf->ops = ops;
>>>>> @@ -105,9 +105,20 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
>>>>> atomic_set(&wf->count, 0);
>>>>> wf->wakeref = 0;
>>>>>
>>>>> + wf->wq = alloc_workqueue("i1915-wakeref", 0, 0);
>>>>
>>>> Typo here -
>>>
>>> Oh, good catch! This is one of my "favorite" typos, for some reason.
>>
>> Yes, I had the same one. :) Patch 3/3 too.
>>
>>>> I wanted to ask however - why does this particular wq
>>>> "deserves" to be dedicated and can't just use one of the
>>>> drm_i915_private ones?
>>>
>>> It's because there's no easy way to get access to the drm_i915_private
>>> structure from here. And I don't think this work needs to be in sync
>>> with the rest of the works in i915.
>>
>> Yeah I don't think it needs to be synchronised either. Was just thinking
>> if we really need to be creating a bunch of separate workqueues (one per
>> engine) for not much use, or instead could just add a backpointer to
>> either intel_wakeref or intel_runtime_pm. Latter already has rpm->kdev
>> so could plausably be replaced with rpm->i915.
>>
>> Actually, looking at intel_runtime_pm_init_early, you could get to i915
>> via wf->rpm and container_of.
>
> Yeah, I considered that, but using container_of() can be problematic
> when we're not sure where exactly the element is coming from. My worry
> was this:
>
> int intel_engine_init__pm(struct intel_engine_cs *engine)
> {
> struct intel_runtime_pm *rpm = engine->uncore->rpm;
> int err;
>
> err = intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
> [...]
> }
>
> In this case, we're getting to __intel_wakeref_init() with an *rpm that
> is coming from an intel_uncore structure and not from
> drm_i915_private...
Right. Yes I agree that would be a flaky/questionable design, even if it
worked in practice. I'd just replace rpm->dev with rpm->i915 then. Not
feeling *that* strongly about it, but it just feels a waste to create a
bunch of workqueues for this.
Regards,
Tvrtko
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