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From: Lukas Wunner <lukas@wunner.de>
To: Lyude Paul <lyude@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	nouveau@lists.freedesktop.org,
	Karol Herbst <karolherbst@gmail.com>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH v3 3/8] drm/fb_helper: Introduce hotplug_suspend/resume()
Date: Mon, 6 Aug 2018 21:34:57 +0200	[thread overview]
Message-ID: <20180806193457.GA7028@wunner.de> (raw)
In-Reply-To: <4e72a10062166d646ebd3eb28b6c186d4c00a63f.camel@redhat.com>

On Mon, Aug 06, 2018 at 03:15:31PM -0400, Lyude Paul wrote:
> You did mention in the review of one of my other patches that we should avoid
> disabling polling during runtime suspend, and you're definitely right. I feel
> a bit silly for not remembering that since I was the one who made it so that
> i915 does polling in runtime suspend for chips without RPM HPD detection in
> the first place because it was causing people's displays not to come up on
> vlv...
> Anyway: I think if we just leave output polling enabled during runtime suspend
> that might actually fix all of the fb_helper locking issues since we won't
> need to wait on any of the output poll workers to finish, at least I think it
> should: I'll confirm this when I get into the office

Quoth Imre Deak:

   "In i915 polling is on during runtime suspend only if there are outputs
    without hotplug interrupt support. A special case is when an output has
    working HPD interrupts when in D0, but no interrupts when runtime
    suspended. For these we start polling (from a scheduled work) in the
    runtime suspend hook and stop it in the runtime resume hook (again from
    a scheduled work)."
    https://lkml.org/lkml/2018/2/12/330

nouveau only uses runtime PM on discrete GPUs in dual GPU laptops.
Resuming the GPU from D3cold to D0 every few seconds to poll the
outputs would waste too much power on such machines.

The question is, why is polling running at all, since all modern
laptops have HPD-capable ports such as DP?

Thanks,

Lukas

WARNING: multiple messages have this Message-ID (diff)
From: Lukas Wunner <lukas-JFq808J9C/izQB+pC5nmwQ@public.gmane.org>
To: Lyude Paul <lyude-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: David Airlie <airlied-cv59FeDIM0c@public.gmane.org>,
	nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Daniel Vetter <daniel-/w4YWyX8dFk@public.gmane.org>
Subject: Re: [PATCH v3 3/8] drm/fb_helper: Introduce hotplug_suspend/resume()
Date: Mon, 6 Aug 2018 21:34:57 +0200	[thread overview]
Message-ID: <20180806193457.GA7028@wunner.de> (raw)
In-Reply-To: <4e72a10062166d646ebd3eb28b6c186d4c00a63f.camel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On Mon, Aug 06, 2018 at 03:15:31PM -0400, Lyude Paul wrote:
> You did mention in the review of one of my other patches that we should avoid
> disabling polling during runtime suspend, and you're definitely right. I feel
> a bit silly for not remembering that since I was the one who made it so that
> i915 does polling in runtime suspend for chips without RPM HPD detection in
> the first place because it was causing people's displays not to come up on
> vlv...
> Anyway: I think if we just leave output polling enabled during runtime suspend
> that might actually fix all of the fb_helper locking issues since we won't
> need to wait on any of the output poll workers to finish, at least I think it
> should: I'll confirm this when I get into the office

Quoth Imre Deak:

   "In i915 polling is on during runtime suspend only if there are outputs
    without hotplug interrupt support. A special case is when an output has
    working HPD interrupts when in D0, but no interrupts when runtime
    suspended. For these we start polling (from a scheduled work) in the
    runtime suspend hook and stop it in the runtime resume hook (again from
    a scheduled work)."
    https://lkml.org/lkml/2018/2/12/330

nouveau only uses runtime PM on discrete GPUs in dual GPU laptops.
Resuming the GPU from D3cold to D0 every few seconds to poll the
outputs would waste too much power on such machines.

The question is, why is polling running at all, since all modern
laptops have HPD-capable ports such as DP?

Thanks,

Lukas
_______________________________________________
Nouveau mailing list
Nouveau@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/nouveau

  reply	other threads:[~2018-08-06 19:35 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-31  0:39 [PATCH v3 0/8] Fix connector probing deadlocks from RPM bugs Lyude Paul
2018-07-31  0:39 ` Lyude Paul
2018-07-31  0:39 ` [PATCH v3 1/8] drm/nouveau: Fix bogus drm_kms_helper_poll_enable() placement Lyude Paul
2018-07-31  0:39 ` [PATCH v3 2/8] drm/nouveau: Enable polling even if we have runtime PM Lyude Paul
2018-07-31  0:39   ` Lyude Paul
2018-07-31  0:39 ` [PATCH v3 3/8] drm/fb_helper: Introduce hotplug_suspend/resume() Lyude Paul
2018-07-31  0:39   ` Lyude Paul
     [not found]   ` <20180731003954.19962-4-lyude-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2018-07-31 14:14     ` William Lewis
2018-08-01  8:36   ` kbuild test robot
2018-08-01  9:53   ` kbuild test robot
2018-08-01  9:53     ` kbuild test robot
2018-08-06  8:43   ` Daniel Vetter
2018-08-06 19:15     ` Lyude Paul
2018-08-06 19:34       ` Lukas Wunner [this message]
2018-08-06 19:34         ` Lukas Wunner
2018-08-06 19:43         ` Daniel Vetter
2018-08-06 19:43           ` Daniel Vetter
2018-08-06 19:45         ` Alex Deucher
2018-08-06 19:45           ` Alex Deucher
2018-07-31  0:39 ` [PATCH v3 4/8] drm/nouveau: Fix deadlock with fb_helper using new helpers Lyude Paul
2018-07-31  0:39   ` Lyude Paul
2018-07-31  0:39 ` [PATCH v3 5/8] drm/nouveau: Use pm_runtime_get_noresume() in connector_detect() Lyude Paul
2018-07-31  0:39   ` Lyude Paul
2018-07-31  0:39 ` [PATCH v3 6/8] drm/nouveau: Respond to HPDs by probing one conn at a time Lyude Paul
2018-07-31  0:39 ` [PATCH v3 7/8] drm/nouveau: Fix deadlocks in nouveau_connector_detect() Lyude Paul
2018-07-31  0:39 ` [PATCH v3 8/8] drm/nouveau: Call pm_runtime_get_noresume() from hpd handlers Lyude Paul

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