Re: [PATCH 3/4] drm: Only lastclose on unload for legacy drivers

From: "Michel Dänzer" <michel@daenzer.net>
To: Daniel Vetter <daniel.vetter@ffwll.ch>,
	Alex Deucher <alexdeucher@gmail.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	DRI Development <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 3/4] drm: Only lastclose on unload for legacy drivers
Date: Fri, 4 Aug 2017 13:12:36 +0900	[thread overview]
Message-ID: <da6d83e5-4e3e-0d54-37e5-4f3cacb652f2@daenzer.net> (raw)
In-Reply-To: <CAKMK7uG2XNYk-7uc0Rf27SseKcknCXeqL-RRdajCDeX5ceQ4+Q@mail.gmail.com>

On 03/08/17 10:54 PM, Daniel Vetter wrote:
> On Thu, Aug 3, 2017 at 1:17 AM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>> On Wed, Aug 2, 2017 at 10:50 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
>>> On Wed, Aug 2, 2017 at 7:56 AM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>>> The only thing modern drivers are supposed to do in lastclose is
>>>> restore the fb emulation state. Which is entirely optional, and
>>>> there's really no reason to do that. So restrict it to legacy drivers
>>>> (where the driver cleanup essentially happens in lastclose).
>>>
>>> vga_switcheroo_process_delayed_switch() gets called in lastclose.
>>> Won't that need to get moved elsewhere for this to work?
>>
>> Hm right, I forgot the lazy way to do runtime pm by keeping the device
>> alive as long as anyone has an open fd for it ... This shouldn't be a
>> problem, since you need to unregister from vgaswitcheroo anyway on
>> unload. Maybe that blows up, I'll check the code and augment the patch
>> as needed.
> 
> So I think there's 3 cases:
> - Trying to unload the module. You can't do that while anyone has the
> fd still open, so lastclose is guaranteeed to run.
> - Forcefully unbinding the driver through sysfs. Not any better, since
> the can_switch stuff checks for the open count, and so will delay the
> delayed switch no matter what.

Are you sure that this is working as intended?
https://bugs.freedesktop.org/show_bug.cgi?id=100399 sounds like
unbinding works even while Xorg is using the DRM device.

-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer
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