linux-kernel - Re: [PATCH 0/7] Fixes for hybrid graphics Apple machines

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Date:	Fri, 7 Sep 2012 22:35:04 +0100
From:	Dave Airlie <airlied@...il.com>
To:	Seth Forshee <seth.forshee@...onical.com>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	David Airlie <airlied@...ux.ie>,
	Matthew Garrett <mjg@...hat.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Andreas Heider <andreas@...tr.de>
Subject: Re: [PATCH 0/7] Fixes for hybrid graphics Apple machines

On Fri, Sep 7, 2012 at 4:22 PM, Seth Forshee <seth.forshee@...onical.com> wrote:
> Many hybrid graphics Apple laptops fail to set up LVDS on the secondary
> GPU due to missing or incorrect mode information for the panel at init
> time. The only way to get the LVDS mode on these machines is via the
> DDC, but this is muxed to the active GPU at boot. However, the graphics
> mux on these machines supports muxing the i2c idependently of the
> display, making it possible for the secondary graphics driver to read
> the EDID without a full display switch.
>
> In order to support this, these patches modify vga_switcheroo to allow
> muxing of the DDC idependently of the display. apple-gmux is updated to
> support this new functionality, and drm_get_edid() is modified to switch
> the DDC mux as needed.
>
> For this to work we also need to ensure that sufficient switcheroo
> suport is available before initializing the secondary GPU. This is done
> by adding any non-active GPUs that try to initialize before switcheroo
> is ready to a list and initializing these devices once switcheroo
> becomes ready. This behavior is restricted to Apple laptops to prevent
> causing problems on other machines.

I hate this idea, no delaying stuff. We either need to have some sort
of enforced ordering or make some stuff only work built-in.

But sticking things on a delayed list just in case seems wrong to me.

Dave.
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