linux-kernel - Re: [PATCH] DRM / i915: Fix resume regression on MSI Wind U100 w/o KMS

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Message-Id: <201001090121.37368.rjw@sisk.pl>
Date:	Sat, 9 Jan 2010 01:21:37 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Eric Anholt <eric@...olt.net>,
	Zhenyu Wang <zhenyuw@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	dri-devel@...ts.sourceforge.net
Subject: Re: [PATCH] DRM / i915: Fix resume regression on MSI Wind U100 w/o KMS

On Saturday 09 January 2010, Linus Torvalds wrote:
> 
> On Sat, 9 Jan 2010, Rafael J. Wysocki wrote:
> >
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > Commit cbda12d77ea590082edb6d30bd342a67ebc459e0 (drm/i915: implement
> > new pm ops for i915), among other things, removed the .suspend and
> > .resume pointers from the struct drm_driver object in i915_drv.c,
> > which broke resume without KMS on my MSI Wind U100.
> > 
> > Fix this by reverting that part of commit cbda12d77ea59.
> 
> Hmm. I get the feeling that perhaps the of the drm_driver callbacks was 
> very muchintentional, and that the code presumably wants to be called 
> purely through the PCI layer, and not through the "drm class" logic at 
> all?
> 
> Your patch seems like it would always execute the silly class suspend even 
> though we explicitly don't want to. And a much nicer fix would seem to 
> register the thing properly as a PCI driver even if you don't then use 
> KMS.
> 
> So it looks to me like the problem is that drm_init() will register the 
> driver as a real PCI driver only if
> 
> 	driver->driver_features & DRIVER_MODESET
> 
> and otherwise it does that very odd "stealth mode manual scanning" thing 
> which doesn't register it as a proper PCI driver.
> 
> So could we instead make that "disable KSM" _just_ disable the mode 
> setting part, not disable the "I'm a real driver" part?

Hmm.  Do you mean set DRIVER_MODESET unconditionally before calling drm_init()
and only reset it later if necessary?

Rafael
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