linux-kernel - Re: [Intel-gfx] Linux 3.16-rc2

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Message-ID: <20140630100925.GA18836@nuc-i3427.alporthouse.com>
Date:	Mon, 30 Jun 2014 11:09:25 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Pavel Machek <pavel@....cz>
Cc:	Thomas Meyer <thomas@...3r.de>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jikos@...e.cz
Subject: Re: [Intel-gfx] Linux 3.16-rc2

On Mon, Jun 30, 2014 at 12:02:20PM +0200, Pavel Machek wrote:
> On Tue 2014-06-24 13:27:37, Chris Wilson wrote:
> > On Tue, Jun 24, 2014 at 02:24:30PM +0200, Thomas Meyer wrote:
> > > Am Dienstag, den 24.06.2014, 12:57 +0100 schrieb Chris Wilson:
> > > > On Tue, Jun 24, 2014 at 02:06:24PM +0300, Jani Nikula wrote:
> > > > > On Tue, 24 Jun 2014, Thomas Meyer <thomas@...3r.de> wrote:
> > > > > > the i915 driver is still broken in 3.16-rc2. Resume from ram crashes the
> > > > > > X server.
> > > > > 
> > > > > This is not new to 3.16-rc2; apparently we've had it since v3.15-rc4
> > > > > [1]. Also related [2].
> > > > > 
> > > > > Chris, any fresh ideas?
> > > > 
> > > > Nope. The bug is https://bugs.freedesktop.org/show_bug.cgi?id=76554
> > > > everything we know and have tried is there. Which is not much more than
> > > > at time of the original incarnation:
> > > > 
> > > > commit 50aa253d820ad4577e2231202f2c8fd89f9dc4e6
> > > > Author: Keith Packard <keithp@...thp.com>
> > > > Date:   Tue Oct 14 17:20:35 2008 -0700
> > > > 
> > > >     i915: Fix up ring initialization to cover G45 oddities
> > > >     
> > > >     G45 appears quite sensitive to ring initialization register writes,
> > > >     sometimes leaving the HEAD register with the START register contents. Check
> > > >     to make sure HEAD is reset correctly when START is written, and fix it up,
> > > >     screaming loudly.
> > > > -Chris
> > > > 
> > > 
> > > Hi,
> > > 
> > > so why not revert 78f2975eec9faff353a6194e854d3d39907bab68 (drm/i915:
> > > Move all ring resets before setting the HWS page) ?
> > 
> > Because that patch was in response to a boot time regression.
> 
> It seems we are in a fairly ugly "fix one board, it breaks another" iterations, right?
> 
> (BTW, if you apply patch to fix this bug, could you Cc me? I have strange feeling
> that it will break my setup... Actually, it probably makes sense to Cc all the people
> who reported problems with ring initialization...
> 
> What patch caused the boot time regression you are talking about? We need to get 
> list of commits involved in this, and revert the original one...

commit 9991ae787a0c87fe7c783b4b6f4754c3cdbb6213
Author: Chris Wilson <chris@...is-wilson.co.uk>
Date:   Wed Apr 2 16:36:07 2014 +0100

    drm/i915: Move all ring resets before setting the HWS page
    
    In commit a51435a3137ad8ae75c288c39bd2d8b2696bae8f
    Author: Naresh Kumar Kachhi <naresh.kumar.kachhi@...el.com>
    Date:   Wed Mar 12 16:39:40 2014 +0530
    
        drm/i915: disable rings before HW status page setup
    
    we reordered stopping the rings to do so before we set the HWS register.
    However, there is an extra workaround for g45 to reset the rings twice,
    and for consistency we should apply that workaround before setting the
    HWS to be sure that the rings are truly stopped.
    
    Cc: Naresh Kumar Kachhi <naresh.kumar.kachhi@...el.com>
    Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
    Reviewed-by: Jesse Barnes <jbarnes@...tuousgeek.org>
    Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>


commit a51435a3137ad8ae75c288c39bd2d8b2696bae8f
Author: Naresh Kumar Kachhi <naresh.kumar.kachhi@...el.com>
Date:   Wed Mar 12 16:39:40 2014 +0530

    drm/i915: disable rings before HW status page setup
    
    Rings should be idle before issuing sync_flush
    (in intel_ring_setup_status_page). This patch moves the ring
    disabling before doing the HW status page setup.
    
    Signed-off-by: Naresh Kumar Kachhi <naresh.kumar.kachhi@...el.com>
    Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
    Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>


-- 
Chris Wilson, Intel Open Source Technology Centre
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