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

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Message-ID: <alpine.LNX.2.00.1407081445310.1655@pobox.suse.cz>
Date:	Tue, 8 Jul 2014 14:46:57 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Chris Wilson <chris@...is-wilson.co.uk>
cc:	Thomas Meyer <thomas@...3r.de>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Intel-gfx] Linux 3.16-rc2

On Tue, 8 Jul 2014, Chris Wilson wrote:

> > I actually tried to introduce rather large delays between individual 
> > I915_WRITE() calls in the ring initialization sequence a couple weeks ago 
> > already, but it resulted in complete machine lockup (which is worse than 
> > my usual symptoms) during resume. Therefore I probably lack the knowledge 
> > of internal workings of the HW that would allow me to guess what the 
> > reasonable timeout value should be.
> > 
> > Willing to test any patches.
> 
> Are you using the extra patches on bug 76554? If not, try

Just for debugging.

> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index e18ed05dc0d5..48326f9628d4 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -526,6 +526,9 @@ static int init_ring_common(struct intel_engine_cs *ring)
>                         ((ringbuf->size - PAGE_SIZE) & RING_NR_PAGES)
>                         | RING_VALID);
>  
> +       I915_WRITE_HEAD(ring, 0);
> +       (void)I915_READ_HEAD(ring);
> +
>         /* If the head is still not zero, the ring is dead */
>         if (wait_for((I915_READ_CTL(ring) & RING_VALID) != 0 &&
>                      I915_READ_START(ring) == i915_gem_obj_ggtt_offset(obj) &&

Tried on top of current Linus' tree, and no improvement. ring 
initialization failure upon resume, and window redrawing hosed.

-- 
Jiri Kosina
SUSE Labs
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