linux-kernel - Re: [PATCH 1/2] drm/i915: Revert wait for vblank to prevent X refresh issues

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Message-ID: <20100824093939.3166fa8a@virtuousgeek.org>
Date:	Tue, 24 Aug 2010 09:39:39 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Sitsofe Wheeler <sitsofe@...oo.com>
Cc:	intel-gfx@...ts.freedesktop.org,
	Chris Wilson <chris@...is-wilson.co.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] drm/i915: Revert wait for vblank to prevent X
 refresh issues

On Tue, 24 Aug 2010 16:53:59 +0100
Sitsofe Wheeler <sitsofe@...oo.com> wrote:

> In commit 9d0498a2bf7455159b317f19531a3e5db2ecc9c4 20ms waits were
> converted into vblank waits. One of these caused tearing, mode detection
> and redraw issues on an EeePC 900 with a more recent intel userspace (
> http://lkml.org/lkml/2010/8/23/432 ). Restoring the 20ms wait resolves
> the issue.
> 
> Signed-off-by: Sitsofe Wheeler <sitsofe@...oo.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 23157e1..116d938 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4539,7 +4539,7 @@ struct drm_crtc *intel_get_load_detect_pipe(struct intel_encoder *intel_encoder,
>  		encoder_funcs->commit(encoder);
>  	}
>  	/* let the connector get through one full cycle before testing */
> -	intel_wait_for_vblank(dev, intel_crtc->pipe);
> +	msleep(20);
>  
>  	return crtc;
>  }

Wow, tearing, mode detection and redraw problems all because of this
line?  Maybe because we wait for a longer period here now?  Can you
check and see if we're timing out in the wait_for_vblank function?

-- 
Jesse Barnes, Intel Open Source Technology Center
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