linux-kernel - Re: [Intel-gfx] [PATCH 05/21] drm/i915: Check eDP power when doing aux channel communications

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Message-ID: <20111003134818.0ef811ce@jbarnes-desktop>
Date:	Mon, 3 Oct 2011 13:48:18 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Keith Packard <keithp@...thp.com>
Cc:	Dave Airlie <airlied@...hat.com>, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH 05/21] drm/i915: Check eDP power when doing
 aux channel communications

On Thu, 29 Sep 2011 18:09:37 -0700
Keith Packard <keithp@...thp.com> wrote:

> Verify that the eDP VDD is on, either with the panel being on or with
> the VDD force-on bit being set.
> 
> This demonstrates that in many instances, VDD is not on when needed,
> which leads to failed EDID communications.
> 
> Signed-off-by: Keith Packard <keithp@...thp.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c |   22 ++++++++++++++++++++++
>  1 files changed, 22 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 8ab2a88..3b29a6f 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -279,6 +279,24 @@ intel_hrawclk(struct drm_device *dev)
>  	}
>  }
>  
> +static void
> +intel_dp_check_edp(struct intel_dp *intel_dp)
> +{
> +	struct drm_device *dev = intel_dp->base.base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	u32 pp_status, pp_control;
> +	if (!is_edp(intel_dp))
> +		return;
> +	pp_status = I915_READ(PCH_PP_STATUS);
> +	pp_control = I915_READ(PCH_PP_CONTROL);
> +	if ((pp_status & PP_ON) == 0 && (pp_control & EDP_FORCE_VDD) == 0) {
> +		WARN(1, "eDP powered off while attempting aux channel communication.\n");
> +		DRM_DEBUG_KMS("Status 0x%08x Control 0x%08x\n",
> +			      pp_status,
> +			      I915_READ(PCH_PP_CONTROL));
> +	}
> +}

I'd call it "intel_dp_assert_dp_power" or something more descriptive
(or just assert_panel_power to match the other asserts in
intel_display.c), but other than that this is a nice sanity check.

-- 
Jesse Barnes, Intel Open Source Technology Center
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