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SubjectRe: [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@keithp.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@keithp.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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