Re: [PATCH] drm/i915/ilk: Don't attempt to register eDP if LVDS was detected

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Jun 17, 2016 at 06:48:45PM +0300, Imre Deak wrote:
> Atm on ILK we attempt to detect if eDP is present even if LVDS was
> already detected and an encoder for it was registered. This involves
> trying to read out the eDP EDID, which in turn needs the same power
> sequencer that LVDS uses. Poking at the VDD line at an unexpected time
> may or may not interfere with the LVDS panel, but it's probably safer to
> prevent this.  Registering both an LVDS and an eDP connector would also
> present a similar problem accessing the shared PPS at any point later in
> an unexpected way.
> 
> This was caught by CI with the PPS sanity checks in place and the
> initial eDP EDID readout waiting for the panel power cycle timeout
> without the PPS registers being initialized. To solve this latter
> problem move PPS register init earlier before the first use of the
> PPS.
> 
> CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index be08351..fe543d7 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5316,8 +5316,22 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	if (!is_edp(intel_dp))
>  		return true;
>  
> +	/*
> +	 * On ILK we may get here with LVDS already registered. Since the

ILK,SNB,IVB, if you want to accurately list the platforms.

> +	 * driver uses the only internal power sequencer available for both
> +	 * eDP and LVDS bail out early in this case to prevent interfering
> +	 * with an already powered-on LVDS power sequencer.
> +	 */
> +	for_each_intel_encoder(dev, intel_encoder) {
> +		if (intel_encoder->type == INTEL_OUTPUT_LVDS) {
> +			DRM_INFO("LVDS was detected, not registering eDP\n");
> +			return false;
> +		}
> +	}

We could abort much earlier, in the encoder init.

> +
>  	pps_lock(intel_dp);
>  	intel_edp_panel_vdd_sanitize(intel_dp);
> +	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
>  	pps_unlock(intel_dp);

For VLV/CHV we do this stuff in the encoder init already. Maybe we
should move all that stuff here as well?

>  
>  	/* Cache DPCD and EDID for edp. */
> @@ -5334,11 +5348,6 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  		return false;
>  	}
>  
> -	/* We now know it's not a ghost, init power sequence regs. */
> -	pps_lock(intel_dp);
> -	intel_dp_init_panel_power_sequencer_registers(dev, intel_dp);
> -	pps_unlock(intel_dp);
> -
>  	mutex_lock(&dev->mode_config.mutex);
>  	edid = drm_get_edid(connector, &intel_dp->aux.ddc);
>  	if (edid) {
> -- 
> 2.5.0

-- 
Ville Syrjälä
Intel OTC
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