[Intel-gfx] [PATCH v3 1/3] drm/i915/ibx, cpt: Don't attempt to register eDP if LVDS was detected

[Ville Syrjälä]

On Tue, Jun 21, 2016 at 11:51:47AM +0300, Imre Deak wrote:
> Atm on IBX/CPT 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 DPCD, 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.
> 
> We also need this to be able fix PPS initialization before its first use
> in the next patch. For that we want to be sure that PPS is not in use
> by LVDS.
> 
> v2:
> - Split out the PPS init fix to a separate patch. (Chris)
> - Add comment about eDP init depending on LVDS init. (Chris)
> - Make the use of the intel_encoder ptr less error prone.
> v3:
> - Use IBX/CPT reference instead of the incorrect ILK, add a WARN about
>   this. (Ville)
> 
> CC: Ville Syrjälä <ville.syrjala at linux.intel.com>
> CC: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk> (v2)
> ---
>  drivers/gpu/drm/i915/intel_display.c |  5 +++++
>  drivers/gpu/drm/i915/intel_dp.c      | 17 +++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 0b2cd66..1141b86 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -14710,6 +14710,11 @@ static void intel_setup_outputs(struct drm_device *dev)
>  	struct intel_encoder *encoder;
>  	bool dpd_is_edp = false;
>  
> +	/*
> +	 * intel_edp_init_connector() depends on this completing first, to
> +	 * prevent the registeration of both eDP and LVDS and the incorrect
> +	 * sharing of the PPS.
> +	 */
>  	intel_lvds_init(dev);
>  
>  	if (intel_crt_present(dev))
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index ffa43ec..9a1cef4 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5303,6 +5303,7 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
>  	struct intel_encoder *intel_encoder = &intel_dig_port->base;
>  	struct drm_device *dev = intel_encoder->base.dev;
> +	struct intel_encoder *tmp_encoder;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_display_mode *fixed_mode = NULL;
>  	struct drm_display_mode *downclock_mode = NULL;
> @@ -5314,6 +5315,22 @@ static bool intel_edp_init_connector(struct intel_dp *intel_dp,
>  	if (!is_edp(intel_dp))
>  		return true;
>  
> +	/*
> +	 * On IBX/CPT we may get here with LVDS already registered. Since the
> +	 * 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, tmp_encoder) {
> +		if (tmp_encoder->type != INTEL_OUTPUT_LVDS)
> +			continue;
> +
> +		WARN_ON(!(HAS_PCH_IBX(dev_priv) || HAS_PCH_CPT(dev_priv)));

I think I usually prefer '!A && !B' for whatever reason. Either works.

> +		DRM_INFO("LVDS was detected, not registering eDP\n");
> +
> +		return false;
> +	}

I would have probably stuffed the loop into a small helper
(eg. has_lvds_encoder() or something along those lines). But
this works too, so

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> +
>  	pps_lock(intel_dp);
>  	intel_edp_panel_vdd_sanitize(intel_dp);
>  	pps_unlock(intel_dp);
> -- 
> 2.5.0

-- 
Ville Syrjälä
Intel OTC