[Intel-gfx] [PATCH] drm/i915/bios: gracefully disable dual eDP for now

[Ville Syrjälä]

On Tue, Oct 05, 2021 at 08:56:36PM +0300, Jani Nikula wrote:
> For the time being, neither the power sequencer nor the backlight code
> properly support two eDP panels simultaneously. While the software
> states will be independent, the same sets of registers will be used for
> both eDP panels, clobbering the hardware state and leading to errors.
> 
> Gracefully disable dual eDP until proper support has been added.
> 
> Cc: José Roberto de Souza <jose.souza at intel.com>
> Cc: Uma Shankar <uma.shankar at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Swati Sharma <swati2.sharma at intel.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bios.c | 47 +++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index f9776ca85de3..b99907c656bb 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -1930,6 +1930,50 @@ static int _intel_bios_max_tmds_clock(const struct intel_bios_encoder_data *devd
>  	}
>  }
>  
> +static enum port get_edp_port(struct drm_i915_private *i915)
> +{
> +	const struct intel_bios_encoder_data *devdata;
> +	enum port port;
> +
> +	for_each_port(port) {
> +		devdata = i915->vbt.ports[port];
> +
> +		if (devdata && intel_bios_encoder_supports_edp(devdata))
> +			return port;
> +	}
> +
> +	return PORT_NONE;
> +}
> +
> +/*
> + * FIXME: The power sequencer and backlight code currently do not support more
> + * than one set registers, at least not on anything other than VLV/CHV. It will
> + * clobber the registers. As a temporary workaround, gracefully prevent more
> + * than one eDP from being registered.
> + */
> +static void sanitize_dual_edp(struct intel_bios_encoder_data *devdata,
> +			      enum port port)
> +{
> +	struct drm_i915_private *i915 = devdata->i915;
> +	struct child_device_config *child = &devdata->child;
> +	enum port p;
> +
> +	/* CHV might not clobber PPS registers. */
> +	if (IS_CHERRYVIEW(i915))

vlv and chv should both behave identically. At least I don't remember
any single eDP assumptions in the code for either.

Hmm. Quick glance suggest bxt/glk should handle this correctly
as well? But the more recent platforms are certainly borked.
Well, that's assuming the vbt related bits are correct for bxt/glk.

> +		return;
> +
> +	p = get_edp_port(i915);
> +	if (p == PORT_NONE)
> +		return;
> +
> +	drm_dbg_kms(&i915->drm, "both ports %c and %c configured as eDP, "
> +		    "disabling port %c eDP\n", port_name(p), port_name(port),
> +		    port_name(port));
> +
> +	child->device_type &= ~DEVICE_TYPE_DISPLAYPORT_OUTPUT;
> +	child->device_type &= ~DEVICE_TYPE_INTERNAL_CONNECTOR;
> +}
> +
>  static bool is_port_valid(struct drm_i915_private *i915, enum port port)
>  {
>  	/*
> @@ -1987,6 +2031,9 @@ static void parse_ddi_port(struct drm_i915_private *i915,
>  		    supports_typec_usb, supports_tbt,
>  		    devdata->dsc != NULL);
>  
> +	if (is_edp)
> +		sanitize_dual_edp(devdata, port);
> +
>  	if (is_dvi)
>  		sanitize_ddc_pin(devdata, port);
>  
> -- 
> 2.30.2

-- 
Ville Syrjälä
Intel