Re: [Intel-gfx] [PATCH] drm/i915/display: Warn about types of backlight not handled

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 25 Nov 2020, Imre Deak <imre.deak@intel.com> wrote:
> On Fri, Nov 20, 2020 at 11:57:48AM -0800, José Roberto de Souza wrote:
>> Right now we are only explicitly handling the backlight of types
>> INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE, INTEL_BACKLIGHT_DSI_DCS and
>> INTEL_BACKLIGHT_DISPLAY_DDI all others are being handled as
>> INTEL_BACKLIGHT_DISPLAY_DDI(south display engine PWM) but that
>> might not be the intended HW usage, so lets warn to identify those
>> systems and implement it properly if needed.
>> 
>> Cc: Imre Deak <imre.deak@intel.com>
>> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_panel.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
>> index 9f23bac0d792..368722536462 100644
>> --- a/drivers/gpu/drm/i915/display/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/display/intel_panel.c
>> @@ -2023,6 +2023,21 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
>>  	struct intel_connector *connector =
>>  		container_of(panel, struct intel_connector, panel);
>>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>> +	enum intel_backlight_type type = dev_priv->vbt.backlight.type;
>> +
>> +	if (dev_priv->params.enable_dpcd_backlight)
>> +		type = INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE;

The default is -1, so this might screw up the init.

>> +
>> +	drm_dbg_kms(&dev_priv->drm,
>> +		    "Connector %s backlight type %u controller %u\n",
>> +		    connector->base.name, type,
>> +		    dev_priv->vbt.backlight.controller);
>> +
>> +	if (type != INTEL_BACKLIGHT_DISPLAY_DDI &&
>> +	    type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE &&
>> +	    type != INTEL_BACKLIGHT_DSI_DCS)
>> +		drm_warn(&dev_priv->drm, "Backlight type %i not properly handled\n",
>> +			 type);
>
> Not sure about the history/current state of VBT errors wrt. the
> backlight type and so this may generate a lot of bug reports without an
> actual problem. A backlight problem would be anyway visible, so
> we'd get a report and then we could just use the previous debug print
> you added. It could be added to the relevant debug print in 
> intel_panel_setup_backlight().

I think I'd settle for a debug print too.

BR,
Jani.

>
> +Jani.
>
>>  
>>  	if (connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
>>  	    intel_dp_aux_init_backlight_funcs(connector) == 0)
>> -- 
>> 2.29.2
>> 
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-- 
Jani Nikula, Intel Open Source Graphics Center
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