Re: [PATCH v2] drm/i915: Check backlight type while doing eDP backlight initializaiton

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

On Thu, 20 Jun 2019, "Lee, Shawn C" <shawn.c.lee@intel.com> wrote:
> On Wed, 19 Jun 2019, Jani Nikula <jani.nikula@intel.com> wrote:
>>On Wed, 19 Jun 2019, Lee Shawn C <shawn.c.lee@intel.com> wrote:
>>> If LFP backlight type setting from VBT was "VESA eDP AUX Interface".
>>> Driver should check panel capability and try to initialize aux backlight.
>>> No matter i915_modparams.enable_dpcd_backlight was enabled or not.
>>>
>>> v2: access dev_priv->vbt.backlight.type directly and remove unused function.
>>>
>>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> Cc: Jani Nikula <jani.nikula@intel.com>
>>> Cc: Jose Roberto de Souza <jose.souza@intel.com>
>>> Cc: Cooper Chiou <cooper.chiou@intel.com>
>>>
>>> Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>
>>> ---
>>>  drivers/gpu/drm/i915/display/intel_bios.h             | 1 +
>>>  drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c | 4 +++-
>>>  2 files changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_bios.h 
>>> b/drivers/gpu/drm/i915/display/intel_bios.h
>>> index 4e42cfaf61a7..0b7be6389a07 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_bios.h
>>> +++ b/drivers/gpu/drm/i915/display/intel_bios.h
>>> @@ -42,6 +42,7 @@ enum intel_backlight_type {
>>>  	INTEL_BACKLIGHT_DISPLAY_DDI,
>>>  	INTEL_BACKLIGHT_DSI_DCS,
>>>  	INTEL_BACKLIGHT_PANEL_DRIVER_INTERFACE,
>>> +	INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE,
>>>  };
>>>  
>>>  struct edp_power_seq {
>>> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c 
>>> b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>>> index 7ded95a334db..db7c7b9f9b56 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
>>> @@ -264,8 +264,10 @@ intel_dp_aux_display_control_capable(struct 
>>> intel_connector *connector)  int 
>>> intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)  {
>>>  	struct intel_panel *panel = &intel_connector->panel;
>>> +	struct drm_i915_private *dev_priv = 
>>> +to_i915(intel_connector->base.dev);
>>>  
>>> -	if (!i915_modparams.enable_dpcd_backlight)
>>> +	if (!i915_modparams.enable_dpcd_backlight &&
>>> +	    (dev_priv->vbt.backlight.type != 
>>> +INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
>>>  		return -ENODEV;
>>
>>There was also this part in the v1 review:
>>
>>    The usual thing to do is to set i915.enable_dpcd_backlight initial value
>>    to -1 (i.e. make it an int), and with that default value respect
>>    VBT. Otherwise, respect the value of enable_dpcd_backlight.
>>
>>
>>BR,
>>Jani.
>
> Do you mean we should do following?
> 1. Change i915.enable_dpcd_backlight type from bool to int.

Yes.

> 2. Give default value as -1 for enable_dpcd_backlight in i915_param.h.

Yes.

> 3. Add a judgement to check LFP backlight type was aux interface or not.
>    Between if (!i915_modparams.enable_dpcd_backlight) and 
>    if (!intel_dp_aux_display_control_capable(intel_connector)).

Basically replace:

if (!i915_modparams.enable_dpcd_backlight)
	return -ENODEV;

with something like this:

if (i915_modparams.enable_dpcd_backlight == 0 ||
    (i915_modparams.enable_dpcd_backlight == -1 && 
     dev_priv->vbt.backlight.type != INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE))
	return -ENODEV;

i.e. if modparam == -1, use vbt, otherwise use modparam. This lets you
override vbt using the modparam.

You'll still have the capability check below like before.

BR,
Jani.


>
> Best regards,
> Shawn
>
>>>  
>>>  	if (!intel_dp_aux_display_control_capable(intel_connector))
>>
>>--
>>Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center
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