Re: [PATCH] drm/i915/vbt: Assume port A is connected to eDP when there's no VBT

From: Jani Nikula <jani.nikula@intel.com>
To: "Pandiyan, Dhinakaran" <dhinakaran.pandiyan@intel.com>,
	"Navare, Manasi D" <manasi.d.navare@intel.com>
Cc: "intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"Vivi, Rodrigo" <rodrigo.vivi@intel.com>
Subject: Re: [PATCH] drm/i915/vbt: Assume port A is connected to eDP	when there's no VBT
Date: Thu, 10 Aug 2017 22:45:51 +0300	[thread overview]
Message-ID: <87378zjjf4.fsf@intel.com> (raw)
In-Reply-To: <1502393365.28740.74.camel@dk-H97M-D3H>

On Thu, 10 Aug 2017, "Pandiyan, Dhinakaran" <dhinakaran.pandiyan@intel.com> wrote:
> On Thu, 2017-08-10 at 05:47 +0000, Navare, Manasi D wrote:
>> We currently assume port A is connected to a DP sink when VBT is absent, instead assume it is connected to an eDP sink, which seems like a more common configuration. Although I don't have data to back this up, it is still just as valid as asumming port A is not eDP. This reverts to the behavior before a98d9c1 ("drm/i915/ddi: Rely on VBT DDI port info for eDP detection") except only when there is no VBT. Knowing whether a panel is eDP or not from the panel itself would have been nicer, but I cannot find any DPCD registers that provide this reliably.
>> 
>> Cc: Jani Nikula <jani.nikula@intel.com>
>> Cc: Imre Deak <imre.deak@intel.com>
>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> Cc: Clint Taylor <clinton.a.taylor@intel.com>
>> 
>> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>> 
>> Is this patch trying to fix a specific bug? 
>
> Yes, we have a platform without vbt that has an eDP.
>
>> Where do you plan to use supports_edp flag? 
>
> No plans, this is not a new flag. The vbt info is used when when dp
> connectors are initialized.
>
>> I guess I am trying to understand the need for this in the vbt missing defaults and what this patch is trying to solve here. 
>
> Assuming port A is not connected an eDP display when it actually is
> messes up connector status detection. 

This might be a reasonable default assumption.

Regardless, please have a look at [1]; I seem to have forgotten to push
it... could use a tested-by. :)

BR,
Jani.

[1] http://patchwork.freedesktop.org/patch/msgid/20170531151739.26500-1-jani.nikula@intel.com

>
>
>> 
>> Manasi
>> 
>> 
>> ---
>>  drivers/gpu/drm/i915/intel_bios.c | 1 +
>>  1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
>> index 82b144c..89a405e 100644
>> --- a/drivers/gpu/drm/i915/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/intel_bios.c
>> @@ -1403,6 +1403,7 @@ init_vbt_missing_defaults(struct drm_i915_private *dev_priv)
>>  		info->supports_dvi = (port != PORT_A && port != PORT_E);
>>  		info->supports_hdmi = info->supports_dvi;
>>  		info->supports_dp = (port != PORT_E);
>> +		info->supports_edp = (port == PORT_A);
>> 
>>  	}
>>  }
>>  
>> --
>> 2.7.4
>> 
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-- 
Jani Nikula, Intel Open Source Technology Center
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