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

Jani Nikula
2017-08-10T19:45:58Z

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