Re: [PATCH] drm/i915/bxt: WA for swapped HPD pins in A stepping

["Jindal, Sonika" <sonika.jindal@intel.com>]

On 7/18/2015 5:17 AM, Imre Deak wrote:
> On Fri, 2015-07-17 at 13:47 +0530, Sonika Jindal wrote:
>> As per bspec, on BXT A0/A1, sw needs to activate DDIA HPD logic
>> and interrupts to check the external panel connection and DDIC HPD
>> logic for edp panel.
>>
>> v2: For DP, irq_port is used to determine the encoder instead of
>> hpd_pin and removing the edp HPD logic because port A HPD is not
>> present(Imre)
>>
>> Signed-off-by: Sonika Jindal <sonika.jindal@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_ddi.c  |   10 +++++++++-
>>   drivers/gpu/drm/i915/intel_hdmi.c |    9 ++++++++-
>>   2 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
>> index e2c6f73..777e3a3 100644
>> --- a/drivers/gpu/drm/i915/intel_ddi.c
>> +++ b/drivers/gpu/drm/i915/intel_ddi.c
>> @@ -3225,7 +3225,15 @@ void intel_ddi_init(struct drm_device *dev, enum port port)
>>   			goto err;
>>
>>   		intel_dig_port->hpd_pulse = intel_dp_hpd_pulse;
>> -		dev_priv->hotplug.irq_port[port] = intel_dig_port;
>> +		/*
>> +		 * On BXT A0/A1, sw needs to activate DDIA HPD logic and
>> +		 * interrupts to check the external panel connection.
>> +		 */
>> +		if (IS_BROXTON(dev_priv) && (INTEL_REVID(dev) < BXT_REVID_B0)
>> +					 && port == PORT_B)
>> +			dev_priv->hotplug.irq_port[PORT_A] = intel_dig_port;
>
> This happens to work but is confusing. irq_port[PORT_A] will be set here
> already and the above will simply overwrite it without explanation. I
> would also handle the port == PORT_A case and not set irq_port for it.
>
> The same swapping for hpd_pin is missing from intel_dp_init_connector().
>
>> +		else
>> +			dev_priv->hotplug.irq_port[port] = intel_dig_port;
>>   	}
>>
>>   	/* In theory we don't need the encoder->type check, but leave it just in
>> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
>> index 70bad5b..94fa716 100644
>> --- a/drivers/gpu/drm/i915/intel_hdmi.c
>> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
>> @@ -1973,7 +1973,14 @@ void intel_hdmi_init_connector(struct intel_digital_port *intel_dig_port,
>>   			intel_hdmi->ddc_bus = GMBUS_PIN_1_BXT;
>>   		else
>>   			intel_hdmi->ddc_bus = GMBUS_PIN_DPB;
>> -		intel_encoder->hpd_pin = HPD_PORT_B;
>> +		/*
>> +		 * On BXT A0/A1, sw needs to activate DDIA HPD logic and
>> +		 * interrupts to check the external panel connection.
>> +		 */
>> +		if (IS_BROXTON(dev_priv) && (INTEL_REVID(dev) < BXT_REVID_B0))
>> +			intel_encoder->hpd_pin = HPD_PORT_A;
>> +		else
>> +			intel_encoder->hpd_pin = HPD_PORT_B;
>>   		break;
>>   	case PORT_C:
>>   		if (IS_BROXTON(dev_priv))
>
> As I earlier pointed out with the above approach, you need to add
> support for HPD events on the HPD_PORT_A pin. If you look at the
> for_each_hpd_pin() macro and intel_hpd_irq_handler()/is_dig_port you'll
> notice that any interrupt event on the HPD_PORT_A pin will be ignored
> now.
Hmm :(. For now, we can fix for_each_hpd_pin and add a check in 
intel_hpd_pin_to_port to return PORT_B for pin 0 if A0/A1. Then we can 
skip the check in intel_ddi_init. But this again will look very confusing.

So two options:
1. We move back to the older approach where we just use another hpd 
ports array in i915_irq.c
2. Go with current approach.

I feel option 1 is more clean and less prone to further issues.
What do you suggest?

Regards,
Sonika
>
> --Imre
>
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