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

[Imre Deak <imre.deak@intel.com>]

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.

--Imre

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