[Intel-gfx] [PATCH] drm/i915: Split pin mapping into per platform functions

[Srivatsa, Anusha]

>-----Original Message-----
>From: Zanoni, Paulo R
>Sent: Monday, August 14, 2017 2:14 PM
>To: Srivatsa, Anusha <anusha.srivatsa at intel.com>; intel-
>gfx at lists.freedesktop.org
>Cc: Vivi, Rodrigo <rodrigo.vivi at intel.com>
>Subject: Re: [Intel-gfx] [PATCH] drm/i915: Split pin mapping into per platform
>functions
>
>Em Qui, 2017-08-10 às 11:42 -0700, Anusha Srivatsa escreveu:
>> Cleanup the code. Map the pins in accordance to individual platforms
>> rather than according to ports.
>> Create separate functions for platforms.
>>
>> v2:
>>  - Add missing condition for CoffeeLake. Make platform
>>  specific functions static. Add function
>>  i915_ddc_pin_mapping().
>>
>> Sugested-by Ville Syrjala <ville.syrjala at linux.intel.com>
>> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>> Cc: Clinton Tayloe <clinton.a.taylor at intel.com>
>> Signed-off-by: Anusha Srivatsa <anusha.srivatsa at intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_hdmi.c | 115
>> ++++++++++++++++++++++++++++++--------
>>  1 file changed, 92 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c
>> b/drivers/gpu/drm/i915/intel_hdmi.c
>> index 2ef1ee85129d..41e6ba01ec1c 100644
>> --- a/drivers/gpu/drm/i915/intel_hdmi.c
>> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
>> @@ -1843,49 +1843,118 @@ void
>> intel_hdmi_handle_sink_scrambling(struct intel_encoder *encoder,
>>  	DRM_DEBUG_KMS("sink scrambling handled\n");
>>  }
>>
>> -static u8 intel_hdmi_ddc_pin(struct drm_i915_private *dev_priv,
>> -			     enum port port)
>> +static u8 chv_ddc_pin_mapping(struct drm_i915_private *dev_priv,
>
>Bikeshedding: what these functions do is pretty much map ports to DDC pins, so
>I'd have named them x_port_to_ddc_pin() since that's the most usual naming
>when converting "units", but I'm not opposed to the current naming. Your choice.
>
>
>> enum port port)
>>  {
>> -	const struct ddi_vbt_port_info *info =
>> -		&dev_priv->vbt.ddi_port_info[port];
>>  	u8 ddc_pin;
>>
>> -	if (info->alternate_ddc_pin) {
>> -		DRM_DEBUG_KMS("Using DDC pin 0x%x for port %c
>> (VBT)\n",
>> -			      info->alternate_ddc_pin,
>> port_name(port));
>> -		return info->alternate_ddc_pin;
>> +	switch (port) {
>> +
>
>This is the only switch statement where you added a blank line at this point. Doing
>this is not our usual coding style.

Will change in the next version.

>
>> +	case PORT_B:
>> +		ddc_pin = GMBUS_PIN_DPB;
>> +		break;
>> +	case PORT_C:
>> +		ddc_pin = GMBUS_PIN_DPC;
>> +		break;
>> +	case PORT_D:
>> +		ddc_pin = GMBUS_PIN_DPD_CHV;
>> +		break;
>> +	default:
>> +		MISSING_CASE(port);
>> +		ddc_pin = GMBUS_PIN_DPB;
>> +		break;
>>  	}
>> +	return ddc_pin;
>
>Another bikeshedding which you don't need to implement: just returning the pins
>inside the switch statements (return GMBUX_PIN_XYZ) without the ddc_pin
>variable would have made the functions much shorter.
>
Hmm... yes. I agree.

>> +}
>> +
>> +static u8 bxt_ddc_pin_mapping(struct drm_i915_private *dev_priv,
>> enum port port)
>> +{
>> +	u8 ddc_pin;
>>
>>  	switch (port) {
>>  	case PORT_B:
>> -		if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv))
>> -			ddc_pin = GMBUS_PIN_1_BXT;
>> -		else
>> -			ddc_pin = GMBUS_PIN_DPB;
>> +		ddc_pin = GMBUS_PIN_1_BXT;
>>  		break;
>>  	case PORT_C:
>> -		if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv))
>> -			ddc_pin = GMBUS_PIN_2_BXT;
>> -		else
>> -			ddc_pin = GMBUS_PIN_DPC;
>> +		ddc_pin = GMBUS_PIN_2_BXT;
>> +		break;
>> +	default:
>> +		MISSING_CASE(port);
>> +		ddc_pin = GMBUS_PIN_DPB;
>
>Now that you've reorganized the code it's very easy to notice that on bxt/cnp the
>default value doesn't even match what we return from port B. I wouldn't
>complain if you addressed this issue in a follow-up patch.
>
Yes. Will change.

>> +		break;
>> +	}
>> +	return ddc_pin;
>> +}
>> +
>> +static u8 cnp_ddc_pin_mapping(struct drm_i915_private *dev_priv,
>> +		enum port port)
>> +{
>> +	u8 ddc_pin;
>> +
>> +	switch (port) {
>> +	case PORT_B:
>> +		ddc_pin = GMBUS_PIN_1_BXT;
>> +		break;
>> +	case PORT_C:
>> +		ddc_pin = GMBUS_PIN_2_BXT;
>>  		break;
>>  	case PORT_D:
>> -		if (HAS_PCH_CNP(dev_priv))
>> -			ddc_pin = GMBUS_PIN_4_CNP;
>> -		else if (IS_CHERRYVIEW(dev_priv))
>> -			ddc_pin = GMBUS_PIN_DPD_CHV;
>> -		else
>> -			ddc_pin = GMBUS_PIN_DPD;
>> +		ddc_pin = GMBUS_PIN_4_CNP;
>> +		break;
>> +	default:
>> +		MISSING_CASE(port);
>> +		ddc_pin = GMBUS_PIN_DPB;
>> +		break;
>> +	}
>> +	return ddc_pin;
>> +}
>> +
>> +static u8 i915_ddc_pin_mapping(struct drm_i915_private *dev_priv,
>> +		enum port port)
>
>The first platform to run this is g4x, so please make the function name start with
>g4x_

I thought having i915_ will make it more readable. But will change to g4x_ in the next version.

>
>> +{
>> +	u8 ddc_pin;
>> +
>> +	switch (port) {
>> +	case PORT_B:
>> +		ddc_pin = GMBUS_PIN_DPB;
>> +		break;
>> +	case PORT_C:
>> +		ddc_pin = GMBUS_PIN_DPC;
>> +		break;
>> +	case PORT_D:
>> +		ddc_pin = GMBUS_PIN_DPD;
>>  		break;
>>  	default:
>>  		MISSING_CASE(port);
>>  		ddc_pin = GMBUS_PIN_DPB;
>>  		break;
>>  	}
>> +	return ddc_pin;
>> +
>> +}
>> +static u8 intel_hdmi_ddc_pin(struct drm_i915_private *dev_priv,
>> +			     enum port port)
>
>Missing blank line between functions.

Will take care in the next version.
>
>> +{
>> +	const struct ddi_vbt_port_info *info =
>> +		&dev_priv->vbt.ddi_port_info[port];
>> +	u8 ddc_pin = 0;

>In our coding style we usually don't zero-initialize things when they don't need to
>be zero-initialized. The advantage of not zero- initializing when we don't need is
>that if some rework happens and we suddenly start forgetting to set a sane value,
>the compiler will tell us.

Got it. Thanks a lot Paulo. 

>
>> +
>> +	if (info->alternate_ddc_pin) {
>> +		DRM_DEBUG_KMS("Using DDC pin 0x%x for port %c
>> (VBT)\n",
>> +			      info->alternate_ddc_pin,
>> port_name(port));
>> +		return info->alternate_ddc_pin;
>> +	}
>> +
>> +	if (IS_CHERRYVIEW(dev_priv))
>> +		ddc_pin = chv_ddc_pin_mapping(dev_priv, port);
>> +	else if (IS_GEN9_LP(dev_priv))
>> +		ddc_pin = bxt_ddc_pin_mapping(dev_priv, port);
>> +	else if (HAS_PCH_CNP(dev_priv))
>> +		ddc_pin = cnp_ddc_pin_mapping(dev_priv, port);
>> +	else
>> +		ddc_pin = i915_ddc_pin_mapping(dev_priv, port);
>
>>  	DRM_DEBUG_KMS("Using DDC pin 0x%x for port %c (platform
>default)\n",
>>  		      ddc_pin, port_name(port));
>> -
>
>Please don't remove this line.

Yes. Will send the next version with changes soon.

Anusha
>
>>  	return ddc_pin;
>>  }
>>