Re: [PATCH] drm/i915/cnl: Map VBT DDC Pin to BSpec DDC Pin.

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 19 Oct 2017, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
> Starting on CNL we now need to map VBT DDC Pin to
> BSPec DDC Pin values. Not a direct translation anymore.
>
> According to VBT
> Block 2 (General Bytes Definition)
> DDC Bus
>
> +----------+-----------+--------------------+
> | DDI Type | VBT Value | Bspec Mapped Value |
> +----------+-----------+--------------------+
> | DDI-B    | 0x1       | 0x1                |
> | DDI-C    | 0x2       | 0x2                |
> | DDI-D    | 0x3       | 0x4                |
> | DDI-F    | 0x4       | 0x3                |
> +----------+-----------+--------------------+
>
> v2: Move defines to a better place.
>     This is actually CNL_PCH not CNL only.
> v3: Accepting Ville's suggestions: enums and array to
>     to make this future proof.
>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> Cc: Clinton Taylor <clinton.a.taylor@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_bios.c     | 26 ++++++++++++++++----------
>  drivers/gpu/drm/i915/intel_vbt_defs.h | 15 +++++++++++++++
>  2 files changed, 31 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index dc4fad30bf4f..79638308664c 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -1071,6 +1071,21 @@ static void sanitize_aux_ch(struct drm_i915_private *dev_priv,
>  	}
>  }
>  
> +static const enum bspec_gmbus_pin cnp_ddc_pin_map[] = {
> +	[DDC_BUS_DDI_B] = GMBUS_PIN_1,
> +	[DDC_BUS_DDI_C] = GMBUS_PIN_2,
> +	[DDC_BUS_DDI_D] = GMBUS_PIN_4,
> +	[DDC_BUS_DDI_F] = GMBUS_PIN_3,

I think the two last lines deserve comments like /* sic */ or something.

> +};
> +
> +static u8 get_ddc_pin(struct drm_i915_private *dev_priv, u8 vbt_pin)

Nitpick, You're passing in a pin and you get a pin? How about
"map_ddc_pin"? Like your array name suggests?

> +{
> +	if (HAS_PCH_CNP(dev_priv))
> +		return cnp_ddc_pin_map[vbt_pin];
> +
> +	return vbt_pin;
> +}
> +
>  static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
>  			   u8 bdb_version)
>  {
> @@ -1164,16 +1179,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv, enum port port,
>  		DRM_DEBUG_KMS("Port %c is internal DP\n", port_name(port));
>  
>  	if (is_dvi) {
> -		info->alternate_ddc_pin = ddc_pin;
> -
> -		/*
> -		 * All VBTs that we got so far for B Stepping has this
> -		 * information wrong for Port D. So, let's just ignore for now.
> -		 */
> -		if (IS_CNL_REVID(dev_priv, CNL_REVID_B0, CNL_REVID_B0) &&
> -		    port == PORT_D) {
> -			info->alternate_ddc_pin = 0;
> -		}
> +		info->alternate_ddc_pin = get_ddc_pin(dev_priv, ddc_pin);
>  
>  		sanitize_ddc_pin(dev_priv, port);
>  	}
> diff --git a/drivers/gpu/drm/i915/intel_vbt_defs.h b/drivers/gpu/drm/i915/intel_vbt_defs.h
> index 7e2a96712d07..dfc9f7a43668 100644
> --- a/drivers/gpu/drm/i915/intel_vbt_defs.h
> +++ b/drivers/gpu/drm/i915/intel_vbt_defs.h
> @@ -308,6 +308,21 @@ struct bdb_general_features {
>  
>  #define LEGACY_CHILD_DEVICE_CONFIG_SIZE		33
>  
> +/* DDC Bus DDI Type 155+ */
> +enum vbt_gmbus_ddi {
> +	DDC_BUS_DDI_B = 0x1,
> +	DDC_BUS_DDI_C,
> +	DDC_BUS_DDI_D,
> +	DDC_BUS_DDI_F,
> +};
> +
> +enum bspec_gmbus_pin {
> +	GMBUS_PIN_1 = 0x1,
> +	GMBUS_PIN_2,
> +	GMBUS_PIN_3,
> +	GMBUS_PIN_4,

You already have these defined in i915_reg.h. The naming isn't pretty,
but the above doesn't make much sense either.

> +};
> +
>  /*
>   * The child device config, aka the display device data structure, provides a
>   * description of a port and its configuration on the platform.

-- 
Jani Nikula, Intel Open Source Technology Center
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