Re: [PATCH] drm/i915/bios: use a flag for vbt hdmi level shift presence

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

On Tue, 05 Nov 2019, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> On Tue, Nov 05, 2019 at 03:39:00PM +0200, Jani Nikula wrote:
>> The pre-initialized magic value is a bit silly, switch to a flag
>> instead. While at it, clean up the validity checks. No functional
>> changes apart from the added checks.
>> 
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_bios.c | 10 +---------
>>  drivers/gpu/drm/i915/display/intel_ddi.c  | 19 +++++++++++--------
>>  drivers/gpu/drm/i915/i915_drv.h           |  8 ++------
>>  3 files changed, 14 insertions(+), 23 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
>> index a03f56b7b4ef..c19b234bebe6 100644
>> --- a/drivers/gpu/drm/i915/display/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
>> @@ -1509,6 +1509,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv,
>>  			      port_name(port),
>>  			      hdmi_level_shift);
>>  		info->hdmi_level_shift = hdmi_level_shift;
>> +		info->hdmi_level_shift_set = true;
>>  	}
>>  
>>  	if (bdb_version >= 204) {
>> @@ -1692,8 +1693,6 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
>>  static void
>>  init_vbt_defaults(struct drm_i915_private *dev_priv)
>>  {
>> -	enum port port;
>> -
>>  	dev_priv->vbt.crt_ddc_pin = GMBUS_PIN_VGADDC;
>>  
>>  	/* Default to having backlight */
>> @@ -1721,13 +1720,6 @@ init_vbt_defaults(struct drm_i915_private *dev_priv)
>>  	dev_priv->vbt.lvds_ssc_freq = intel_bios_ssc_frequency(dev_priv,
>>  			!HAS_PCH_SPLIT(dev_priv));
>>  	DRM_DEBUG_KMS("Set default to SSC at %d kHz\n", dev_priv->vbt.lvds_ssc_freq);
>> -
>> -	for_each_port(port) {
>> -		struct ddi_vbt_port_info *info =
>> -			&dev_priv->vbt.ddi_port_info[port];
>> -
>> -		info->hdmi_level_shift = HDMI_LEVEL_SHIFT_UNKNOWN;
>> -	}
>>  }
>>  
>>  /* Defaults to initialize only if there is no VBT. */
>> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
>> index c91521bcf06a..ec51f6971b16 100644
>> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
>> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
>> @@ -888,11 +888,10 @@ icl_get_combo_buf_trans(struct drm_i915_private *dev_priv, int type, int rate,
>>  
>>  static int intel_ddi_hdmi_level(struct drm_i915_private *dev_priv, enum port port)
>>  {
>> +	struct ddi_vbt_port_info *port_info = &dev_priv->vbt.ddi_port_info[port];
>>  	int n_entries, level, default_entry;
>>  	enum phy phy = intel_port_to_phy(dev_priv, port);
>>  
>> -	level = dev_priv->vbt.ddi_port_info[port].hdmi_level_shift;
>> -
>>  	if (INTEL_GEN(dev_priv) >= 12) {
>>  		if (intel_phy_is_combo(dev_priv, phy))
>>  			icl_get_combo_buf_trans(dev_priv, INTEL_OUTPUT_HDMI,
>> @@ -927,14 +926,18 @@ static int intel_ddi_hdmi_level(struct drm_i915_private *dev_priv, enum port por
>>  		return 0;
>>  	}
>>  
>> -	/* Choose a good default if VBT is badly populated */
>> -	if (level == HDMI_LEVEL_SHIFT_UNKNOWN || level >= n_entries)
>> -		level = default_entry;
>> -
>>  	if (WARN_ON_ONCE(n_entries == 0))
>>  		return 0;
>> -	if (WARN_ON_ONCE(level >= n_entries))
>> -		level = n_entries - 1;
>> +
>> +	if (WARN_ON_ONCE(default_entry >= n_entries))
>> +		default_entry = n_entries - 1;
>> +
>> +	if (port_info->hdmi_level_shift_set &&
>> +	    !WARN_ON_ONCE(port_info->hdmi_level_shift >= n_entries)) {
>> +		level = port_info->hdmi_level_shift;
>> +	} else {
>> +		level = default_entry;
>> +	}
>
> I'd probably simplify that to something like:
>
> if (level_shift_set)
> 	level = level_shift;
> else
> 	level = default;
> if (WARN_ON_ONCE(level >= n_entries))
> 	level = n_entries - 1;

I wanted to add the distinction between the default_entry being bogus
and the VBT being bogus.

BR,
Jani.

>
> Either way:
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
>>  
>>  	return level;
>>  }
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 7e0f67babe20..67bdfe6de3fa 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -627,13 +627,9 @@ struct ddi_vbt_port_info {
>>  
>>  	int max_tmds_clock;
>>  
>> -	/*
>> -	 * This is an index in the HDMI/DVI DDI buffer translation table.
>> -	 * The special value HDMI_LEVEL_SHIFT_UNKNOWN means the VBT didn't
>> -	 * populate this field.
>> -	 */
>> -#define HDMI_LEVEL_SHIFT_UNKNOWN	0xff
>> +	/* This is an index in the HDMI/DVI DDI buffer translation table. */
>>  	u8 hdmi_level_shift;
>> +	u8 hdmi_level_shift_set:1;
>>  
>>  	u8 supports_dvi:1;
>>  	u8 supports_hdmi:1;
>> -- 
>> 2.20.1

-- 
Jani Nikula, Intel Open Source Graphics Center
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