Re: [PATCH 3/3] drm/i915: Get panel_type from OpRegion panel details

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

On Fri, 08 Apr 2016, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We've had problems on several occasions with using the panel type
> from the VBT block 40. Usually it seems to be 2, which often
> doesn't give us the correct timings for the panel. After some
> more digging I found a way to get a panel type via the OpRegion
> SWSCI GBDA "Get Panel Details" method. Let's try to use it.
>
> The spec has this to say about the output:
> "Bits [15:8] - Panel Type
>  Bits contain the panel type user setting from CMOS
>  00h = Not Valid, use default Panel Type & Timings from VBT
>  01h - 0Fh = Panel Number"
>
> The other bits in the output don't look relevant for the problem at
> hand.
>
> The input is specified as:
> "Bits [31:4] - Reserved
>  Reserved (must be zero)
>  Bits [3:0] - Panel Number
>  These bits contain the sequential index of Panel, starting at 0 and
>  counting upwards from the first integrated Internal Flat-Panel Display
>  Encoder present, and then from the first external Display Encoder
>  (e.g., S/DVO-B then S/DVO-C) which supports Internal Flat-Panels.
>  0h - 0Fh = Panel number"
>
> For now I've just hardcoded the input panel number as 0. That would seem
> like a decent choise for LVDS. Not so sure about eDP when port != A.

Frankly, I didn't understand the point of the input parameter for
figuring out the output. The spec is written for someone who already
knows what they're doing...

>
> Cc: Rob Kramer <rob@solution-space.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94825
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h       |  5 +++++
>  drivers/gpu/drm/i915/intel_bios.c     | 13 ++++++++++---
>  drivers/gpu/drm/i915/intel_opregion.c | 13 +++++++++++++
>  3 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 53ace572b292..533263a7a12d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3421,6 +3421,7 @@ extern int intel_opregion_notify_encoder(struct intel_encoder *intel_encoder,
>  					 bool enable);
>  extern int intel_opregion_notify_adapter(struct drm_device *dev,
>  					 pci_power_t state);
> +extern int intel_opregion_get_panel_type(struct drm_device *dev);
>  #else
>  static inline int intel_opregion_setup(struct drm_device *dev) { return 0; }
>  static inline void intel_opregion_init(struct drm_device *dev) { return; }
> @@ -3436,6 +3437,10 @@ intel_opregion_notify_adapter(struct drm_device *dev, pci_power_t state)
>  {
>  	return 0;
>  }
> +static inline int intel_opregion_get_panel_type(struct drm_device *dev)
> +{
> +	return 0;
> +}
>  #endif
>  
>  /* intel_acpi.c */
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index d9568be4b33b..718e49931b5f 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -205,16 +205,23 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
>  	struct drm_display_mode *panel_fixed_mode;
>  	int panel_type;
>  	int drrs_mode;
> +	int ret;
>  
>  	lvds_options = find_section(bdb, BDB_LVDS_OPTIONS);
>  	if (!lvds_options)
>  		return;
>  
>  	dev_priv->vbt.lvds_dither = lvds_options->pixel_dither;
> -	if (lvds_options->panel_type > 0xf)
> -		return;
>  
> -	panel_type = lvds_options->panel_type;
> +	ret = intel_opregion_get_panel_type(dev_priv->dev);
> +	if (ret >= 0x1 && ret <= 0xf) {

Undecided whether I'd like to have this check within
intel_opregion_get_panel_type(). Just make that return 0 for "use vbt"
(and CONFIG_ACPI=n), and valid stuff otherwise? *shrug*

> +		panel_type = ret;
> +	} else {
> +		if (lvds_options->panel_type > 0xf)
> +			return;
> +		panel_type = lvds_options->panel_type;
> +	}
> +

If this actually works, I'd like to have some debug logging for pretty
much all the code paths here.

Other than that, seems fine.

BR,
Jani.

>  	dev_priv->vbt.panel_type = panel_type;
>  
>  	drrs_mode = (lvds_options->dps_panel_type_bits
> diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
> index c15718b4862a..5e17fa5dc869 100644
> --- a/drivers/gpu/drm/i915/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/intel_opregion.c
> @@ -1024,3 +1024,16 @@ err_out:
>  	memunmap(base);
>  	return err;
>  }
> +
> +int
> +intel_opregion_get_panel_type(struct drm_device *dev)
> +{
> +	u32 panel_details;
> +	int ret;
> +
> +	ret = swsci(dev, SWSCI_GBDA_PANEL_DETAILS, 0x0, &panel_details);
> +	if (ret)
> +		return ret;
> +
> +	return (panel_details >> 8) & 0xff;
> +}

-- 
Jani Nikula, Intel Open Source Technology Center
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