Re: [PATCH 1/5] drm/i915: Adding VBT fields to support eDP DRRS feature

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Fri, 14 Feb 2014 15:32:18 +0530
Vandana Kannan <vandana.kannan@intel.com> wrote:

> From: Pradeep Bhat <pradeep.bhat@intel.com>
> 
> This patch reads the DRRS support and Mode type from VBT fields.
> The read information will be stored in VBT struct during BIOS
> parsing. The above functionality is needed for decision making
> whether DRRS feature is supported in i915 driver for eDP panels.
> This information helps us decide if seamless DRRS can be done
> at runtime to support certain power saving features. This patch
> was tested by setting necessary bit in VBT struct and merging
> the new VBT with system BIOS so that we can read the value.
> 
> v2: Incorporated review comments from Chris Wilson
> Removed "intel_" as a prefix for DRRS specific declarations.
> 
> v3: Incorporated Jani's review comments
> Removed function which deducts drrs mode from panel_type. Modified some
> print statements. Made changes to use DRRS_NOT_SUPPORTED as 0 instead of -1.
> 
> Signed-off-by: Pradeep Bhat <pradeep.bhat@intel.com>
> Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h   |   13 +++++++++++++
>  drivers/gpu/drm/i915/intel_bios.c |   29 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_bios.h |   29 +++++++++++++++++++++++++++++
>  3 files changed, 71 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 728b9c3..6b4d0b20 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1218,6 +1218,12 @@ struct ddi_vbt_port_info {
>  	uint8_t supports_dp:1;
>  };
>  
> +enum drrs_support_type {
> +	DRRS_NOT_SUPPORTED = 0,
> +	STATIC_DRRS_SUPPORT = 1,
> +	SEAMLESS_DRRS_SUPPORT = 2
> +};
> +
>  struct intel_vbt_data {
>  	struct drm_display_mode *lfp_lvds_vbt_mode; /* if any */
>  	struct drm_display_mode *sdvo_lvds_vbt_mode; /* if any */
> @@ -1233,6 +1239,13 @@ struct intel_vbt_data {
>  	int lvds_ssc_freq;
>  	unsigned int bios_lvds_val; /* initial [PCH_]LVDS reg val in VBIOS */
>  
> +	/*
> +	 * DRRS support type (Seamless OR Static DRRS OR not supported)
> +	 * drrs_support type Val 0x2 is Seamless DRRS and 0 is Static DRRS.
> +	 * These values correspond to the VBT values for drrs mode.
> +	 */
> +	enum drrs_support_type drrs_type;
> +
>  	/* eDP */
>  	int edp_rate;
>  	int edp_lanes;
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index 86b95ca..2414eca 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -218,6 +218,25 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
>  
>  	panel_type = lvds_options->panel_type;
>  
> +	dev_priv->vbt.drrs_type = (lvds_options->dps_panel_type_bits
> +					>> (panel_type * 2)) & MODE_MASK;
> +	/*
> +	 * VBT has static DRRS = 0 and seamless DRRS = 2.
> +	 * The below piece of code is required to adjust vbt.drrs_type
> +	 * to match the enum drrs_support_type.
> +	 */
> +	switch (dev_priv->vbt.drrs_type) {
> +	case 0:
> +		dev_priv->vbt.drrs_type = STATIC_DRRS_SUPPORT;
> +		DRM_DEBUG_KMS("DRRS supported mode is static\n");
> +		break;
> +	case 2:
> +		DRM_DEBUG_KMS("DRRS supported mode is seamless\n");
> +		break;
> +	default:
> +		break;
> +	}
> +
>  	lvds_lfp_data = find_section(bdb, BDB_LVDS_LFP_DATA);
>  	if (!lvds_lfp_data)
>  		return;
> @@ -516,6 +535,16 @@ parse_driver_features(struct drm_i915_private *dev_priv,
>  
>  	if (driver->dual_frequency)
>  		dev_priv->render_reclock_avail = true;
> +
> +	DRM_DEBUG_KMS("DRRS State Enabled:%d\n", driver->drrs_enabled);
> +	/*
> +	 * If DRRS is not supported, drrs_type has to be set to 0.
> +	 * This is because, VBT is configured in such a way that
> +	 * static DRRS is 0 and DRRS not supported is represented by
> +	 * driver->drrs_enabled=false
> +	 */
> +	if (!driver->drrs_enabled)
> +		dev_priv->vbt.drrs_type = driver->drrs_enabled;
>  }
>  
>  static void
> diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
> index 282de5e..5505d6c 100644
> --- a/drivers/gpu/drm/i915/intel_bios.h
> +++ b/drivers/gpu/drm/i915/intel_bios.h
> @@ -281,6 +281,9 @@ struct bdb_general_definitions {
>  	union child_device_config devices[0];
>  } __packed;
>  
> +/* Mask for DRRS / Panel Channel / SSC / BLT control bits extraction */
> +#define MODE_MASK		0x3
> +
>  struct bdb_lvds_options {
>  	u8 panel_type;
>  	u8 rsvd1;
> @@ -293,6 +296,18 @@ struct bdb_lvds_options {
>  	u8 lvds_edid:1;
>  	u8 rsvd2:1;
>  	u8 rsvd4;
> +	/* LVDS Panel channel bits stored here */
> +	u32 lvds_panel_channel_bits;
> +	/* LVDS SSC (Spread Spectrum Clock) bits stored here. */
> +	u16 ssc_bits;
> +	u16 ssc_freq;
> +	u16 ssc_ddt;
> +	/* Panel color depth defined here */
> +	u16 panel_color_depth;
> +	/* LVDS panel type bits stored here */
> +	u32 dps_panel_type_bits;
> +	/* LVDS backlight control type bits stored here */
> +	u32 blt_control_type_bits;
>  } __packed;
>  
>  /* LFP pointer table contains entries to the struct below */
> @@ -478,6 +493,20 @@ struct bdb_driver_features {
>  
>  	u8 hdmi_termination;
>  	u8 custom_vbt_version;
> +	/* Driver features data block */
> +	u16 rmpm_enabled:1;
> +	u16 s2ddt_enabled:1;
> +	u16 dpst_enabled:1;
> +	u16 bltclt_enabled:1;
> +	u16 adb_enabled:1;
> +	u16 drrs_enabled:1;
> +	u16 grs_enabled:1;
> +	u16 gpmt_enabled:1;
> +	u16 tbt_enabled:1;
> +	u16 psr_enabled:1;
> +	u16 ips_enabled:1;
> +	u16 reserved3:4;
> +	u16 pc_feature_valid:1;
>  } __packed;
>  
>  #define EDP_18BPP	0

Since I can't trust the VBT doc I have, I assume this has been tested
on real machines and works.

So:
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>

The VBT choosing 0 for static and 2 for seamless is a bit annoying, but
I guess there's not much we can do about that now...

-- 
Jesse Barnes, Intel Open Source Technology Center