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

[Vandana Kannan <vandana.kannan@intel.com>]

On Jan-22-2014 6:39 PM, Jani Nikula wrote:
> On Mon, 23 Dec 2013, 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.
>>
>> 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   |    9 +++++++++
>>  drivers/gpu/drm/i915/intel_bios.c |   23 +++++++++++++++++++++++
>>  drivers/gpu/drm/i915/intel_bios.h |   29 +++++++++++++++++++++++++++++
>>  3 files changed, 61 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index ae2c80c..f8fd045 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -1174,6 +1174,15 @@ struct intel_vbt_data {
>>  	int lvds_ssc_freq;
>>  	unsigned int bios_lvds_val; /* initial [PCH_]LVDS reg val in VBIOS */
>>  
>> +	/**
> 
> This is not a kerneldoc comment, so drop the extra *.
> 
Ok.
>> +	 * DRRS mode type (Seamless OR Static DRRS)
>> +	 * drrs_mode Val 0x2 is Seamless DRRS and 0 is Static DRRS.
>> +	 * These values correspond to the VBT values for drrs mode.
>> +	 */
>> +	int drrs_mode;
>> +	/* DRRS enabled or disabled in VBT */
>> +	bool drrs_enabled;
> 
> Both the drrs_mode and drrs_enabled should be replaced by one enum
> drrs_support_type which you introduce later. It's all self-explanatory
> that way, and you don't need to explain so much.
> 
There are 2 options in the VBT. drrs_enabled to check if DRRS is
supported, drrs_mode to show which type. It has been added here as it is
for readability.
>> +
>>  	/* 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 f88e507..5b04a69 100644
>> --- a/drivers/gpu/drm/i915/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/intel_bios.c
>> @@ -195,6 +195,21 @@ get_lvds_fp_timing(const struct bdb_header *bdb,
>>  	return (const struct lvds_fp_timing *)((const u8 *)bdb + ofs);
>>  }
>>  
>> +/**
>> + * This function returns the 2 bit information pertaining to a panel type
>> + * present in a 32 bit field in VBT blocks. There are 16 panel types in VBT
>> + * each occupying 2 bits of information in some 32 bit fields of VBT blocks.
>> + */
>> +static int
>> +get_mode_by_paneltype(unsigned int word)
>> +{
>> +	/**
>> +	 * The caller of this API should interpret the 2 bits
>> +	 * based on VBT description for that field.
>> +	 */
>> +	return (word >> ((panel_type - 1) * 2)) & MODE_MASK;
> 
> Everywhere else in intel_bios.c panel_type is used 0-based.
> 
VBT indexes panel type as 1,2,3. Therefore, we have to make the change
to match kernel's 0-based usage.
>> +}
> 
> You use the above function only once. IMHO with all the explaining above
> it's just too much of a burden to the reader. Just do this in the code.
> 
Ok.
>> +
>>  /* Try to find integrated panel data */
>>  static void
>>  parse_lfp_panel_data(struct drm_i915_private *dev_priv,
>> @@ -218,6 +233,11 @@ parse_lfp_panel_data(struct drm_i915_private *dev_priv,
>>  
>>  	panel_type = lvds_options->panel_type;
>>  
>> +	dev_priv->vbt.drrs_mode =
>> +		get_mode_by_paneltype(lvds_options->dps_panel_type_bits);
>> +	DRM_DEBUG_KMS("DRRS supported mode is : %s\n",
>                                              ^ drop the space here
> 
Ok
>> +			(dev_priv->vbt.drrs_mode == 0) ? "STATIC" : "SEAMLESS");
> 
> Why shouting?
> 
>> +
>>  	lvds_lfp_data = find_section(bdb, BDB_LVDS_LFP_DATA);
>>  	if (!lvds_lfp_data)
>>  		return;
>> @@ -488,6 +508,9 @@ parse_driver_features(struct drm_i915_private *dev_priv,
>>  
>>  	if (driver->dual_frequency)
>>  		dev_priv->render_reclock_avail = true;
>> +
>> +	dev_priv->vbt.drrs_enabled = driver->drrs_state;
>> +	DRM_DEBUG_KMS("DRRS State Enabled : %d\n", driver->drrs_state);
>                                          ^ and here and everywhere
> 
Ok
>>  }
>>  
>>  static void
>> diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
>> index 81ed58c..0a3a751 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;
> 
> Why does this have "lvds" but the rest not? Why do some fields end in
> "bits" but some others not? Some consistency please.
> 
This is how the vbt block definition doc mentions each of these fields.
This is the reason why it has been added in this manner.

>> +	/* 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;
> 
> I really *really* wish I knew why some stuff is specified in the lvds
> bios blob and some other in edp blob and some stuff specified here is
> used in the edp side. Ugh. I wonder if we should check this
> panel_color_depth for edp too.
>
This is how the vbt block definition doc mentions each of these fields.
This is the reason why it has been added in this manner.

>> +	/* 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 */
>> @@ -462,6 +477,20 @@ struct bdb_driver_features {
>>  
>>  	u8 hdmi_termination;
>>  	u8 custom_vbt_version;
>> +	/* Driver features data block */
>> +	u16 rmpm_state:1;
>> +	u16 s2ddt_state:1;
>> +	u16 dpst_state:1;
>> +	u16 bltclt_state:1;
>> +	u16 adb_state:1;
>> +	u16 drrs_state:1;
>> +	u16 grs_state:1;
>> +	u16 gpmt_state:1;
>> +	u16 tbt_state:1;
>> +	u16 psr_state:1;
>> +	u16 ips_state:1;
> 
> All of the above should be foo_enabled to make them self-explanatory.
> 
>> +	u16 reserved3:4;
>> +	u16 pc_feature_validity:1;
> 
> Similarly for this one, should be pc_feature_valid.
> 
This is how the vbt block definition doc mentions this field.
This is the reason why it has been added in this manner.
>>  } __packed;
>>  
>>  #define EDP_18BPP	0
>> -- 
>> 1.7.9.5
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>