Great!
Although I'd prefer at intel_drrs.c.. ;)
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
On Fri, Jan 9, 2015 at 12:56 PM, Vandana Kannan
<vandana.kannan@xxxxxxxxx> wrote:
> Adding an overview of DRRS in general and the implementation for eDP DRRS.
> Also, describing the functions related to eDP DRRS.
>
> Signed-off-by: Vandana Kannan <vandana.kannan@xxxxxxxxx>
> ---
> Documentation/DocBook/drm.tmpl | 11 +++++
> drivers/gpu/drm/i915/intel_dp.c | 95 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 106 insertions(+)
>
> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
> index 3b2571e..8c844b4 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -4042,6 +4042,17 @@ int num_ioctls;</synopsis>
> !Idrivers/gpu/drm/i915/intel_fbc.c
> </sect2>
> <sect2>
> + <title>Display Refresh Rate Switching (DRRS)</title>
> +!Pdrivers/gpu/drm/i915/intel_dp.c Display Refresh Rate Switching (DRRS)
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_set_drrs_state
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_enable
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_disable
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_invalidate
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_edp_drrs_flush
> +!Fdrivers/gpu/drm/i915/intel_dp.c intel_dp_drrs_init
> +
> + </sect2>
> + <sect2>
> <title>DPIO</title>
> !Pdrivers/gpu/drm/i915/i915_reg.h DPIO
> <table id="dpiox2">
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 42195fe..eda90d6 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4745,6 +4745,18 @@ intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
> I915_READ(pp_div_reg));
> }
>
> +/**
> + * intel_dp_set_drrs_state - program registers for RR switch to take effect
> + * @dev: DRM device
> + * @refresh_rate: RR to be programmed
> + *
> + * This function gets called when refresh rate (RR) has to be changed from
> + * one frequency to another. Switches can be between high and low RR
> + * supported by the panel or to any other RR based on media playback (in
> + * this case, RR value needs to be passed from user space).
> + *
> + * The caller of this function needs to take a lock on dev_priv->drrs.
> + */
> static void intel_dp_set_drrs_state(struct drm_device *dev, int refresh_rate)
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -4838,6 +4850,12 @@ static void intel_dp_set_drrs_state(struct drm_device *dev, int refresh_rate)
> DRM_DEBUG_KMS("eDP Refresh Rate set to : %dHz\n", refresh_rate);
> }
>
> +/**
> + * intel_edp_drrs_enable - init drrs struct if supported
> + * @intel_dp: DP struct
> + *
> + * Initializes frontbuffer_bits and drrs.dp
> + */
> void intel_edp_drrs_enable(struct intel_dp *intel_dp)
> {
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> @@ -4864,6 +4882,11 @@ void intel_edp_drrs_enable(struct intel_dp *intel_dp)
> mutex_unlock(&dev_priv->drrs.mutex);
> }
>
> +/**
> + * intel_edp_drrs_disable - Disable DRRS
> + * @intel_dp: DP struct
> + *
> + */
> void intel_edp_drrs_disable(struct intel_dp *intel_dp)
> {
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> @@ -4921,6 +4944,17 @@ unlock:
> mutex_unlock(&dev_priv->drrs.mutex);
> }
>
> +/**
> + * intel_edp_drrs_invalidate - Invalidate DRRS
> + * @dev: DRM device
> + * @frontbuffer_bits: frontbuffer plane tracking bits
> + *
> + * When there is a disturbance on screen (due to cursor movement/time
> + * update etc), DRRS needs to be invalidated, i.e. need to switch to
> + * high RR.
> + *
> + * Dirty frontbuffers relevant to DRRS are tracked in busy_frontbuffer_bits.
> + */
> void intel_edp_drrs_invalidate(struct drm_device *dev,
> unsigned frontbuffer_bits)
> {
> @@ -4948,6 +4982,17 @@ void intel_edp_drrs_invalidate(struct drm_device *dev,
> mutex_unlock(&dev_priv->drrs.mutex);
> }
>
> +/**
> + * intel_edp_drrs_flush - Flush DRRS
> + * @dev: DRM device
> + * @frontbuffer_bits: frontbuffer plane tracking bits
> + *
> + * When there is no movement on screen, DRRS work can be scheduled.
> + * This DRRS work is responsible for setting relevant registers after a
> + * timeout of 1 second.
> + *
> + * Dirty frontbuffers relevant to DRRS are tracked in busy_frontbuffer_bits.
> + */
> void intel_edp_drrs_flush(struct drm_device *dev,
> unsigned frontbuffer_bits)
> {
> @@ -4972,6 +5017,56 @@ void intel_edp_drrs_flush(struct drm_device *dev,
> mutex_unlock(&dev_priv->drrs.mutex);
> }
>
> +/**
> + * DOC: Display Refresh Rate Switching (DRRS)
> + *
> + * Display Refresh Rate Switching (DRRS) is a power conservation feature
> + * which enables swtching between low and high refresh rates,
> + * dynamically, based on the usage scenario. This feature is applicable
> + * for internal panels.
> + *
> + * Indication that the panel supports DRRS is given by the panel EDID, which
> + * would list multiple refresh rates for one resolution.
> + *
> + * DRRS is of 2 types - static and seamless.
> + * Static DRRS involves changing refresh rate (RR) by doing a full modeset
> + * (may appear as a blink on screen) and is used in dock-undock scenario.
> + * Seamless DRRS involves changing RR without any visual effect to the user
> + * and can be used during normal system usage. This is done by programming
> + * certain registers.
> + *
> + * Support for static/seamless DRRS may be indicated in the VBT based on
> + * inputs from the panel spec.
> + *
> + * DRRS saves power by switching to low RR based on usage scenarios.
> + *
> + * eDP DRRS:-
> + * The implementation is based on frontbuffer tracking implementation.
> + * When there is a disturbance on the screen triggered by user activity or a
> + * periodic system activity, DRRS is disabled (RR is changed to high RR).
> + * When there is no movement on screen, after a timeout of 1 second, a switch
> + * to low RR is made.
> + * For integration with frontbuffer tracking code,
> + * intel_edp_drrs_invalidate() and intel_edp_drrs_flush() are called.
> + *
> + * DRRS can be further extended to support other internal panels and also
> + * the scenario of video playback wherein RR is set based on the rate
> + * requested by userspace.
> + */
> +
> +/**
> + * intel_dp_drrs_init - Init basic DRRS work and mutex.
> + * @intel_connector: eDP connector
> + * @fixed_mode: preferred mode of panel
> + *
> + * This function is called only once at driver load to initialize basic
> + * DRRS stuff.
> + *
> + * Returns:
> + * Downclock mode if panel supports it, else return NULL.
> + * DRRS support is determined by the presence of downclock mode (apart
> + * from VBT setting).
> + */
> static struct drm_display_mode *
> intel_dp_drrs_init(struct intel_connector *intel_connector,
> struct drm_display_mode *fixed_mode)
> --
> 2.0.1
>
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--
Rodrigo Vivi
Blog: http://blog.vivi.eng.br
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