Re: [PATCH v3 4/9] drm/i915: Keep track of pwm-related backlight hooks separately

[Jani Nikula]

On Fri, 04 Dec 2020, Lyude Paul <lyude@xxxxxxxxxx> wrote:
> Currently, every different type of backlight hook that i915 supports is
> pretty straight forward - you have a backlight, probably through PWM
> (but maybe DPCD), with a single set of platform-specific hooks that are
> used for controlling it.
>
> HDR backlights, in particular VESA and Intel's HDR backlight
> implementations, can end up being more complicated. With Intel's
> proprietary interface, HDR backlight controls always run through the
> DPCD. When the backlight is in SDR backlight mode however, the driver
> may need to bypass the TCON and control the backlight directly through
> PWM.
>
> So, in order to support this we'll need to split our backlight callbacks
> into two groups: a set of high-level backlight control callbacks in
> intel_panel, and an additional set of pwm-specific backlight control
> callbacks. This also implies a functional changes for how these
> callbacks are used:
>
> * We now keep track of two separate backlight level ranges, one for the
>   high-level backlight, and one for the pwm backlight range
> * We also keep track of backlight enablement and PWM backlight
>   enablement separately
> * Since the currently set backlight level might not be the same as the
>   currently programmed PWM backlight level, we stop setting
>   panel->backlight.level with the currently programmed PWM backlight
>   level in panel->backlight.pwm_funcs->setup(). Instead, we rely
>   on the higher level backlight control functions to retrieve the
>   current PWM backlight level (in this case, intel_pwm_get_backlight()).
>   Note that there are still a few PWM backlight setup callbacks that
>   do actually need to retrieve the current PWM backlight level, although
>   we no longer save this value in panel->backlight.level like before.
>
> Additionally, we drop the call to lpt_get_backlight() in
> lpt_setup_backlight(), and avoid unconditionally writing the PWM value that
> we get from it and only write it back if we're in PCH mode. The reason for

Should be something like, "...only write it back if we're in CPU mode,
and switching to PCH mode."

> this is because in the original codepath for this, it was expected that the
> intel_panel_bl_funcs->setup() hook would be responsible for fetching the
> initial backlight level. On lpt systems, the only time we could ever be in
> PCH backlight mode is during the initial driver load - meaning that outside
> of the setup() hook, lpt_get_backlight() will always be the callback used
> for retrieving the current backlight level. After this patch we still need
> to fetch and write-back the PCH backlight value if we're in PCH mode, but

Ditto here. We may probe at CPU mode, set up by BIOS/GOP, but we always
switch to PCH override mode. (The pch_ prefixed function naming is
misleading...)

Historically there was a CPU register for pwm control. Then the
functionality was moved to PCH but the register remained. Then there was
a transition to PCH register, but the CPU register remained and used
some low level internal messaging from CPU to PCH, unless PCH override
was set. Finally the messaging was removed. Anyway, on the CPU+PCH
combos where we can choose, we prefer using the PCH register directly
("PCH mode") and not use the CPU register with messaging. Simple made
complex(tm).

> because intel_pwm_setup_backlight() will retrieve the backlight level after
> setup() using the get() hook, which always ends up being
> lpt_get_backlight(). Thus - an additional call to lpt_get_backlight() in
> lpt_setup_backlight() is made redundant.
>
> v3:
> * Reuse intel_panel_bl_funcs() for pwm_funcs
> * Explain why we drop lpt_get_backlight()
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> Cc: thaytan@xxxxxxxxxxxx
> Cc: Vasily Khoruzhick <anarsoul@xxxxxxxxx>
> ---
>  .../drm/i915/display/intel_display_types.h    |   4 +
>  drivers/gpu/drm/i915/display/intel_panel.c    | 344 ++++++++++--------
>  2 files changed, 194 insertions(+), 154 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index a70d1bf29aa5..47ee565c49a2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -252,6 +252,9 @@ struct intel_panel {
>  		bool alternate_pwm_increment;	/* lpt+ */
>  
>  		/* PWM chip */
> +		u32 pwm_min;
> +		u32 pwm_max;
> +		bool pwm_enabled;
>  		bool util_pin_active_low;	/* bxt+ */
>  		u8 controller;		/* bxt+ only */
>  		struct pwm_device *pwm;
> @@ -263,6 +266,7 @@ struct intel_panel {
>  		struct backlight_device *device;
>  
>  		const struct intel_panel_bl_funcs *funcs;
> +		const struct intel_panel_bl_funcs *pwm_funcs;
>  		void (*power)(struct intel_connector *, bool enable);
>  	} backlight;
>  };
> diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
> index 67f81ae995c4..41f0d2b2c627 100644
> --- a/drivers/gpu/drm/i915/display/intel_panel.c
> +++ b/drivers/gpu/drm/i915/display/intel_panel.c
> @@ -511,25 +511,34 @@ static u32 scale_hw_to_user(struct intel_connector *connector,
>  		     0, user_max);
>  }
>  
> -static u32 intel_panel_compute_brightness(struct intel_connector *connector,
> -					  u32 val)
> +static u32 intel_panel_sanitize_pwm_level(struct intel_connector *connector, u32 val)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
>  
> -	drm_WARN_ON(&dev_priv->drm, panel->backlight.max == 0);
> +	drm_WARN_ON(&dev_priv->drm, panel->backlight.pwm_max == 0);
>  
>  	if (dev_priv->params.invert_brightness < 0)
>  		return val;
>  
>  	if (dev_priv->params.invert_brightness > 0 ||
>  	    dev_priv->quirks & QUIRK_INVERT_BRIGHTNESS) {
> -		return panel->backlight.max - val + panel->backlight.min;
> +		return panel->backlight.pwm_max - val + panel->backlight.pwm_min;
>  	}
>  
>  	return val;
>  }
>  
> +static void intel_panel_set_pwm_level(const struct drm_connector_state *conn_state, u32 val)
> +{
> +	struct intel_connector *connector = to_intel_connector(conn_state->connector);
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct intel_panel *panel = &connector->panel;
> +
> +	drm_dbg_kms(&i915->drm, "set backlight PWM = %d\n", val);
> +	panel->backlight.pwm_funcs->set(conn_state, val);
> +}
> +
>  static u32 lpt_get_backlight(struct intel_connector *connector)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> @@ -624,12 +633,12 @@ static void i9xx_set_backlight(const struct drm_connector_state *conn_state, u32
>  	struct intel_panel *panel = &connector->panel;
>  	u32 tmp, mask;
>  
> -	drm_WARN_ON(&dev_priv->drm, panel->backlight.max == 0);
> +	drm_WARN_ON(&dev_priv->drm, panel->backlight.pwm_max == 0);
>  
>  	if (panel->backlight.combination_mode) {
>  		u8 lbpc;
>  
> -		lbpc = level * 0xfe / panel->backlight.max + 1;
> +		lbpc = level * 0xfe / panel->backlight.pwm_max + 1;
>  		level /= lbpc;
>  		pci_write_config_byte(dev_priv->drm.pdev, LBPC, lbpc);
>  	}
> @@ -681,9 +690,8 @@ intel_panel_actually_set_backlight(const struct drm_connector_state *conn_state,
>  	struct drm_i915_private *i915 = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
>  
> -	drm_dbg_kms(&i915->drm, "set backlight PWM = %d\n", level);
> +	drm_dbg_kms(&i915->drm, "set backlight level = %d\n", level);
>  
> -	level = intel_panel_compute_brightness(connector, level);
>  	panel->backlight.funcs->set(conn_state, level);
>  }
>  
> @@ -732,7 +740,7 @@ static void lpt_disable_backlight(const struct drm_connector_state *old_conn_sta
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, level);
> +	intel_panel_set_pwm_level(old_conn_state, level);
>  
>  	/*
>  	 * Although we don't support or enable CPU PWM with LPT/SPT based
> @@ -760,7 +768,7 @@ static void pch_disable_backlight(const struct drm_connector_state *old_conn_sta
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  
>  	tmp = intel_de_read(dev_priv, BLC_PWM_CPU_CTL2);
>  	intel_de_write(dev_priv, BLC_PWM_CPU_CTL2, tmp & ~BLM_PWM_ENABLE);
> @@ -771,7 +779,7 @@ static void pch_disable_backlight(const struct drm_connector_state *old_conn_sta
>  
>  static void i9xx_disable_backlight(const struct drm_connector_state *old_conn_state, u32 val)
>  {
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  }
>  
>  static void i965_disable_backlight(const struct drm_connector_state *old_conn_state, u32 val)
> @@ -779,7 +787,7 @@ static void i965_disable_backlight(const struct drm_connector_state *old_conn_st
>  	struct drm_i915_private *dev_priv = to_i915(old_conn_state->connector->dev);
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  
>  	tmp = intel_de_read(dev_priv, BLC_PWM_CTL2);
>  	intel_de_write(dev_priv, BLC_PWM_CTL2, tmp & ~BLM_PWM_ENABLE);
> @@ -792,7 +800,7 @@ static void vlv_disable_backlight(const struct drm_connector_state *old_conn_sta
>  	enum pipe pipe = to_intel_crtc(old_conn_state->crtc)->pipe;
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  
>  	tmp = intel_de_read(dev_priv, VLV_BLC_PWM_CTL2(pipe));
>  	intel_de_write(dev_priv, VLV_BLC_PWM_CTL2(pipe),
> @@ -806,7 +814,7 @@ static void bxt_disable_backlight(const struct drm_connector_state *old_conn_sta
>  	struct intel_panel *panel = &connector->panel;
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  
>  	tmp = intel_de_read(dev_priv,
>  			    BXT_BLC_PWM_CTL(panel->backlight.controller));
> @@ -827,7 +835,7 @@ static void cnp_disable_backlight(const struct drm_connector_state *old_conn_sta
>  	struct intel_panel *panel = &connector->panel;
>  	u32 tmp;
>  
> -	intel_panel_actually_set_backlight(old_conn_state, val);
> +	intel_panel_set_pwm_level(old_conn_state, val);
>  
>  	tmp = intel_de_read(dev_priv,
>  			    BXT_BLC_PWM_CTL(panel->backlight.controller));
> @@ -906,7 +914,7 @@ static void lpt_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		intel_de_write(dev_priv, SOUTH_CHICKEN1, schicken);
>  	}
>  
> -	pch_ctl2 = panel->backlight.max << 16;
> +	pch_ctl2 = panel->backlight.pwm_max << 16;
>  	intel_de_write(dev_priv, BLC_PWM_PCH_CTL2, pch_ctl2);
>  
>  	pch_ctl1 = 0;
> @@ -923,7 +931,7 @@ static void lpt_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		       pch_ctl1 | BLM_PCH_PWM_ENABLE);
>  
>  	/* This won't stick until the above enable. */
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  }
>  
>  static void pch_enable_backlight(const struct intel_crtc_state *crtc_state,
> @@ -958,9 +966,9 @@ static void pch_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	intel_de_write(dev_priv, BLC_PWM_CPU_CTL2, cpu_ctl2 | BLM_PWM_ENABLE);
>  
>  	/* This won't stick until the above enable. */
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  
> -	pch_ctl2 = panel->backlight.max << 16;
> +	pch_ctl2 = panel->backlight.pwm_max << 16;
>  	intel_de_write(dev_priv, BLC_PWM_PCH_CTL2, pch_ctl2);
>  
>  	pch_ctl1 = 0;
> @@ -987,7 +995,7 @@ static void i9xx_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		intel_de_write(dev_priv, BLC_PWM_CTL, 0);
>  	}
>  
> -	freq = panel->backlight.max;
> +	freq = panel->backlight.pwm_max;
>  	if (panel->backlight.combination_mode)
>  		freq /= 0xff;
>  
> @@ -1001,7 +1009,7 @@ static void i9xx_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	intel_de_posting_read(dev_priv, BLC_PWM_CTL);
>  
>  	/* XXX: combine this into above write? */
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  
>  	/*
>  	 * Needed to enable backlight on some 855gm models. BLC_HIST_CTL is
> @@ -1028,7 +1036,7 @@ static void i965_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		intel_de_write(dev_priv, BLC_PWM_CTL2, ctl2);
>  	}
>  
> -	freq = panel->backlight.max;
> +	freq = panel->backlight.pwm_max;
>  	if (panel->backlight.combination_mode)
>  		freq /= 0xff;
>  
> @@ -1044,7 +1052,7 @@ static void i965_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	intel_de_posting_read(dev_priv, BLC_PWM_CTL2);
>  	intel_de_write(dev_priv, BLC_PWM_CTL2, ctl2 | BLM_PWM_ENABLE);
>  
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  }
>  
>  static void vlv_enable_backlight(const struct intel_crtc_state *crtc_state,
> @@ -1063,11 +1071,11 @@ static void vlv_enable_backlight(const struct intel_crtc_state *crtc_state,
>  		intel_de_write(dev_priv, VLV_BLC_PWM_CTL2(pipe), ctl2);
>  	}
>  
> -	ctl = panel->backlight.max << 16;
> +	ctl = panel->backlight.pwm_max << 16;
>  	intel_de_write(dev_priv, VLV_BLC_PWM_CTL(pipe), ctl);
>  
>  	/* XXX: combine this into above write? */
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  
>  	ctl2 = 0;
>  	if (panel->backlight.active_low_pwm)
> @@ -1116,9 +1124,9 @@ static void bxt_enable_backlight(const struct intel_crtc_state *crtc_state,
>  
>  	intel_de_write(dev_priv,
>  		       BXT_BLC_PWM_FREQ(panel->backlight.controller),
> -		       panel->backlight.max);
> +		       panel->backlight.pwm_max);
>  
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  
>  	pwm_ctl = 0;
>  	if (panel->backlight.active_low_pwm)
> @@ -1152,9 +1160,9 @@ static void cnp_enable_backlight(const struct intel_crtc_state *crtc_state,
>  
>  	intel_de_write(dev_priv,
>  		       BXT_BLC_PWM_FREQ(panel->backlight.controller),
> -		       panel->backlight.max);
> +		       panel->backlight.pwm_max);
>  
> -	intel_panel_actually_set_backlight(conn_state, level);
> +	intel_panel_set_pwm_level(conn_state, level);
>  
>  	pwm_ctl = 0;
>  	if (panel->backlight.active_low_pwm)
> @@ -1174,7 +1182,6 @@ static void ext_pwm_enable_backlight(const struct intel_crtc_state *crtc_state,
>  	struct intel_connector *connector = to_intel_connector(conn_state->connector);
>  	struct intel_panel *panel = &connector->panel;
>  
> -	level = intel_panel_compute_brightness(connector, level);
>  	pwm_set_relative_duty_cycle(&panel->backlight.pwm_state, level, 100);
>  	panel->backlight.pwm_state.enabled = true;
>  	pwm_apply_state(panel->backlight.pwm, &panel->backlight.pwm_state);
> @@ -1232,10 +1239,8 @@ static u32 intel_panel_get_backlight(struct intel_connector *connector)
>  
>  	mutex_lock(&dev_priv->backlight_lock);
>  
> -	if (panel->backlight.enabled) {
> +	if (panel->backlight.enabled)
>  		val = panel->backlight.funcs->get(connector);
> -		val = intel_panel_compute_brightness(connector, val);
> -	}
>  
>  	mutex_unlock(&dev_priv->backlight_lock);
>  
> @@ -1566,13 +1571,13 @@ static u32 get_backlight_max_vbt(struct intel_connector *connector)
>  	u16 pwm_freq_hz = get_vbt_pwm_freq(dev_priv);
>  	u32 pwm;
>  
> -	if (!panel->backlight.funcs->hz_to_pwm) {
> +	if (!panel->backlight.pwm_funcs->hz_to_pwm) {
>  		drm_dbg_kms(&dev_priv->drm,
>  			    "backlight frequency conversion not supported\n");
>  		return 0;
>  	}
>  
> -	pwm = panel->backlight.funcs->hz_to_pwm(connector, pwm_freq_hz);
> +	pwm = panel->backlight.pwm_funcs->hz_to_pwm(connector, pwm_freq_hz);
>  	if (!pwm) {
>  		drm_dbg_kms(&dev_priv->drm,
>  			    "backlight frequency conversion failed\n");
> @@ -1591,7 +1596,7 @@ static u32 get_backlight_min_vbt(struct intel_connector *connector)
>  	struct intel_panel *panel = &connector->panel;
>  	int min;
>  
> -	drm_WARN_ON(&dev_priv->drm, panel->backlight.max == 0);
> +	drm_WARN_ON(&dev_priv->drm, panel->backlight.pwm_max == 0);
>  
>  	/*
>  	 * XXX: If the vbt value is 255, it makes min equal to max, which leads
> @@ -1608,7 +1613,7 @@ static u32 get_backlight_min_vbt(struct intel_connector *connector)
>  	}
>  
>  	/* vbt value is a coefficient in range [0..255] */
> -	return scale(min, 0, 255, 0, panel->backlight.max);
> +	return scale(min, 0, 255, 0, panel->backlight.pwm_max);
>  }
>  
>  static int lpt_setup_backlight(struct intel_connector *connector, enum pipe unused)
> @@ -1628,37 +1633,32 @@ static int lpt_setup_backlight(struct intel_connector *connector, enum pipe unus
>  	panel->backlight.active_low_pwm = pch_ctl1 & BLM_PCH_POLARITY;
>  
>  	pch_ctl2 = intel_de_read(dev_priv, BLC_PWM_PCH_CTL2);
> -	panel->backlight.max = pch_ctl2 >> 16;
> +	panel->backlight.pwm_max = pch_ctl2 >> 16;
>  
>  	cpu_ctl2 = intel_de_read(dev_priv, BLC_PWM_CPU_CTL2);
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
> -	panel->backlight.enabled = pch_ctl1 & BLM_PCH_PWM_ENABLE;
> +	panel->backlight.pwm_enabled = pch_ctl1 & BLM_PCH_PWM_ENABLE;
>  
> -	cpu_mode = panel->backlight.enabled && HAS_PCH_LPT(dev_priv) &&
> +	cpu_mode = panel->backlight.pwm_enabled && HAS_PCH_LPT(dev_priv) &&
>  		   !(pch_ctl1 & BLM_PCH_OVERRIDE_ENABLE) &&
>  		   (cpu_ctl2 & BLM_PWM_ENABLE);
> -	if (cpu_mode)
> -		val = pch_get_backlight(connector);
> -	else
> -		val = lpt_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
>  
>  	if (cpu_mode) {
> +		val = intel_panel_sanitize_pwm_level(connector, pch_get_backlight(connector));
> +
>  		drm_dbg_kms(&dev_priv->drm,
>  			    "CPU backlight register was enabled, switching to PCH override\n");
>  
>  		/* Write converted CPU PWM value to PCH override register */
> -		lpt_set_backlight(connector->base.state, panel->backlight.level);
> +		lpt_set_backlight(connector->base.state, val);
>  		intel_de_write(dev_priv, BLC_PWM_PCH_CTL1,
>  			       pch_ctl1 | BLM_PCH_OVERRIDE_ENABLE);
>  
> @@ -1673,29 +1673,24 @@ static int pch_setup_backlight(struct intel_connector *connector, enum pipe unus
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
> -	u32 cpu_ctl2, pch_ctl1, pch_ctl2, val;
> +	u32 cpu_ctl2, pch_ctl1, pch_ctl2;
>  
>  	pch_ctl1 = intel_de_read(dev_priv, BLC_PWM_PCH_CTL1);
>  	panel->backlight.active_low_pwm = pch_ctl1 & BLM_PCH_POLARITY;
>  
>  	pch_ctl2 = intel_de_read(dev_priv, BLC_PWM_PCH_CTL2);
> -	panel->backlight.max = pch_ctl2 >> 16;
> +	panel->backlight.pwm_max = pch_ctl2 >> 16;
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> -
> -	val = pch_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
>  	cpu_ctl2 = intel_de_read(dev_priv, BLC_PWM_CPU_CTL2);
> -	panel->backlight.enabled = (cpu_ctl2 & BLM_PWM_ENABLE) &&
> +	panel->backlight.pwm_enabled = (cpu_ctl2 & BLM_PWM_ENABLE) &&
>  		(pch_ctl1 & BLM_PCH_PWM_ENABLE);
>  
>  	return 0;
> @@ -1715,27 +1710,26 @@ static int i9xx_setup_backlight(struct intel_connector *connector, enum pipe unu
>  	if (IS_PINEVIEW(dev_priv))
>  		panel->backlight.active_low_pwm = ctl & BLM_POLARITY_PNV;
>  
> -	panel->backlight.max = ctl >> 17;
> +	panel->backlight.pwm_max = ctl >> 17;
>  
> -	if (!panel->backlight.max) {
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> -		panel->backlight.max >>= 1;
> +	if (!panel->backlight.pwm_max) {
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
> +		panel->backlight.pwm_max >>= 1;
>  	}
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
>  	if (panel->backlight.combination_mode)
> -		panel->backlight.max *= 0xff;
> +		panel->backlight.pwm_max *= 0xff;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
>  	val = i9xx_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> +	val = intel_panel_sanitize_pwm_level(connector, val);
> +	val = clamp(val, panel->backlight.pwm_min, panel->backlight.pwm_max);
>  
> -	panel->backlight.enabled = val != 0;
> +	panel->backlight.pwm_enabled = val != 0;
>  
>  	return 0;
>  }
> @@ -1744,32 +1738,27 @@ static int i965_setup_backlight(struct intel_connector *connector, enum pipe unu
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
> -	u32 ctl, ctl2, val;
> +	u32 ctl, ctl2;
>  
>  	ctl2 = intel_de_read(dev_priv, BLC_PWM_CTL2);
>  	panel->backlight.combination_mode = ctl2 & BLM_COMBINATION_MODE;
>  	panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965;
>  
>  	ctl = intel_de_read(dev_priv, BLC_PWM_CTL);
> -	panel->backlight.max = ctl >> 16;
> +	panel->backlight.pwm_max = ctl >> 16;
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
>  	if (panel->backlight.combination_mode)
> -		panel->backlight.max *= 0xff;
> -
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> +		panel->backlight.pwm_max *= 0xff;
>  
> -	val = i9xx_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
> -	panel->backlight.enabled = ctl2 & BLM_PWM_ENABLE;
> +	panel->backlight.pwm_enabled = ctl2 & BLM_PWM_ENABLE;
>  
>  	return 0;
>  }
> @@ -1778,7 +1767,7 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
> -	u32 ctl, ctl2, val;
> +	u32 ctl, ctl2;
>  
>  	if (drm_WARN_ON(&dev_priv->drm, pipe != PIPE_A && pipe != PIPE_B))
>  		return -ENODEV;
> @@ -1787,22 +1776,17 @@ static int vlv_setup_backlight(struct intel_connector *connector, enum pipe pipe
>  	panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965;
>  
>  	ctl = intel_de_read(dev_priv, VLV_BLC_PWM_CTL(pipe));
> -	panel->backlight.max = ctl >> 16;
> +	panel->backlight.pwm_max = ctl >> 16;
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> -
> -	val = _vlv_get_backlight(dev_priv, pipe);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
> -	panel->backlight.enabled = ctl2 & BLM_PWM_ENABLE;
> +	panel->backlight.pwm_enabled = ctl2 & BLM_PWM_ENABLE;
>  
>  	return 0;
>  }
> @@ -1827,24 +1811,18 @@ bxt_setup_backlight(struct intel_connector *connector, enum pipe unused)
>  	}
>  
>  	panel->backlight.active_low_pwm = pwm_ctl & BXT_BLC_PWM_POLARITY;
> -	panel->backlight.max =
> -		intel_de_read(dev_priv,
> -			      BXT_BLC_PWM_FREQ(panel->backlight.controller));
> +	panel->backlight.pwm_max = intel_de_read(dev_priv,
> +						 BXT_BLC_PWM_FREQ(panel->backlight.controller));
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
> -	val = bxt_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> -
> -	panel->backlight.enabled = pwm_ctl & BXT_BLC_PWM_ENABLE;
> +	panel->backlight.pwm_enabled = pwm_ctl & BXT_BLC_PWM_ENABLE;
>  
>  	return 0;
>  }
> @@ -1854,7 +1832,7 @@ cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  	struct intel_panel *panel = &connector->panel;
> -	u32 pwm_ctl, val;
> +	u32 pwm_ctl;
>  
>  	/*
>  	 * CNP has the BXT implementation of backlight, but with only one
> @@ -1867,24 +1845,18 @@ cnp_setup_backlight(struct intel_connector *connector, enum pipe unused)
>  				BXT_BLC_PWM_CTL(panel->backlight.controller));
>  
>  	panel->backlight.active_low_pwm = pwm_ctl & BXT_BLC_PWM_POLARITY;
> -	panel->backlight.max =
> -		intel_de_read(dev_priv,
> -			      BXT_BLC_PWM_FREQ(panel->backlight.controller));
> +	panel->backlight.pwm_max = intel_de_read(dev_priv,
> +						 BXT_BLC_PWM_FREQ(panel->backlight.controller));
>  
> -	if (!panel->backlight.max)
> -		panel->backlight.max = get_backlight_max_vbt(connector);
> +	if (!panel->backlight.pwm_max)
> +		panel->backlight.pwm_max = get_backlight_max_vbt(connector);
>  
> -	if (!panel->backlight.max)
> +	if (!panel->backlight.pwm_max)
>  		return -ENODEV;
>  
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> -
> -	val = bxt_get_backlight(connector);
> -	val = intel_panel_compute_brightness(connector, val);
> -	panel->backlight.level = clamp(val, panel->backlight.min,
> -				       panel->backlight.max);
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
> -	panel->backlight.enabled = pwm_ctl & BXT_BLC_PWM_ENABLE;
> +	panel->backlight.pwm_enabled = pwm_ctl & BXT_BLC_PWM_ENABLE;
>  
>  	return 0;
>  }
> @@ -1914,8 +1886,8 @@ static int ext_pwm_setup_backlight(struct intel_connector *connector,
>  		return -ENODEV;
>  	}
>  
> -	panel->backlight.max = 100; /* 100% */
> -	panel->backlight.min = get_backlight_min_vbt(connector);
> +	panel->backlight.pwm_max = 100; /* 100% */
> +	panel->backlight.pwm_min = get_backlight_min_vbt(connector);
>  
>  	if (pwm_is_enabled(panel->backlight.pwm)) {
>  		/* PWM is already enabled, use existing settings */
> @@ -1923,10 +1895,8 @@ static int ext_pwm_setup_backlight(struct intel_connector *connector,
>  
>  		level = pwm_get_relative_duty_cycle(&panel->backlight.pwm_state,
>  						    100);
> -		level = intel_panel_compute_brightness(connector, level);
> -		panel->backlight.level = clamp(level, panel->backlight.min,
> -					       panel->backlight.max);
> -		panel->backlight.enabled = true;
> +		level = intel_panel_sanitize_pwm_level(connector, level);
> +		panel->backlight.pwm_enabled = true;
>  
>  		drm_dbg_kms(&dev_priv->drm, "PWM already enabled at freq %ld, VBT freq %d, level %d\n",
>  			    NSEC_PER_SEC / (unsigned long)panel->backlight.pwm_state.period,
> @@ -1942,6 +1912,61 @@ static int ext_pwm_setup_backlight(struct intel_connector *connector,
>  	return 0;
>  }
>  
> +static void intel_pwm_set_backlight(const struct drm_connector_state *conn_state, u32 level)
> +{
> +	struct intel_connector *connector = to_intel_connector(conn_state->connector);
> +	struct intel_panel *panel = &connector->panel;
> +
> +	panel->backlight.pwm_funcs->set(conn_state,
> +				       intel_panel_sanitize_pwm_level(connector, level));
> +}
> +
> +static u32 intel_pwm_get_backlight(struct intel_connector *connector)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +
> +	return intel_panel_sanitize_pwm_level(connector,
> +					      panel->backlight.pwm_funcs->get(connector));
> +}
> +
> +static void intel_pwm_enable_backlight(const struct intel_crtc_state *crtc_state,
> +				       const struct drm_connector_state *conn_state, u32 level)
> +{
> +	struct intel_connector *connector = to_intel_connector(conn_state->connector);
> +	struct intel_panel *panel = &connector->panel;
> +
> +	panel->backlight.pwm_funcs->enable(crtc_state, conn_state,
> +					   intel_panel_sanitize_pwm_level(connector, level));
> +}
> +
> +static void intel_pwm_disable_backlight(const struct drm_connector_state *conn_state, u32 level)
> +{
> +	struct intel_connector *connector = to_intel_connector(conn_state->connector);
> +	struct intel_panel *panel = &connector->panel;
> +
> +	panel->backlight.pwm_funcs->disable(conn_state,
> +					    intel_panel_sanitize_pwm_level(connector, level));
> +}
> +
> +/* The only hook PWM-only backlight setups need to override, the rest of the hooks are filled in
> + * from pwm_funcs
> + */

Isn't this comment stale now?

> +static int intel_pwm_setup_backlight(struct intel_connector *connector, enum pipe pipe)
> +{
> +	struct intel_panel *panel = &connector->panel;
> +	int ret = panel->backlight.pwm_funcs->setup(connector, pipe);
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	panel->backlight.min = panel->backlight.pwm_min;
> +	panel->backlight.max = panel->backlight.pwm_max;
> +	panel->backlight.level = panel->backlight.funcs->get(connector);

Brain hurts with the two value "domains". I'm wondering if we should
start to follow some naming convention, for example "pwm_val" or
"pwm_level" for everything that is in the "pwm domain". It would be
easier to follow.

Perhaps the level should be set with just direct
intel_pwm_get_backlight() to avoid an unnecessary indirection here?

> +	panel->backlight.enabled = panel->backlight.pwm_enabled;
> +
> +	return 0;
> +}
> +
>  void intel_panel_update_backlight(struct intel_atomic_state *state,
>  				  struct intel_encoder *encoder,
>  				  const struct intel_crtc_state *crtc_state,
> @@ -2015,7 +2040,7 @@ static void intel_panel_destroy_backlight(struct intel_panel *panel)
>  	panel->backlight.present = false;
>  }
>  
> -static const struct intel_panel_bl_funcs bxt_funcs = {
> +static const struct intel_panel_bl_funcs bxt_pwm_funcs = {
>  	.setup = bxt_setup_backlight,
>  	.enable = bxt_enable_backlight,
>  	.disable = bxt_disable_backlight,
> @@ -2024,7 +2049,7 @@ static const struct intel_panel_bl_funcs bxt_funcs = {
>  	.hz_to_pwm = bxt_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs cnp_funcs = {
> +static const struct intel_panel_bl_funcs cnp_pwm_funcs = {
>  	.setup = cnp_setup_backlight,
>  	.enable = cnp_enable_backlight,
>  	.disable = cnp_disable_backlight,
> @@ -2033,7 +2058,7 @@ static const struct intel_panel_bl_funcs cnp_funcs = {
>  	.hz_to_pwm = cnp_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs lpt_funcs = {
> +static const struct intel_panel_bl_funcs lpt_pwm_funcs = {
>  	.setup = lpt_setup_backlight,
>  	.enable = lpt_enable_backlight,
>  	.disable = lpt_disable_backlight,
> @@ -2042,7 +2067,7 @@ static const struct intel_panel_bl_funcs lpt_funcs = {
>  	.hz_to_pwm = lpt_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs spt_funcs = {
> +static const struct intel_panel_bl_funcs spt_pwm_funcs = {
>  	.setup = lpt_setup_backlight,
>  	.enable = lpt_enable_backlight,
>  	.disable = lpt_disable_backlight,
> @@ -2051,7 +2076,7 @@ static const struct intel_panel_bl_funcs spt_funcs = {
>  	.hz_to_pwm = spt_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs pch_funcs = {
> +static const struct intel_panel_bl_funcs pch_pwm_funcs = {
>  	.setup = pch_setup_backlight,
>  	.enable = pch_enable_backlight,
>  	.disable = pch_disable_backlight,
> @@ -2068,7 +2093,7 @@ static const struct intel_panel_bl_funcs ext_pwm_funcs = {
>  	.get = ext_pwm_get_backlight,
>  };
>  
> -static const struct intel_panel_bl_funcs vlv_funcs = {
> +static const struct intel_panel_bl_funcs vlv_pwm_funcs = {
>  	.setup = vlv_setup_backlight,
>  	.enable = vlv_enable_backlight,
>  	.disable = vlv_disable_backlight,
> @@ -2077,7 +2102,7 @@ static const struct intel_panel_bl_funcs vlv_funcs = {
>  	.hz_to_pwm = vlv_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs i965_funcs = {
> +static const struct intel_panel_bl_funcs i965_pwm_funcs = {
>  	.setup = i965_setup_backlight,
>  	.enable = i965_enable_backlight,
>  	.disable = i965_disable_backlight,
> @@ -2086,7 +2111,7 @@ static const struct intel_panel_bl_funcs i965_funcs = {
>  	.hz_to_pwm = i965_hz_to_pwm,
>  };
>  
> -static const struct intel_panel_bl_funcs i9xx_funcs = {
> +static const struct intel_panel_bl_funcs i9xx_pwm_funcs = {
>  	.setup = i9xx_setup_backlight,
>  	.enable = i9xx_enable_backlight,
>  	.disable = i9xx_disable_backlight,
> @@ -2095,6 +2120,14 @@ static const struct intel_panel_bl_funcs i9xx_funcs = {
>  	.hz_to_pwm = i9xx_hz_to_pwm,
>  };
>  
> +static const struct intel_panel_bl_funcs pwm_bl_funcs = {
> +	.setup = intel_pwm_setup_backlight,
> +	.enable = intel_pwm_enable_backlight,
> +	.disable = intel_pwm_disable_backlight,
> +	.set = intel_pwm_set_backlight,
> +	.get = intel_pwm_get_backlight,
> +};
> +
>  /* Set up chip specific backlight functions */
>  static void
>  intel_panel_init_backlight_funcs(struct intel_panel *panel)
> @@ -2103,36 +2136,39 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
>  		container_of(panel, struct intel_connector, panel);
>  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>  
> -	if (connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
> -	    intel_dp_aux_init_backlight_funcs(connector) == 0)
> -		return;
> -

I think I'd keep this here in this patch. It helps with the
interpretation of the change here, i.e. we're not starting to utilize
the two levels just yet.

>  	if (connector->base.connector_type == DRM_MODE_CONNECTOR_DSI &&
>  	    intel_dsi_dcs_init_backlight_funcs(connector) == 0)
>  		return;
>  
>  	if (IS_GEN9_LP(dev_priv)) {
> -		panel->backlight.funcs = &bxt_funcs;
> +		panel->backlight.pwm_funcs = &bxt_pwm_funcs;
>  	} else if (INTEL_PCH_TYPE(dev_priv) >= PCH_CNP) {
> -		panel->backlight.funcs = &cnp_funcs;
> +		panel->backlight.pwm_funcs = &cnp_pwm_funcs;
>  	} else if (INTEL_PCH_TYPE(dev_priv) >= PCH_LPT) {
>  		if (HAS_PCH_LPT(dev_priv))
> -			panel->backlight.funcs = &lpt_funcs;
> +			panel->backlight.pwm_funcs = &lpt_pwm_funcs;
>  		else
> -			panel->backlight.funcs = &spt_funcs;
> +			panel->backlight.pwm_funcs = &spt_pwm_funcs;
>  	} else if (HAS_PCH_SPLIT(dev_priv)) {
> -		panel->backlight.funcs = &pch_funcs;
> +		panel->backlight.pwm_funcs = &pch_pwm_funcs;
>  	} else if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) {
>  		if (connector->base.connector_type == DRM_MODE_CONNECTOR_DSI) {
> -			panel->backlight.funcs = &ext_pwm_funcs;
> +			panel->backlight.pwm_funcs = &ext_pwm_funcs;
>  		} else {
> -			panel->backlight.funcs = &vlv_funcs;
> +			panel->backlight.pwm_funcs = &vlv_pwm_funcs;
>  		}
>  	} else if (IS_GEN(dev_priv, 4)) {
> -		panel->backlight.funcs = &i965_funcs;
> +		panel->backlight.pwm_funcs = &i965_pwm_funcs;
>  	} else {
> -		panel->backlight.funcs = &i9xx_funcs;
> +		panel->backlight.pwm_funcs = &i9xx_pwm_funcs;
>  	}
> +
> +	if (connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
> +	    intel_dp_aux_init_backlight_funcs(connector) == 0)
> +		return;
> +
> +	/* We're using a standard PWM backlight interface */
> +	panel->backlight.funcs = &pwm_bl_funcs;
>  }
>  
>  enum drm_connector_status

-- 
Jani Nikula, Intel Open Source Graphics Center