Re: [PATCH v5 1/4] drm/i915: Keep track of pwm-related backlight hooks separately

[Vasily Khoruzhick <anarsoul@gmail.com>]

On Thu, Jan 7, 2021 at 2:52 PM Lyude Paul <lyude@redhat.com> 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 CPU mode, and switching
> to PCH mode. The reason for 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 switching from CPU mode to PCH, but 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.
>
> v5:
> * Fix indenting warnings from checkpatch
> v4:
> * Fix commit message
> * Remove outdated comment in intel_panel.c
> * Rename pwm_(min|max) to pwm_level_(min|max)
> * Use intel_pwm_get_backlight() in intel_pwm_setup_backlight() instead of
>   indirection
> * Don't move intel_dp_aux_init_bcklight_funcs() call to bottom of
>   intel_panel_init_backlight_funcs() quite yet
> v3:
> * Reuse intel_panel_bl_funcs() for pwm_funcs
> * Explain why we drop lpt_get_backlight()
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: thaytan@noraisin.net
> Cc: Vasily Khoruzhick <anarsoul@gmail.com>

Whole series is:

Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>

> ---
>  .../drm/i915/display/intel_display_types.h    |   4 +
>  drivers/gpu/drm/i915/display/intel_panel.c    | 333 ++++++++++--------
>  2 files changed, 187 insertions(+), 150 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 1067bd073c95..ee5c2d50b81a 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_level_min;
> +               u32 pwm_level_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..8c99bf404a32 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_level_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_level_max - val + panel->backlight.pwm_level_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_level_max == 0);
>
>         if (panel->backlight.combination_mode) {
>                 u8 lbpc;
>
> -               lbpc = level * 0xfe / panel->backlight.max + 1;
> +               lbpc = level * 0xfe / panel->backlight.pwm_level_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_level_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_level_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_level_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_level_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_level_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_level_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_level_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_level_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_level_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_level_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_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_max)
>                 return -ENODEV;
>
> -       panel->backlight.min = get_backlight_min_vbt(connector);
> +       panel->backlight.pwm_level_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_level_max = pch_ctl2 >> 16;
>
> -       if (!panel->backlight.max)
> -               panel->backlight.max = get_backlight_max_vbt(connector);
> +       if (!panel->backlight.pwm_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_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_level_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_level_max = ctl >> 17;
>
> -       if (!panel->backlight.max) {
> -               panel->backlight.max = get_backlight_max_vbt(connector);
> -               panel->backlight.max >>= 1;
> +       if (!panel->backlight.pwm_level_max) {
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
> +               panel->backlight.pwm_level_max >>= 1;
>         }
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_max)
>                 return -ENODEV;
>
>         if (panel->backlight.combination_mode)
> -               panel->backlight.max *= 0xff;
> +               panel->backlight.pwm_level_max *= 0xff;
>
> -       panel->backlight.min = get_backlight_min_vbt(connector);
> +       panel->backlight.pwm_level_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_level_min, panel->backlight.pwm_level_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_level_max = ctl >> 16;
>
> -       if (!panel->backlight.max)
> -               panel->backlight.max = get_backlight_max_vbt(connector);
> +       if (!panel->backlight.pwm_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_max)
>                 return -ENODEV;
>
>         if (panel->backlight.combination_mode)
> -               panel->backlight.max *= 0xff;
> -
> -       panel->backlight.min = get_backlight_min_vbt(connector);
> +               panel->backlight.pwm_level_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_level_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_level_max = ctl >> 16;
>
> -       if (!panel->backlight.max)
> -               panel->backlight.max = get_backlight_max_vbt(connector);
> +       if (!panel->backlight.pwm_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_max)
>                 return -ENODEV;
>
> -       panel->backlight.min = get_backlight_min_vbt(connector);
> +       panel->backlight.pwm_level_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.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_level_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_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_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_level_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;
>  }
> @@ -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_level_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_level_max)
> +               panel->backlight.pwm_level_max = get_backlight_max_vbt(connector);
>
> -       if (!panel->backlight.max)
> +       if (!panel->backlight.pwm_level_max)
>                 return -ENODEV;
>
> -       panel->backlight.min = get_backlight_min_vbt(connector);
> +       panel->backlight.pwm_level_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;
>  }
> @@ -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_level_max = 100; /* 100% */
> +       panel->backlight.pwm_level_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 +1912,58 @@ 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));
> +}
> +
> +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_level_min;
> +       panel->backlight.max = panel->backlight.pwm_level_max;
> +       panel->backlight.level = intel_pwm_get_backlight(connector);
> +       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 +2037,7 @@ 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 +2046,7 @@ 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 +2055,7 @@ 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 +2064,7 @@ 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 +2073,7 @@ 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 +2090,7 @@ 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 +2099,7 @@ 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 +2108,7 @@ 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 +2117,14 @@ 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)
> @@ -2112,27 +2142,30 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
>                 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;
>         }
> +
> +       /* We're using a standard PWM backlight interface */
> +       panel->backlight.funcs = &pwm_bl_funcs;
>  }
>
>  enum drm_connector_status
> --
> 2.29.2
>