Re: [PATCH v10 2/3] drm/i915: Add option to support dynamic backlight via DPCD

[Puthikorn Voravootivat <puthik@xxxxxxxxxxxx>]

On Fri, Jun 2, 2017 at 11:25 AM, Pandiyan, Dhinakaran <dhinakaran.pandiyan@xxxxxxxxx> wrote:

On Fri, 2017-05-26 at 18:42 -0700, Puthikorn Voravootivat wrote:

> This patch adds option to enable dynamic backlight for eDP
> panel that supports this feature via DPCD register and
> set minimum / maximum brightness to 0% and 100% of the
> normal brightness.
>
> Signed-off-by: Puthikorn Voravootivat <puthik@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/i915_params.c            |  5 ++++
>  drivers/gpu/drm/i915/i915_params.h            |  3 +-
>  drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 42 ++++++++++++++++++++++-----
>  3 files changed, 41 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 3758ae1f11b4..ce033d58134e 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -65,6 +65,7 @@ struct i915_params i915 __read_mostly = {
>       .inject_load_failure = 0,
>       .enable_dpcd_backlight = -1,
>       .enable_gvt = false,
> +     .enable_dbc = false,
>  };
>
>  module_param_named(modeset, i915.modeset, int, 0400);
> @@ -254,3 +255,7 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
>  module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
>  MODULE_PARM_DESC(enable_gvt,
>       "Enable support for Intel GVT-g graphics virtualization host support(default:false)");
> +
> +module_param_named_unsafe(enable_dbc, i915.enable_dbc, bool, 0600);
> +MODULE_PARM_DESC(enable_dbc,
> +     "Enable support for dynamic backlight control (default:false)");
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index ac02efce6e22..2de3e2850b54 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -67,7 +67,8 @@
>       func(bool, nuclear_pageflip); \
>       func(bool, enable_dp_mst); \
>       func(int, enable_dpcd_backlight); \
> -     func(bool, enable_gvt)
> +     func(bool, enable_gvt); \
> +     func(bool, enable_dbc)
>
>  #define MEMBER(T, member) T member
>  struct i915_params {
> diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> index c89aae804659..f55af41ce3bd 100644
> --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> @@ -100,11 +100,26 @@ intel_dp_aux_set_backlight(struct intel_connector *connector, u32 level)
>       }
>  }
>
> +/*
> + * Set minimum / maximum dynamic brightness percentage. This value is expressed
> + * as the percentage of normal brightness in 5% increments.
> + */
> +static void
> +intel_dp_aux_set_dynamic_backlight_percent(struct intel_dp *intel_dp,
> +                                        u32 min, u32 max)
> +{
> +     u8 dbc[] = { DIV_ROUND_CLOSEST(min, 5), DIV_ROUND_CLOSEST(max, 5) };
> +
> +     if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_DBC_MINIMUM_BRIGHTNESS_SET,
> +                       dbc, sizeof(dbc)) < 0) {
> +             DRM_DEBUG_KMS("Failed to write aux DBC brightness level\n");
> +     }
> +}
> +
>  static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
>  {
>       struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
> -     uint8_t dpcd_buf = 0;
> -     uint8_t edp_backlight_mode = 0;
> +     uint8_t dpcd_buf, new_dpcd_buf, edp_backlight_mode;
>
>       if (drm_dp_dpcd_readb(&intel_dp->aux,
>                       DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf) != 1) {
> @@ -113,18 +128,15 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
>               return;
>       }
>
> +     new_dpcd_buf = dpcd_buf;
>       edp_backlight_mode = dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
>
>       switch (edp_backlight_mode) {
>       case DP_EDP_BACKLIGHT_CONTROL_MODE_PWM:
>       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET:
>       case DP_EDP_BACKLIGHT_CONTROL_MODE_PRODUCT:
> -             dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> -             dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
> -             if (drm_dp_dpcd_writeb(&intel_dp->aux,
> -                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf) < 0) {
> -                     DRM_DEBUG_KMS("Failed to write aux backlight mode\n");
> -             }
> +             new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK;
> +             new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD;
>               break;
>
>       /* Do nothing when it is already DPCD mode */
> @@ -133,6 +145,20 @@ static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
>               break;
>       }
>
> +     if (i915.enable_dbc &&
> +         (intel_dp->edp_dpcd[2] & DP_EDP_DYNAMIC_BACKLIGHT_CAP)) {
> +             new_dpcd_buf |= DP_EDP_DYNAMIC_BACKLIGHT_ENABLE;
> +             intel_dp_aux_set_dynamic_backlight_percent(intel_dp, 0, 100);
> +             DRM_DEBUG_KMS("Enable dynamic brightness.\n");
> +     }
> +

Just curious, does DBC require DP AUX brightness control?

No. Here is quote from the spec.

"The Dynamic Backlight Control (DBC) and color engine modes are not listed in Table 10-1,

because when they are available, they are available for all supported modes."

 

-DK

> +     if (new_dpcd_buf != dpcd_buf) {
> +             if (drm_dp_dpcd_writeb(&intel_dp->aux,
> +                     DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf) < 0) {
> +                     DRM_DEBUG_KMS("Failed to write aux backlight mode\n");
> +             }
> +     }
> +
>       set_aux_backlight_enable(intel_dp, true);
>       intel_dp_aux_set_backlight(connector, connector->panel.backlight.level);
>  }

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