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[108.49.102.102]) by smtp.gmail.com with ESMTPSA id s22sm1708411qtx.32.2021.06.16.12.22.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Jun 2021 12:22:27 -0700 (PDT) Message-ID: <31f31a0d37e05f71ade68b3452ef471c0c681302.camel@redhat.com> Subject: Re: [v6 1/5] drm/panel: add basic DP AUX backlight support From: Lyude Paul To: Rajeev Nandan , dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, devicetree@vger.kernel.org Cc: linux-kernel@vger.kernel.org, thierry.reding@gmail.com, sam@ravnborg.org, robdclark@gmail.com, dianders@chromium.org, jani.nikula@intel.com, robh@kernel.org, laurent.pinchart@ideasonboard.com, a.hajda@samsung.com, daniel.thompson@linaro.org, hoegsberg@chromium.org, abhinavk@codeaurora.org, seanpaul@chromium.org, kalyan_t@codeaurora.org, mkrishn@codeaurora.org, lee.jones@linaro.org, jingoohan1@gmail.com, linux-fbdev@vger.kernel.org Date: Wed, 16 Jun 2021 15:22:25 -0400 In-Reply-To: <1623499682-2140-2-git-send-email-rajeevny@codeaurora.org> References: <1623499682-2140-1-git-send-email-rajeevny@codeaurora.org> <1623499682-2140-2-git-send-email-rajeevny@codeaurora.org> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.4 (3.38.4-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reviewed-by: Lyude Paul On Sat, 2021-06-12 at 17:37 +0530, Rajeev Nandan wrote: > Some panels support backlight control over DP AUX channel using > VESA's standard backlight control interface. > Using new DRM eDP backlight helpers, add support to create and > register a backlight for those panels in drm_panel to simplify > the panel drivers. > > The panel driver with access to "struct drm_dp_aux" can create and > register a backlight device using following code snippet in its > probe() function: > >         err = drm_panel_dp_aux_backlight(panel, aux); >         if (err) >                 return err; > > Then drm_panel will handle backlight_(enable|disable) calls > similar to the case when drm_panel_of_backlight() is used. > > Currently, we are not supporting one feature where the source > device can combine the backlight brightness levels set through > DP AUX and the BL_PWM_DIM eDP connector pin. Since it's not > required for the basic backlight controls, it can be added later. > > Signed-off-by: Rajeev Nandan > Reviewed-by: Douglas Anderson > --- > > Changes in v5: > - New > > Changes in v6: > - Fixed ordering of memory allocation (Douglas) > - Updated word wrapping in a comment (Douglas) > >  drivers/gpu/drm/drm_panel.c | 108 > ++++++++++++++++++++++++++++++++++++++++++++ >  include/drm/drm_panel.h     |  15 ++++-- >  2 files changed, 119 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c > index f634371..9e65342 100644 > --- a/drivers/gpu/drm/drm_panel.c > +++ b/drivers/gpu/drm/drm_panel.c > @@ -26,12 +26,20 @@ >  #include >   >  #include > +#include >  #include >  #include >   >  static DEFINE_MUTEX(panel_lock); >  static LIST_HEAD(panel_list); >   > +struct dp_aux_backlight { > +       struct backlight_device *base; > +       struct drm_dp_aux *aux; > +       struct drm_edp_backlight_info info; > +       bool enabled; > +}; > + >  /** >   * DOC: drm panel >   * > @@ -342,6 +350,106 @@ int drm_panel_of_backlight(struct drm_panel *panel) >         return 0; >  } >  EXPORT_SYMBOL(drm_panel_of_backlight); > + > +static int dp_aux_backlight_update_status(struct backlight_device *bd) > +{ > +       struct dp_aux_backlight *bl = bl_get_data(bd); > +       u16 brightness = backlight_get_brightness(bd); > +       int ret = 0; > + > +       if (brightness > 0) { > +               if (!bl->enabled) { > +                       drm_edp_backlight_enable(bl->aux, &bl->info, > brightness); > +                       bl->enabled = true; > +                       return 0; > +               } > +               ret = drm_edp_backlight_set_level(bl->aux, &bl->info, > brightness); > +       } else { > +               if (bl->enabled) { > +                       drm_edp_backlight_disable(bl->aux, &bl->info); > +                       bl->enabled = false; > +               } > +       } > + > +       return ret; > +} > + > +static const struct backlight_ops dp_aux_bl_ops = { > +       .update_status = dp_aux_backlight_update_status, > +}; > + > +/** > + * drm_panel_dp_aux_backlight - create and use DP AUX backlight > + * @panel: DRM panel > + * @aux: The DP AUX channel to use > + * > + * Use this function to create and handle backlight if your panel > + * supports backlight control over DP AUX channel using DPCD > + * registers as per VESA's standard backlight control interface. > + * > + * When the panel is enabled backlight will be enabled after a > + * successful call to &drm_panel_funcs.enable() > + * > + * When the panel is disabled backlight will be disabled before the > + * call to &drm_panel_funcs.disable(). > + * > + * A typical implementation for a panel driver supporting backlight > + * control over DP AUX will call this function at probe time. > + * Backlight will then be handled transparently without requiring > + * any intervention from the driver. > + * > + * drm_panel_dp_aux_backlight() must be called after the call to > drm_panel_init(). > + * > + * Return: 0 on success or a negative error code on failure. > + */ > +int drm_panel_dp_aux_backlight(struct drm_panel *panel, struct drm_dp_aux > *aux) > +{ > +       struct dp_aux_backlight *bl; > +       struct backlight_properties props = { 0 }; > +       u16 current_level; > +       u8 current_mode; > +       u8 edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE]; > +       int ret; > + > +       if (!panel || !panel->dev || !aux) > +               return -EINVAL; > + > +       ret = drm_dp_dpcd_read(aux, DP_EDP_DPCD_REV, edp_dpcd, > +                              EDP_DISPLAY_CTL_CAP_SIZE); > +       if (ret < 0) > +               return ret; > + > +       if (!drm_edp_backlight_supported(edp_dpcd)) { > +               DRM_DEV_INFO(panel->dev, "DP AUX backlight is not > supported\n"); > +               return 0; > +       } > + > +       bl = devm_kzalloc(panel->dev, sizeof(*bl), GFP_KERNEL); > +       if (!bl) > +               return -ENOMEM; > + > +       bl->aux = aux; > + > +       ret = drm_edp_backlight_init(aux, &bl->info, 0, edp_dpcd, > +                                    ¤t_level, ¤t_mode); > +       if (ret < 0) > +               return ret; > + > +       props.type = BACKLIGHT_RAW; > +       props.brightness = current_level; > +       props.max_brightness = bl->info.max; > + > +       bl->base = devm_backlight_device_register(panel->dev, > "dp_aux_backlight", > +                                                 panel->dev, bl, > +                                                 &dp_aux_bl_ops, &props); > +       if (IS_ERR(bl->base)) > +               return PTR_ERR(bl->base); > + > +       panel->backlight = bl->base; > + > +       return 0; > +} > +EXPORT_SYMBOL(drm_panel_dp_aux_backlight); >  #endif >   >  MODULE_AUTHOR("Thierry Reding "); > diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h > index 33605c3..3ebfaa6 100644 > --- a/include/drm/drm_panel.h > +++ b/include/drm/drm_panel.h > @@ -32,6 +32,7 @@ struct backlight_device; >  struct device_node; >  struct drm_connector; >  struct drm_device; > +struct drm_dp_aux; >  struct drm_panel; >  struct display_timing; >   > @@ -64,8 +65,8 @@ enum drm_panel_orientation; >   * the panel. This is the job of the .unprepare() function. >   * >   * Backlight can be handled automatically if configured using > - * drm_panel_of_backlight(). Then the driver does not need to implement the > - * functionality to enable/disable backlight. > + * drm_panel_of_backlight() or drm_panel_dp_aux_backlight(). Then the > driver > + * does not need to implement the functionality to enable/disable > backlight. >   */ >  struct drm_panel_funcs { >         /** > @@ -144,8 +145,8 @@ struct drm_panel { >          * Backlight device, used to turn on backlight after the call >          * to enable(), and to turn off backlight before the call to >          * disable(). > -        * backlight is set by drm_panel_of_backlight() and drivers > -        * shall not assign it. > +        * backlight is set by drm_panel_of_backlight() or > +        * drm_panel_dp_aux_backlight() and drivers shall not assign it. >          */ >         struct backlight_device *backlight; >   > @@ -208,11 +209,17 @@ static inline int of_drm_get_panel_orientation(const > struct device_node *np, >  #if IS_ENABLED(CONFIG_DRM_PANEL) && > (IS_BUILTIN(CONFIG_BACKLIGHT_CLASS_DEVICE) || \ >         (IS_MODULE(CONFIG_DRM) && IS_MODULE(CONFIG_BACKLIGHT_CLASS_DEVICE))) >  int drm_panel_of_backlight(struct drm_panel *panel); > +int drm_panel_dp_aux_backlight(struct drm_panel *panel, struct drm_dp_aux > *aux); >  #else >  static inline int drm_panel_of_backlight(struct drm_panel *panel) >  { >         return 0; >  } > +static inline int drm_panel_dp_aux_backlight(struct drm_panel *panel, > +                                            struct drm_dp_aux *aux) > +{ > +       return 0; > +} >  #endif >   >  #endif -- Cheers, Lyude Paul (she/her) Software Engineer at Red Hat