Re: [v8 1/6] drm/panel: add basic DP AUX backlight support

Am 26.06.21 um 18:51 schrieb Rajeev Nandan:

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 rajeevny@codeaurora.org Reviewed-by: Douglas Anderson dianders@chromium.org Reviewed-by: Lyude Paul lyude@redhat.com

---

Changes in v5:

• New

Changes in v6:

• Fixed ordering of memory allocation (Douglas)
• Updated word wrapping in a comment (Douglas)

Changes in v8:

• Now using backlight_is_blank() to get the backlight blank status (Sam Ravnborg)

  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..4fa1e3b 100644 --- a/drivers/gpu/drm/drm_panel.c +++ b/drivers/gpu/drm/drm_panel.c @@ -26,12 +26,20 @@ #include <linux/module.h>

#include <drm/drm_crtc.h> +#include <drm/drm_dp_helper.h> #include <drm/drm_panel.h> #include <drm/drm_print.h>

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 (!backlight_is_blank(bd)) {

• 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);
  

This creates a cyclic dependency between drm_kms_helper-ko and drm.ko. drm_panel.c is in the latter, while drm_dp_dpcd_read() in drm_dp_helper.c is in the former. Please fix.

Best regards Thomas

• 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,

• 		     &current_level, &current_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 treding@nvidia.com"); 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