drm/i915/vbt: Fix backlight parsing for VBT 234+

Child min_brightness is obsolete from VBT 234+, instead the new
min_brightness field in the main structure should be used.

This new field is 16 bits wide, so backlight_precision_bits is needed
to check if value needs to be scaled down but it is only available in
VBT 236+ so working around it by using the also new backlight_level
in the main struct.

v2:
- missed that backlight_data->level is also obsolete

v3:
- s/backlight/brightness to better match specification
- using u16 to specify brightness level instead of a u32 : 16

BSpec: 20149
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201008211932.24989-1-jose.souza@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 5804eb9..b4d99d0 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -425,6 +425,7 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv,
        const struct bdb_lfp_backlight_data *backlight_data;
        const struct lfp_backlight_data_entry *entry;
        int panel_type = dev_priv->vbt.panel_type;
+       u16 level;
 
        backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
        if (!backlight_data)
@@ -459,14 +460,39 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv,
 
        dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
        dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
-       dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
+
+       if (bdb->version >= 234) {
+               u16 min_level;
+               bool scale;
+
+               level = backlight_data->brightness_level[panel_type].level;
+               min_level = backlight_data->brightness_min_level[panel_type].level;
+
+               if (bdb->version >= 236)
+                       scale = backlight_data->brightness_precision_bits[panel_type] == 16;
+               else
+                       scale = level > 255;
+
+               if (scale)
+                       min_level = min_level / 255;
+
+               if (min_level > 255) {
+                       drm_warn(&dev_priv->drm, "Brightness min level > 255\n");
+                       level = 255;
+               }
+               dev_priv->vbt.backlight.min_brightness = min_level;
+       } else {
+               level = backlight_data->level[panel_type];
+               dev_priv->vbt.backlight.min_brightness = entry->min_brightness;
+       }
+
        drm_dbg_kms(&dev_priv->drm,
                    "VBT backlight PWM modulation frequency %u Hz, "
                    "active %s, min brightness %u, level %u, controller %u\n",
                    dev_priv->vbt.backlight.pwm_freq_hz,
                    dev_priv->vbt.backlight.active_low_pwm ? "low" : "high",
                    dev_priv->vbt.backlight.min_brightness,
-                   backlight_data->level[panel_type],
+                   level,
                    dev_priv->vbt.backlight.controller);
 }
 

diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
index 54bcc6a..5df23e1 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_vbt_defs.h
+++ b/drivers/gpu/drm/i915/display/intel_vbt_defs.h
@@ -782,7 +782,7 @@ struct lfp_backlight_data_entry {
        u8 active_low_pwm:1;
        u8 obsolete1:5;
        u16 pwm_freq_hz;
-       u8 min_brightness;
+       u8 min_brightness; /* Obsolete from 234+ */
        u8 obsolete2;
        u8 obsolete3;
 } __packed;
@@ -792,11 +792,19 @@ struct lfp_backlight_control_method {
        u8 controller:4;
 } __packed;
 
+struct lfp_brightness_level {
+       u16 level;
+       u16 reserved;
+} __packed;
+
 struct bdb_lfp_backlight_data {
        u8 entry_size;
        struct lfp_backlight_data_entry data[16];
-       u8 level[16];
+       u8 level[16]; /* Obsolete from 234+ */
        struct lfp_backlight_control_method backlight_control[16];
+       struct lfp_brightness_level brightness_level[16];               /* 234+ */
+       struct lfp_brightness_level brightness_min_level[16];   /* 234+ */
+       u8 brightness_precision_bits[16];                                               /* 236+ */
 } __packed;
 
 /*