[Intel-gfx] [PATCH v5 6/9] drm/i915: Support dynamic backlight via DPCD register

[Puthikorn Voravootivat]

This patch enables dynamic backlight by default 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 <put...@chromium.org>
---
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 39 ++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c 
b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
index 5ef3ade7c40e..7d323af96636 100644
--- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -97,10 +97,27 @@ 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 new_dpcd_buf = 0;
        uint8_t edp_backlight_mode = 0;
 
        if (drm_dp_dpcd_readb(&intel_dp->aux,
@@ -110,18 +127,15 @@ 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 */
@@ -130,6 +144,19 @@ static void intel_dp_aux_enable_backlight(struct 
intel_connector *connector)
                break;
        }
 
+       if (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");
+       }
+
+       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);
 }
 
-- 
2.13.0.rc1.294.g07d810a77f-goog

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