[PATCH 1/1] drm/i915: Add Backlight Control using DPCD for eDP connectors

Yetunde Adebisi
2015-09-30T14:36:17Z

This patch adds support for eDP backlight control using DPCD registers to
backlight hooks in intel_panel.

It checks for backlight control over AUX channel capability and sets up
function pointers to get and set the backlight brightness level if
supported.

Cc: Bob Paauwe <bob.j.paauwe@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Deepak M <m.deepak@intel.com>
Signed-off-by: Yetunde Adebisi <yetundex.adebisi@intel.com>
---
drivers/gpu/drm/i915/intel_dp.c | 185 +++++++++++++++++++++++++++++++++++++
drivers/gpu/drm/i915/intel_drv.h | 3 +
drivers/gpu/drm/i915/intel_panel.c | 5 +-
include/drm/drm_dp_helper.h | 6 ++
4 files changed, 198 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index fa1a524..fc4b896 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -6259,3 +6259,188 @@ void intel_dp_mst_resume(struct drm_device *dev)
}
}
}
+
+static uint8_t read_aux_backlight_mode_set_reg(struct intel_dp *intel_dp)
+{
+ uint8_t dpcd_buf = 0;
+
+ if (intel_dp_dpcd_read_wake(&intel_dp->aux,
+ DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+ &dpcd_buf, sizeof(dpcd_buf)) < 0)
+ DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+ DP_EDP_BACKLIGHT_MODE_SET_REGISTER);
+
+ return dpcd_buf;
+}
+
+static bool get_aux_backlight_enable(struct drm_dp_aux *aux)
+{
+ uint8_t read_val = 0;
+
+ if (intel_dp_dpcd_read_wake(aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ &read_val, sizeof(read_val)) < 0) {
+ DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+ DP_EDP_DISPLAY_CONTROL_REGISTER);
+ }
+ return read_val & DP_EDP_BACKLIGHT_ENABLE;
+}
+
+static void set_aux_backlight_enable(struct intel_dp *intel_dp, bool enable)
+{
+ uint8_t reg_val = 0;
+
+ if (intel_dp_dpcd_read_wake(&intel_dp->aux,
+ DP_EDP_DISPLAY_CONTROL_REGISTER,
+ &reg_val, sizeof(reg_val)) < 0) {
+ DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+ DP_EDP_DISPLAY_CONTROL_REGISTER);
+ return;
+ }
+ if (enable)
+ reg_val |= DP_EDP_BACKLIGHT_ENABLE;
+ else
+ reg_val &= ~(DP_EDP_BACKLIGHT_ENABLE);
+
+ if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_DISPLAY_CONTROL_REGISTER,
+ reg_val) < 0) {
+ DRM_DEBUG_KMS("Failed to %s aux backlight\n",
+ enable ? "enable" : "disable");
+ }
+}
+
+/**
+ * Read the current backlight value from DPCD register(s) based
+ * on if 8-bit(MSB) or 16-bit(MSB and LSB) values are supported
+ */
+static uint32_t intel_dp_aux_get_backlight(struct intel_connector *connector)
+{
+ struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
+ uint16_t read_val = 0;
+
+ if (intel_dp_dpcd_read_wake(&intel_dp->aux,
+ DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+ &read_val, sizeof(read_val)) < 0) {
+ DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+ DP_EDP_BACKLIGHT_BRIGHTNESS_MSB);
+ return 0;
+ }
+ if (intel_dp->aux_blc_use_lsb) {
+ uint8_t val_lsb = 0;
+
+ if (intel_dp_dpcd_read_wake(&intel_dp->aux,
+ DP_EDP_BACKLIGHT_BRIGHTNESS_LSB,
+ &val_lsb, sizeof(val_lsb)) < 0) {
+ DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n",
+ DP_EDP_BACKLIGHT_BRIGHTNESS_LSB);
+ return 0;
+ }
+ read_val = (read_val << 8 | val_lsb);
+ }
+
+ return read_val;
+}
+
+/**
+ * Sends the current backlight level over the aux channel, checking if its using
+ * 8-bit or 16 bit value (MSB and LSB)
+ */
+static void
+intel_dp_aux_set_backlight(struct intel_connector *connector, u32 level)
+{
+ struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
+ uint8_t vals[2] = { 0x0 };
+
+ vals[0] = level;
+ DRM_DEBUG_KMS("Level 0x%x\n", level);
+
+ /* Write the MSB and/or LSB */
+ if (intel_dp->aux_blc_use_lsb) {
+ vals[0] = (level & 0xFF00) >> 8;
+ vals[1] = (level & 0xFF);
+ if (drm_dp_dpcd_writeb(&intel_dp->aux,
+ DP_EDP_BACKLIGHT_BRIGHTNESS_LSB, vals[1]) < 0) {
+ DRM_DEBUG_KMS("Failed to write aux backlight level\n");
+ return;
+ }
+ }
+ if (drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+ vals[0]) < 0) {
+ DRM_DEBUG_KMS("Failed to write aux backlight level\n");
+ return;
+ }
+}
+
+static void intel_dp_aux_enable_backlight(struct intel_connector *connector)
+{
+ set_aux_backlight_enable(intel_attached_dp(&connector->base), true);
+}
+
+static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
+{
+ set_aux_backlight_enable(intel_attached_dp(&connector->base), false);
+}
+
+static int intel_dp_aux_setup_backlight(struct intel_connector *connector,
+ enum pipe pipe)
+{
+ struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
+ struct intel_panel *panel = &connector->panel;
+
+ if (!intel_dp_aux_display_control_capable(connector)) {
+ DRM_DEBUG_KMS("Backlight control over AUX not supported\n");
+ return -ENODEV;
+ }
+
+ if (intel_dp->aux_blc_use_lsb)
+ panel->backlight.max = 0xFFFF;
+ else
+ panel->backlight.max = 0xFF;
+
+ panel->backlight.min = 0;
+
+ panel->backlight.level = intel_dp_aux_get_backlight(connector);
+ panel->backlight.enabled = get_aux_backlight_enable(&intel_dp->aux);
+
+ return 0;
+}
+
+void intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
+{
+ struct intel_panel *panel = &intel_connector->panel;
+
+ panel->backlight.setup = intel_dp_aux_setup_backlight;
+ panel->backlight.enable = intel_dp_aux_enable_backlight;
+ panel->backlight.disable = intel_dp_aux_disable_backlight;
+ panel->backlight.set = intel_dp_aux_set_backlight;
+ panel->backlight.get = intel_dp_aux_get_backlight;
+}
+
+bool intel_dp_aux_display_control_capable(struct intel_connector *connector)
+{
+ struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
+ uint8_t dpcd_edp[2] = { 0x0 };
+
+ /* Check the eDP Display control capabilities registers to determine if
+ * the panel can support backlight control over the aux channel*/
+ if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_GENERAL_CAP_1,
+ dpcd_edp, sizeof(dpcd_edp)) < 0) {
+ DRM_DEBUG_KMS("Failed to read DPCD Display Control registers\n");
+ return false;
+ }
+ DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(dpcd_edp), dpcd_edp);
+
+ if (dpcd_edp[0] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAPABLE &&
+ (dpcd_edp[0] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAPABLE) &&
+ (dpcd_edp[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE) &&
+ ((read_aux_backlight_mode_set_reg(intel_dp) &
+ DP_EDP_BACKLIGHT_BRIGHTNESS_CTL_MODE_DPCD_MASK))) {
+
+ DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
+
+ if (dpcd_edp[1] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+ intel_dp->aux_blc_use_lsb = true;
+
+ return true;
+ }
+ return false;
+}
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 35a65ca..dacbc37 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -747,6 +747,7 @@ struct intel_dp {
unsigned long last_power_cycle;
unsigned long last_power_on;
unsigned long last_backlight_off;
+ bool aux_blc_use_lsb;

struct notifier_block edp_notifier;

@@ -1221,6 +1222,8 @@ void intel_edp_drrs_invalidate(struct drm_device *dev,
unsigned frontbuffer_bits);
void intel_edp_drrs_flush(struct drm_device *dev, unsigned frontbuffer_bits);
void hsw_dp_set_ddi_pll_sel(struct intel_crtc_state *pipe_config);
+bool intel_dp_aux_display_control_capable(struct intel_connector *connector);
+void intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector);

/* intel_dp_mst.c */
int intel_dp_mst_encoder_init(struct intel_digital_port *intel_dig_port, int conn_id);
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 9adb62b..04eff34 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1685,7 +1685,10 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
struct drm_device *dev = intel_connector->base.dev;
struct drm_i915_private *dev_priv = dev->dev_private;

- if (IS_BROXTON(dev)) {
+ if (intel_connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
+ intel_dp_aux_display_control_capable(intel_connector)) {
+ intel_dp_aux_init_backlight_funcs(intel_connector);
+ } else if (IS_BROXTON(dev)) {
panel->backlight.setup = bxt_setup_backlight;
panel->backlight.enable = bxt_enable_backlight;
panel->backlight.disable = bxt_disable_backlight;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 9ec4716..7367e1a 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -455,16 +455,22 @@
# define DP_EDP_14 0x03

#define DP_EDP_GENERAL_CAP_1 0x701
+#define DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAPABLE (1 << 0)
+#define DP_EDP_BACKLIGHT_AUX_ENABLE_CAPABLE (1 << 2)

#define DP_EDP_BACKLIGHT_ADJUSTMENT_CAP 0x702
+#define DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE (1 << 1)
+#define DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT (1 << 2)

#define DP_EDP_GENERAL_CAP_2 0x703

#define DP_EDP_GENERAL_CAP_3 0x704 /* eDP 1.4 */

#define DP_EDP_DISPLAY_CONTROL_REGISTER 0x720
+#define DP_EDP_BACKLIGHT_ENABLE (1 << 0)

#define DP_EDP_BACKLIGHT_MODE_SET_REGISTER 0x721
+#define DP_EDP_BACKLIGHT_BRIGHTNESS_CTL_MODE_DPCD_MASK 0x2

#define DP_EDP_BACKLIGHT_BRIGHTNESS_MSB 0x722
#define DP_EDP_BACKLIGHT_BRIGHTNESS_LSB 0x723
--
1.9.3