[PATCH 2/3] drm/i915: Add Backlight Control using DPCD for eDP connectors (v7)

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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.

v2: Moved backlight functions from intel_dp.c into a new file
intel_dp_aux_backlight.c. Also moved reading of eDP display control
registers to intel_dp_get_dpcd

v3: Correct some formatting mistakes

v4: Updated to use AUX backlight control if PWM control is not possible
	(Jani)
v5: Moved call to initialize backlight registers to dp_aux_setup_backlight
v6: Check DP_EDP_BACKLIGHT_PIN_ENABLE_CAP is disabled before setting up AUX
backlight control. To fix BLM_PWM_ENABLE igt test warnings on bdw_ultra
v7: Add enable_dpcd_backlight module parameter.

This patch depends on http://patchwork.freedesktop.org/patch/64253/

Cc: Bob Paauwe <bob.j.paauwe@xxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Acked-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Signed-off-by: Yetunde Adebisi <yetundex.adebisi@xxxxxxxxx>
---
 drivers/gpu/drm/i915/Makefile                 |   1 +
 drivers/gpu/drm/i915/i915_params.c            |   5 +
 drivers/gpu/drm/i915/i915_params.h            |   1 +
 drivers/gpu/drm/i915/intel_dp.c               |  17 ++-
 drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 170 ++++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_drv.h              |   6 +
 drivers/gpu/drm/i915/intel_panel.c            |   5 +
 7 files changed, 199 insertions(+), 6 deletions(-)
 create mode 100644 drivers/gpu/drm/i915/intel_dp_aux_backlight.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 0851de07..41250cc 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -77,6 +77,7 @@ i915-y += dvo_ch7017.o \
 	  dvo_tfp410.o \
 	  intel_crt.o \
 	  intel_ddi.o \
+	  intel_dp_aux_backlight.o \
 	  intel_dp_link_training.o \
 	  intel_dp_mst.o \
 	  intel_dp.o \
diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 278c9c4..b10317e 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -56,6 +56,7 @@ struct i915_params i915 __read_mostly = {
 	.edp_vswing = 0,
 	.enable_guc_submission = false,
 	.guc_log_level = -1,
+	.enable_dpcd_backlight = false,
 };
 
 module_param_named(modeset, i915.modeset, int, 0400);
@@ -201,3 +202,7 @@ MODULE_PARM_DESC(enable_guc_submission, "Enable GuC submission (default:false)")
 module_param_named(guc_log_level, i915.guc_log_level, int, 0400);
 MODULE_PARM_DESC(guc_log_level,
 	"GuC firmware logging level (-1:disabled (default), 0-3:enabled)");
+
+module_param_named(enable_dpcd_backlight, i915.enable_dpcd_backlight, bool, 0600);
+MODULE_PARM_DESC(enable_dpcd_backlight,
+	"Enable support for DPCD backlight control (default:false)");
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index bd5026b..a40b8d9 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -59,6 +59,7 @@ struct i915_params {
 	bool enable_guc_submission;
 	bool verbose_state_checks;
 	bool nuclear_pageflip;
+	bool enable_dpcd_backlight;
 };
 
 extern struct i915_params i915 __read_mostly;
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 94b4a5b..9ccc581 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3180,7 +3180,7 @@ static void chv_dp_post_pll_disable(struct intel_encoder *encoder)
  * Sinks are *supposed* to come up within 1ms from an off state, but we're also
  * supposed to retry 3 times per the spec.
  */
-static ssize_t
+ssize_t
 intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
 			void *buffer, size_t size)
 {
@@ -3847,7 +3847,6 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
 	struct drm_device *dev = dig_port->base.base.dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	uint8_t rev;
 
 	if (intel_dp_dpcd_read_wake(&intel_dp->aux, 0x000, intel_dp->dpcd,
 				    sizeof(intel_dp->dpcd)) < 0)
@@ -3883,6 +3882,15 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 			DRM_DEBUG_KMS("PSR2 %s on sink",
 				dev_priv->psr.psr2_support ? "supported" : "not supported");
 		}
+
+		/* Read the eDP Display control capabilities registers */
+		memset(intel_dp->edp_dpcd, 0, sizeof(intel_dp->edp_dpcd));
+		if ((intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
+				(intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_DPCD_REV,
+						intel_dp->edp_dpcd, sizeof(intel_dp->edp_dpcd)) ==
+								sizeof(intel_dp->edp_dpcd)))
+			DRM_DEBUG_KMS("EDP DPCD : %*ph\n", (int) sizeof(intel_dp->edp_dpcd),
+					intel_dp->edp_dpcd);
 	}
 
 	DRM_DEBUG_KMS("Display Port TPS3 support: source %s, sink %s\n",
@@ -3890,10 +3898,7 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
 		      yesno(drm_dp_tps3_supported(intel_dp->dpcd)));
 
 	/* Intermediate frequency support */
-	if (is_edp(intel_dp) &&
-	    (intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] &	DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
-	    (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_DPCD_REV, &rev, 1) == 1) &&
-	    (rev >= 0x03)) { /* eDp v1.4 or higher */
+	if (is_edp(intel_dp) && (intel_dp->edp_dpcd[0] >= 0x03)) { /* eDp v1.4 or higher */
 		__le16 sink_rates[DP_MAX_SUPPORTED_RATES];
 		int i;
 
diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
new file mode 100644
index 0000000..a5361d6
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
@@ -0,0 +1,170 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#include "intel_drv.h"
+
+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 = enc_to_intel_dp(&connector->encoder->base);
+	uint8_t read_val[2] = { 0x0 };
+	uint16_t level = 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;
+	}
+	level = read_val[0];
+	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+		level = (read_val[0] << 8 | read_val[1]);
+
+	return level;
+}
+
+/*
+ * 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 = enc_to_intel_dp(&connector->encoder->base);
+	uint8_t vals[2] = { 0x0 };
+
+	vals[0] = level;
+
+	/* Write the MSB and/or LSB */
+	 if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT) {
+		vals[0] = (level & 0xFF00) >> 8;
+		vals[1] = (level & 0xFF);
+	}
+	if (drm_dp_dpcd_write(&intel_dp->aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB,
+			vals, sizeof(vals)) < 0) {
+		DRM_DEBUG_KMS("Failed to write aux backlight level\n");
+		return;
+	}
+}
+
+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;
+
+	set_aux_backlight_enable(intel_dp, true);
+
+	if ((intel_dp_dpcd_read_wake(&intel_dp->aux,
+			DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf, 1) == 1) &&
+			((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) ==
+					DP_EDP_BACKLIGHT_CONTROL_MODE_PRESET))
+		drm_dp_dpcd_writeb(&intel_dp->aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
+				(dpcd_buf | DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD));
+}
+
+static void intel_dp_aux_disable_backlight(struct intel_connector *connector)
+{
+	set_aux_backlight_enable(enc_to_intel_dp(&connector->encoder->base), false);
+}
+
+static int intel_dp_aux_setup_backlight(struct intel_connector *connector,
+			enum pipe pipe)
+{
+	struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
+	struct intel_panel *panel = &connector->panel;
+
+	intel_dp_aux_enable_backlight(connector);
+
+	if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
+		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 = panel->backlight.level != 0;
+
+	return 0;
+}
+
+static bool
+intel_dp_aux_display_control_capable(struct intel_connector *connector)
+{
+	struct intel_dp *intel_dp = enc_to_intel_dp(&connector->encoder->base);
+
+	/* Check the  eDP Display control capabilities registers to determine if
+	 * the panel can support backlight control over the aux channel
+	 */
+	if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP &&
+			(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) &&
+			!((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP) ||
+					(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP))) {
+
+		DRM_DEBUG_KMS("AUX Backlight Control Supported!\n");
+		return true;
+	}
+	return false;
+}
+
+int intel_dp_aux_init_backlight_funcs(struct intel_connector *intel_connector)
+{
+	struct intel_panel *panel = &intel_connector->panel;
+
+	if (!intel_dp_aux_display_control_capable(intel_connector))
+		return -ENODEV;
+
+	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;
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index cd0b4ea..6dd24c4 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -816,6 +816,7 @@ struct intel_dp {
 	uint8_t dpcd[DP_RECEIVER_CAP_SIZE];
 	uint8_t psr_dpcd[EDP_PSR_RECEIVER_CAP_SIZE];
 	uint8_t downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
+	uint8_t edp_dpcd[EDP_DISPLAY_CTL_CAP_SIZE];
 	/* sink rates as reported by DP_SUPPORTED_LINK_RATES */
 	uint8_t num_sink_rates;
 	int sink_rates[DP_MAX_SUPPORTED_RATES];
@@ -1336,6 +1337,11 @@ void intel_dp_compute_rate(struct intel_dp *intel_dp, int port_clock,
 bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
 bool
 intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE]);
+ssize_t intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
+		void *buffer, size_t size);
+
+/* intel_dp_aux_backlight.c */
+int 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 0fe059b..68fb3bd 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -1718,6 +1718,11 @@ intel_panel_init_backlight_funcs(struct intel_panel *panel)
 		container_of(panel, struct intel_connector, panel);
 	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
 
+	if (i915.enable_dpcd_backlight &&
+			(connector->base.connector_type == DRM_MODE_CONNECTOR_eDP &&
+					intel_dp_aux_init_backlight_funcs(connector) == 0))
+		return;
+
 	if (IS_BROXTON(dev_priv)) {
 		panel->backlight.setup = bxt_setup_backlight;
 		panel->backlight.enable = bxt_enable_backlight;
-- 
1.9.3

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