google/trogdor: Add backlight support for Parade ps8640

Add backlight support in ps8640 through the AUX channel using eDP
DPCD registers.

BUG=b:202966352
BRANCH=trogdor
TEST=verified firmware screen works on homestar rev4

Change-Id: Ief1bf56c89c8215427dcbddfc67e8bcd4c3607d2
Signed-off-by: xuxinxiong <xuxinxiong@huaqin.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58624
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/dp_aux.h

@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _DP_AUX_H_
+#define _DP_AUX_H_
+
+#include <types.h>
+
+enum {
+	EDID_LENGTH         = 128,
+	EDID_I2C_ADDR       = 0x50,
+	EDID_EXTENSION_FLAG = 0x7e,
+};
+
+enum i2c_over_aux {
+	I2C_OVER_AUX_WRITE_MOT_0 = 0x0,
+	I2C_OVER_AUX_READ_MOT_0 = 0x1,
+	I2C_OVER_AUX_WRITE_STATUS_UPDATE_0 = 0x2,
+	I2C_OVER_AUX_WRITE_MOT_1 = 0x4,
+	I2C_OVER_AUX_READ_MOT_1 = 0x5,
+	I2C_OVER_AUX_WRITE_STATUS_UPDATE_1 = 0x6,
+	NATIVE_AUX_WRITE = 0x8,
+	NATIVE_AUX_READ = 0x9,
+};
+
+enum aux_request {
+	DPCD_READ,
+	DPCD_WRITE,
+	I2C_RAW_READ,
+	I2C_RAW_WRITE,
+	I2C_RAW_READ_AND_STOP,
+	I2C_RAW_WRITE_AND_STOP,
+};
+
+/* Backlight configuration */
+#define DP_BACKLIGHT_MODE_SET			0x721
+#define DP_BACKLIGHT_CONTROL_MODE_MASK		0x3
+#define DP_BACKLIGHT_CONTROL_MODE_DPCD		0x2
+#define DP_DISPLAY_CONTROL_REGISTER		0x720
+#define DP_BACKLIGHT_ENABLE			0x1
+#define DP_BACKLIGHT_BRIGHTNESS_MSB		0x722
+
+#define DP_AUX_MAX_PAYLOAD_BYTES	16
+
+
+bool dp_aux_request_is_write(enum aux_request request);
+enum i2c_over_aux dp_get_aux_cmd(enum aux_request request, uint32_t remaining_after_this);
+
+#endif