drm: Helper for lspcon in drm_dp_dual_mode

This patch adds lspcon support in dp_dual_mode helper.
lspcon is essentially a dp->hdmi dongle with dual personality.

LS mode: It works as a passive dongle, by level shifting DP++
signals to HDMI signals, in LS mode.
PCON mode: It works as a protocol converter active dongle
in pcon mode, by converting DP++ outputs to HDMI 2.0 outputs.

This patch adds support for lspcon detection and mode set
switch operations, as a dp dual mode dongle.

v2: Addressed review comments from Ville
- add adaptor id for lspcon devices (0x08), use it to identify lspcon
- change function names
  old: drm_lspcon_get_current_mode/drm_lspcon_change_mode
  new: drm_lspcon_get_mode/drm_lspcon_set_mode
- change drm_lspcon_get_mode type to int, to match
  drm_dp_dual_mode_get_tmds_output
- change 'err' to 'ret' to match the rest of the functions
- remove pointless typecasting during call to dual_mode_read
- fix the but while setting value of data, while writing lspcon mode
- fix indentation
- change mdelay(10) -> msleep(10)
- return ETIMEDOUT instead of EFAULT, when lspcon mode change times out
- Add an empty line to separate std regs macros and lspcon regs macros
  Indent bit definition

v3: Addressed review comments from Rodrigo
- change macro name from DP_DUAL_MODE_TYPE_LSPCON to
  DP_DUAL_MODE_TYPE_HAS_DPCD for better readability
- change macro name from DP_DUAL_MODE_LSPCON_MODE_PCON to
  DP_DUAL_MODE_LSPCON_MODE_PCON for better readability
- add comment for MCA specific offsets like 0x40 and 0x41
- remove DP_DUAL_MODE_REV_TYPE2 check while checking lspcon adapter id

v4: Addressed review comments from Ville
- Fixed indentation at few places
- s/current_mode/mode
- s/reqd_mode/mode
- remove unnecessary void* cast
- remove drm_edid.h from includes
- Add a comment for _HAS_DPCD
- Fix enum description, for lspcon_mode.

v5: Rebase
v6: Rebase
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1476720277-16298-1-git-send-email-shashank.sharma@intel.com

drivers/gpu/drm/drm_dp_dual_mode_helper.c

@@ -148,6 +148,14 @@ static bool is_type2_adaptor(uint8_t adaptor_id)
 			      DP_DUAL_MODE_REV_TYPE2);
 }
 
+bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
+	const uint8_t adaptor_id)
+{
+	return is_hdmi_adaptor(hdmi_id) &&
+		(adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
+		 DP_DUAL_MODE_TYPE_HAS_DPCD));
+}
+
 /**
  * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
  * @adapter: I2C adapter for the DDC bus
@@ -203,6 +211,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
 				    &adaptor_id, sizeof(adaptor_id));
 	if (ret == 0) {
+		if (is_lspcon_adaptor(hdmi_id, adaptor_id))
+			return DRM_DP_DUAL_MODE_LSPCON;
 		if (is_type2_adaptor(adaptor_id)) {
 			if (is_hdmi_adaptor(hdmi_id))
 				return DRM_DP_DUAL_MODE_TYPE2_HDMI;
@@ -364,3 +374,96 @@ const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
 	}
 }
 EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
+
+/**
+ * drm_lspcon_get_mode: Get LSPCON's current mode of operation by
+ * by reading offset (0x80, 0x41)
+ * @i2c_adapter: I2C-over-aux adapter
+ * @current_mode: out vaiable, current lspcon mode of operation
+ *
+ * Returns:
+ * 0 on success, sets the current_mode value to appropriate mode
+ * -error on failure
+ */
+int drm_lspcon_get_mode(struct i2c_adapter *adapter,
+			enum drm_lspcon_mode *mode)
+{
+	u8 data;
+	int ret = 0;
+
+	if (!mode) {
+		DRM_ERROR("NULL input\n");
+		return -EINVAL;
+	}
+
+	/* Read Status: i2c over aux */
+	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
+				    &data, sizeof(data));
+	if (ret < 0) {
+		DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
+		return -EFAULT;
+	}
+
+	if (data & DP_DUAL_MODE_LSPCON_MODE_PCON)
+		*mode = DRM_LSPCON_MODE_PCON;
+	else
+		*mode = DRM_LSPCON_MODE_LS;
+	return 0;
+}
+EXPORT_SYMBOL(drm_lspcon_get_mode);
+
+/**
+ * drm_lspcon_change_mode: Change LSPCON's mode of operation by
+ * by writing offset (0x80, 0x40)
+ * @i2c_adapter: I2C-over-aux adapter
+ * @reqd_mode: required mode of operation
+ *
+ * Returns:
+ * 0 on success, -error on failure/timeout
+ */
+int drm_lspcon_set_mode(struct i2c_adapter *adapter,
+			enum drm_lspcon_mode mode)
+{
+	u8 data = 0;
+	int ret;
+	int time_out = 200;
+	enum drm_lspcon_mode current_mode;
+
+	if (mode == DRM_LSPCON_MODE_PCON)
+		data = DP_DUAL_MODE_LSPCON_MODE_PCON;
+
+	/* Change mode */
+	ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
+				     &data, sizeof(data));
+	if (ret < 0) {
+		DRM_ERROR("LSPCON mode change failed\n");
+		return ret;
+	}
+
+	/*
+	 * Confirm mode change by reading the status bit.
+	 * Sometimes, it takes a while to change the mode,
+	 * so wait and retry until time out or done.
+	 */
+	do {
+		ret = drm_lspcon_get_mode(adapter, &current_mode);
+		if (ret) {
+			DRM_ERROR("can't confirm LSPCON mode change\n");
+			return ret;
+		} else {
+			if (current_mode != mode) {
+				msleep(10);
+				time_out -= 10;
+			} else {
+				DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
+						mode == DRM_LSPCON_MODE_LS ?
+						"LS" : "PCON");
+				return 0;
+			}
+		}
+	} while (time_out);
+
+	DRM_ERROR("LSPCON mode change timed out\n");
+	return -ETIMEDOUT;
+}
+EXPORT_SYMBOL(drm_lspcon_set_mode);

include/drm/drm_dp_dual_mode_helper.h

@@ -40,6 +40,8 @@
 #define  DP_DUAL_MODE_REV_TYPE2 0x00
 #define  DP_DUAL_MODE_TYPE_MASK 0xf0
 #define  DP_DUAL_MODE_TYPE_TYPE2 0xa0
+/* This field is marked reserved in dual mode spec, used in LSPCON */
+#define  DP_DUAL_MODE_TYPE_HAS_DPCD 0x08
 #define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
 #define  DP_DUAL_IEEE_OUI_LEN 3
 #define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
@@ -55,6 +57,11 @@
 #define  DP_DUAL_MODE_CEC_ENABLE 0x01
 #define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
 
+/* LSPCON specific registers, defined by MCA */
+#define DP_DUAL_MODE_LSPCON_MODE_CHANGE		0x40
+#define DP_DUAL_MODE_LSPCON_CURRENT_MODE		0x41
+#define  DP_DUAL_MODE_LSPCON_MODE_PCON			0x1
+
 struct i2c_adapter;
 
 ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
@@ -62,6 +69,19 @@ ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
 ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
 			       u8 offset, const void *buffer, size_t size);
 
+/**
+* enum drm_lspcon_mode
+* @lspcon_mode_ls: Level shifter mode of LSPCON
+*	which drives DP++ to HDMI 1.4 conversion.
+* @lspcon_mode_pcon: Protocol converter mode of LSPCON
+*	which drives DP++ to HDMI 2.0 active conversion.
+*/
+enum drm_lspcon_mode {
+	DRM_LSPCON_MODE_INVALID,
+	DRM_LSPCON_MODE_LS,
+	DRM_LSPCON_MODE_PCON,
+};
+
 /**
  * enum drm_dp_dual_mode_type - Type of the DP dual mode adaptor
  * @DRM_DP_DUAL_MODE_NONE: No DP dual mode adaptor
@@ -70,6 +90,7 @@ ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
  * @DRM_DP_DUAL_MODE_TYPE1_HDMI: Type 1 HDMI adaptor
  * @DRM_DP_DUAL_MODE_TYPE2_DVI: Type 2 DVI adaptor
  * @DRM_DP_DUAL_MODE_TYPE2_HDMI: Type 2 HDMI adaptor
+ * @DRM_DP_DUAL_MODE_TYPE2_LSPCON: Level shifter /protocol converter
  */
 enum drm_dp_dual_mode_type {
 	DRM_DP_DUAL_MODE_NONE,
@@ -78,6 +99,7 @@ enum drm_dp_dual_mode_type {
 	DRM_DP_DUAL_MODE_TYPE1_HDMI,
 	DRM_DP_DUAL_MODE_TYPE2_DVI,
 	DRM_DP_DUAL_MODE_TYPE2_HDMI,
+	DRM_DP_DUAL_MODE_LSPCON,
 };
 
 enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter);
@@ -89,4 +111,8 @@ int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
 				     struct i2c_adapter *adapter, bool enable);
 const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type);
 
+int drm_lspcon_get_mode(struct i2c_adapter *adapter,
+			enum drm_lspcon_mode *current_mode);
+int drm_lspcon_set_mode(struct i2c_adapter *adapter,
+			enum drm_lspcon_mode reqd_mode);
 #endif