drm/i915/sdvo: Fix GMBUSification

Besides a couple of bugs when writing more than a single byte along the
GMBUS, SDVO was completely failing whilst trying to use GMBUS, so use
bit banging instead.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

5 files changed, 339 insertions, 196 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 710d59e..0bb2553 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -132,10 +132,12 @@ struct drm_i915_fence_reg {
 };
 
 struct sdvo_device_mapping {
+	u8 initialized;
 	u8 dvo_port;
 	u8 slave_addr;
 	u8 dvo_wiring;
-	u8 initialized;
+	u8 i2c_pin;
+	u8 i2c_speed;
 	u8 ddc_pin;
 };
 
@@ -248,8 +250,8 @@ typedef struct drm_i915_private {
 
 	struct intel_gmbus {
 		struct i2c_adapter adapter;
-		struct i2c_adapter *force_bitbanging;
-		int pin;
+		struct i2c_adapter *force_bit;
+		u32 reg0;
 	} *gmbus;
 
 	struct pci_dev *bridge_dev;
@@ -1104,6 +1106,8 @@ extern int i915_restore_state(struct drm_device *dev);
 /* intel_i2c.c */
 extern int intel_setup_gmbus(struct drm_device *dev);
 extern void intel_teardown_gmbus(struct drm_device *dev);
+extern void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed);
+extern void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit);
 extern void intel_i2c_reset(struct drm_device *dev);
 
 /* intel_opregion.c */
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 42a7a5b..7e868d2 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -369,7 +369,16 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv,
 			p_mapping->slave_addr = p_child->slave_addr;
 			p_mapping->dvo_wiring = p_child->dvo_wiring;
 			p_mapping->ddc_pin = p_child->ddc_pin;
+			p_mapping->i2c_pin = p_child->i2c_pin;
+			p_mapping->i2c_speed = p_child->i2c_speed;
 			p_mapping->initialized = 1;
+			DRM_DEBUG_KMS("SDVO device: dvo=%x, addr=%x, wiring=%d, ddc_pin=%d, i2c_pin=%d, i2c_speed=%d\n",
+				      p_mapping->dvo_port,
+				      p_mapping->slave_addr,
+				      p_mapping->dvo_wiring,
+				      p_mapping->ddc_pin,
+				      p_mapping->i2c_pin,
+				      p_mapping->i2c_speed);
 		} else {
 			DRM_DEBUG_KMS("Maybe one SDVO port is shared by "
 					 "two SDVO device.\n");
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index 4c18514..e1a598f 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -197,7 +197,8 @@ struct bdb_general_features {
 struct child_device_config {
 	u16 handle;
 	u16 device_type;
-	u8  device_id[10]; /* See DEVICE_TYPE_* above */
+	u8  i2c_speed;
+	u8  rsvd[9];
 	u16 addin_offset;
 	u8  dvo_port; /* See Device_PORT_* above */
 	u8  i2c_pin;
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 6f4d1289..9192024 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -38,6 +38,12 @@
 
 #define I2C_RISEFALL_TIME 20
 
+static inline struct intel_gmbus *
+to_intel_gmbus(struct i2c_adapter *i2c)
+{
+	return container_of(i2c, struct intel_gmbus, adapter);
+}
+
 struct intel_gpio {
 	struct i2c_adapter adapter;
 	struct i2c_algo_bit_data algo;
@@ -71,10 +77,27 @@ static void intel_i2c_quirk_set(struct drm_i915_private *dev_priv, bool enable)
 	I915_WRITE(DSPCLK_GATE_D, val);
 }
 
+static u32 get_reserved(struct intel_gpio *gpio)
+{
+	struct drm_i915_private *dev_priv = gpio->dev_priv;
+	struct drm_device *dev = dev_priv->dev;
+	u32 reserved = 0;
+
+	/* On most chips, these bits must be preserved in software. */
+	if (!IS_I830(dev) && !IS_845G(dev))
+		reserved = I915_READ(gpio->reg) & (GPIO_DATA_PULLUP_DISABLE |
+						   GPIO_CLOCK_PULLUP_DISABLE);
+
+	return reserved;
+}
+
 static int get_clock(void *data)
 {
 	struct intel_gpio *gpio = data;
 	struct drm_i915_private *dev_priv = gpio->dev_priv;
+	u32 reserved = get_reserved(gpio);
+	I915_WRITE(gpio->reg, reserved | GPIO_CLOCK_DIR_MASK);
+	I915_WRITE(gpio->reg, reserved);
 	return (I915_READ(gpio->reg) & GPIO_CLOCK_VAL_IN) != 0;
 }
 
@@ -82,6 +105,9 @@ static int get_data(void *data)
 {
 	struct intel_gpio *gpio = data;
 	struct drm_i915_private *dev_priv = gpio->dev_priv;
+	u32 reserved = get_reserved(gpio);
+	I915_WRITE(gpio->reg, reserved | GPIO_DATA_DIR_MASK);
+	I915_WRITE(gpio->reg, reserved);
 	return (I915_READ(gpio->reg) & GPIO_DATA_VAL_IN) != 0;
 }
 
@@ -89,13 +115,8 @@ static void set_clock(void *data, int state_high)
 {
 	struct intel_gpio *gpio = data;
 	struct drm_i915_private *dev_priv = gpio->dev_priv;
-	struct drm_device *dev = dev_priv->dev;
-	u32 reserved = 0, clock_bits;
-
-	/* On most chips, these bits must be preserved in software. */
-	if (!IS_I830(dev) && !IS_845G(dev))
-		reserved = I915_READ(gpio->reg) & (GPIO_DATA_PULLUP_DISABLE |
-						   GPIO_CLOCK_PULLUP_DISABLE);
+	u32 reserved = get_reserved(gpio);
+	u32 clock_bits;
 
 	if (state_high)
 		clock_bits = GPIO_CLOCK_DIR_IN | GPIO_CLOCK_DIR_MASK;
@@ -111,13 +132,8 @@ static void set_data(void *data, int state_high)
 {
 	struct intel_gpio *gpio = data;
 	struct drm_i915_private *dev_priv = gpio->dev_priv;
-	struct drm_device *dev = dev_priv->dev;
-	u32 reserved = 0, data_bits;
-
-	/* On most chips, these bits must be preserved in software. */
-	if (!IS_I830(dev) && !IS_845G(dev))
-		reserved = I915_READ(gpio->reg) & (GPIO_DATA_PULLUP_DISABLE |
-						   GPIO_CLOCK_PULLUP_DISABLE);
+	u32 reserved = get_reserved(gpio);
+	u32 data_bits;
 
 	if (state_high)
 		data_bits = GPIO_DATA_DIR_IN | GPIO_DATA_DIR_MASK;
@@ -155,7 +171,7 @@ intel_gpio_create(struct drm_i915_private *dev_priv, u32 pin)
 		gpio->reg += PCH_GPIOA - GPIOA;
 	gpio->dev_priv = dev_priv;
 
-	snprintf(gpio->adapter.name, I2C_NAME_SIZE, "GPIO %d", pin);
+	snprintf(gpio->adapter.name, I2C_NAME_SIZE, "GPIO%c", "?BACDEF?"[pin]);
 	gpio->adapter.owner = THIS_MODULE;
 	gpio->adapter.algo_data	= &gpio->algo;
 	gpio->adapter.dev.parent = &dev_priv->dev->pdev->dev;
@@ -170,16 +186,6 @@ intel_gpio_create(struct drm_i915_private *dev_priv, u32 pin)
 	if (i2c_bit_add_bus(&gpio->adapter))
 		goto out_free;
 
-	intel_i2c_reset(dev_priv->dev);
-
-	/* JJJ:  raise SCL and SDA? */
-	intel_i2c_quirk_set(dev_priv, true);
-	set_data(gpio, 1);
-	udelay(I2C_RISEFALL_TIME);
-	set_clock(gpio, 1);
-	udelay(I2C_RISEFALL_TIME);
-	intel_i2c_quirk_set(dev_priv, false);
-
 	return &gpio->adapter;
 
 out_free:
@@ -188,17 +194,27 @@ out_free:
 }
 
 static int
-quirk_i2c_transfer(struct drm_i915_private *dev_priv,
-		   struct i2c_adapter *adapter,
-		   struct i2c_msg *msgs,
-		   int num)
+intel_i2c_quirk_xfer(struct drm_i915_private *dev_priv,
+		     struct i2c_adapter *adapter,
+		     struct i2c_msg *msgs,
+		     int num)
 {
+	struct intel_gpio *gpio = container_of(adapter,
+					       struct intel_gpio,
+					       adapter);
 	int ret;
 
 	intel_i2c_reset(dev_priv->dev);
 
 	intel_i2c_quirk_set(dev_priv, true);
-	ret = i2c_transfer(adapter, msgs, num);
+	set_data(gpio, 1);
+	set_clock(gpio, 1);
+	udelay(I2C_RISEFALL_TIME);
+
+	ret = adapter->algo->master_xfer(adapter, msgs, num);
+
+	set_data(gpio, 1);
+	set_clock(gpio, 1);
 	intel_i2c_quirk_set(dev_priv, false);
 
 	return ret;
@@ -213,21 +229,15 @@ gmbus_xfer(struct i2c_adapter *adapter,
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = adapter->algo_data;
-	int i, speed, reg_offset;
+	int i, reg_offset;
 
-	if (bus->force_bitbanging)
-		return quirk_i2c_transfer(dev_priv, bus->force_bitbanging, msgs, num);
+	if (bus->force_bit)
+		return intel_i2c_quirk_xfer(dev_priv,
+					    bus->force_bit, msgs, num);
 
 	reg_offset = HAS_PCH_SPLIT(dev_priv->dev) ? PCH_GMBUS0 - GMBUS0 : 0;
 
-	speed = GMBUS_RATE_100KHZ;
-	if (INTEL_INFO(dev_priv->dev)->gen > 4 || IS_G4X(dev_priv->dev)) {
-		if (bus->pin == GMBUS_PORT_DPB) /* SDVO only? */
-			speed = GMBUS_RATE_1MHZ;
-		else
-			speed = GMBUS_RATE_400KHZ;
-	}
-	I915_WRITE(GMBUS0 + reg_offset, speed | bus->pin);
+	I915_WRITE(GMBUS0 + reg_offset, bus->reg0);
 
 	for (i = 0; i < num; i++) {
 		u16 len = msgs[i].len;
@@ -239,6 +249,7 @@ gmbus_xfer(struct i2c_adapter *adapter,
 				   (len << GMBUS_BYTE_COUNT_SHIFT) |
 				   (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) |
 				   GMBUS_SLAVE_READ | GMBUS_SW_RDY);
+			POSTING_READ(GMBUS2+reg_offset);
 			do {
 				u32 val, loop = 0;
 
@@ -254,20 +265,35 @@ gmbus_xfer(struct i2c_adapter *adapter,
 				} while (--len && ++loop < 4);
 			} while (len);
 		} else {
-			u32 val = 0, loop = 0;
-
-			BUG_ON(msgs[i].len > 4);
+			u32 val, loop;
 
+			val = loop = 0;
 			do {
-				val |= *buf++ << (loop*8);
-			} while (--len && +loop < 4);
+				val |= *buf++ << (8 * loop);
+			} while (--len && ++loop < 4);
 
 			I915_WRITE(GMBUS3 + reg_offset, val);
 			I915_WRITE(GMBUS1 + reg_offset,
-				   (i + 1 == num ? GMBUS_CYCLE_STOP : GMBUS_CYCLE_WAIT ) |
+				   (i + 1 == num ? GMBUS_CYCLE_STOP : GMBUS_CYCLE_WAIT) |
 				   (msgs[i].len << GMBUS_BYTE_COUNT_SHIFT) |
 				   (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) |
 				   GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
+			POSTING_READ(GMBUS2+reg_offset);
+
+			while (len) {
+				if (wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_RDY), 50))
+					goto timeout;
+				if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
+					return 0;
+
+				val = loop = 0;
+				do {
+					val |= *buf++ << (8 * loop);
+				} while (--len && ++loop < 4);
+
+				I915_WRITE(GMBUS3 + reg_offset, val);
+				POSTING_READ(GMBUS2+reg_offset);
+			}
 		}
 
 		if (i + 1 < num && wait_for(I915_READ(GMBUS2 + reg_offset) & (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE), 50))
@@ -279,17 +305,25 @@ gmbus_xfer(struct i2c_adapter *adapter,
 	return num;
 
 timeout:
-	DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d\n", bus->pin);
+	DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d [%s]\n",
+		 bus->reg0 & 0xff, bus->adapter.name);
 	/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
-	bus->force_bitbanging = intel_gpio_create(dev_priv, bus->pin);
-	if (!bus->force_bitbanging)
+	bus->force_bit = intel_gpio_create(dev_priv, bus->reg0 & 0xff);
+	if (!bus->force_bit)
 		return -ENOMEM;
 
-	return quirk_i2c_transfer(dev_priv, bus->force_bitbanging, msgs, num);
+	return intel_i2c_quirk_xfer(dev_priv, bus->force_bit, msgs, num);
 }
 
 static u32 gmbus_func(struct i2c_adapter *adapter)
 {
+	struct intel_gmbus *bus = container_of(adapter,
+					       struct intel_gmbus,
+					       adapter);
+
+	if (bus->force_bit)
+		bus->force_bit->algo->functionality(bus->force_bit);
+
 	return (I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 		/* I2C_FUNC_10BIT_ADDR | */
 		I2C_FUNC_SMBUS_READ_BLOCK_DATA |
@@ -307,15 +341,15 @@ static const struct i2c_algorithm gmbus_algorithm = {
  */
 int intel_setup_gmbus(struct drm_device *dev)
 {
-	static const char *names[] = {
+	static const char *names[GMBUS_NUM_PORTS] = {
 		"disabled",
 		"ssc",
 		"vga",
 		"panel",
 		"dpc",
 		"dpb",
-		"dpd",
 		"reserved"
+		"dpd",
 	};
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret, i;
@@ -343,7 +377,8 @@ int intel_setup_gmbus(struct drm_device *dev)
 		if (ret)
 			goto err;
 
-		bus->pin = i;
+		/* By default use a conservative clock rate */
+		bus->reg0 = i | GMBUS_RATE_100KHZ;
 	}
 
 	intel_i2c_reset(dev_priv->dev);
@@ -360,6 +395,38 @@ err:
 	return ret;
 }
 
+void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed)
+{
+	struct intel_gmbus *bus = to_intel_gmbus(adapter);
+
+	/* speed:
+	 * 0x0 = 100 KHz
+	 * 0x1 = 50 KHz
+	 * 0x2 = 400 KHz
+	 * 0x3 = 1000 Khz
+	 */
+	bus->reg0 = (bus->reg0 & ~(0x3 << 8)) | (speed << 8);
+}
+
+void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit)
+{
+	struct intel_gmbus *bus = to_intel_gmbus(adapter);
+
+	if (force_bit) {
+		if (bus->force_bit == NULL) {
+			struct drm_i915_private *dev_priv = adapter->algo_data;
+			bus->force_bit = intel_gpio_create(dev_priv,
+							   bus->reg0 & 0xff);
+		}
+	} else {
+		if (bus->force_bit) {
+			i2c_del_adapter(bus->force_bit);
+			kfree(bus->force_bit);
+			bus->force_bit = NULL;
+		}
+	}
+}
+
 void intel_teardown_gmbus(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -370,9 +437,9 @@ void intel_teardown_gmbus(struct drm_device *dev)
 
 	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
-		if (bus->force_bitbanging) {
-			i2c_del_adapter(bus->force_bitbanging);
-			kfree(bus->force_bitbanging);
+		if (bus->force_bit) {
+			i2c_del_adapter(bus->force_bit);
+			kfree(bus->force_bit);
 		}
 		i2c_del_adapter(&bus->adapter);
 	}
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 7cd2d95..b684a40 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -68,6 +68,8 @@ struct intel_sdvo {
 	struct i2c_adapter *i2c;
 	u8 slave_addr;
 
+	struct i2c_adapter ddc;
+
 	/* Register for the SDVO device: SDVOB or SDVOC */
 	int sdvo_reg;
 
@@ -247,49 +249,29 @@ static void intel_sdvo_write_sdvox(struct intel_sdvo *intel_sdvo, u32 val)
 
 static bool intel_sdvo_read_byte(struct intel_sdvo *intel_sdvo, u8 addr, u8 *ch)
 {
-	u8 out_buf[2] = { addr, 0 };
-	u8 buf[2];
 	struct i2c_msg msgs[] = {
 		{
-			.addr = intel_sdvo->slave_addr >> 1,
+			.addr = intel_sdvo->slave_addr,
 			.flags = 0,
 			.len = 1,
-			.buf = out_buf,
+			.buf = &addr,
 		},
 		{
-			.addr = intel_sdvo->slave_addr >> 1,
+			.addr = intel_sdvo->slave_addr,
 			.flags = I2C_M_RD,
 			.len = 1,
-			.buf = buf,
+			.buf = ch,
 		}
 	};
 	int ret;
 
 	if ((ret = i2c_transfer(intel_sdvo->i2c, msgs, 2)) == 2)
-	{
-		*ch = buf[0];
 		return true;
-	}
 
 	DRM_DEBUG_KMS("i2c transfer returned %d\n", ret);
 	return false;
 }
 
-static bool intel_sdvo_write_byte(struct intel_sdvo *intel_sdvo, int addr, u8 ch)
-{
-	u8 out_buf[2] = { addr, ch };
-	struct i2c_msg msgs[] = {
-		{
-			.addr = intel_sdvo->slave_addr >> 1,
-			.flags = 0,
-			.len = 2,
-			.buf = out_buf,
-		}
-	};
-
-	return i2c_transfer(intel_sdvo->i2c, msgs, 1) == 1;
-}
-
 #define SDVO_CMD_NAME_ENTRY(cmd) {cmd, #cmd}
 /** Mapping of command numbers to names, for debug output */
 static const struct _sdvo_cmd_name {
@@ -434,32 +416,80 @@ static void intel_sdvo_debug_write(struct intel_sdvo *intel_sdvo, u8 cmd,
 	DRM_LOG_KMS("\n");
 }
 
+static const char *cmd_status_names[] = {
+	"Power on",
+	"Success",
+	"Not supported",
+	"Invalid arg",
+	"Pending",
+	"Target not specified",
+	"Scaling not supported"
+};
+
 static bool intel_sdvo_write_cmd(struct intel_sdvo *intel_sdvo, u8 cmd,
 				 const void *args, int args_len)
 {
-	int i;
+	u8 buf[args_len*2 + 2], status;
+	struct i2c_msg msgs[args_len + 3];
+	int i, ret;
 
 	intel_sdvo_debug_write(intel_sdvo, cmd, args, args_len);
 
 	for (i = 0; i < args_len; i++) {
-		if (!intel_sdvo_write_byte(intel_sdvo, SDVO_I2C_ARG_0 - i,
-					   ((u8*)args)[i]))
+		msgs[i].addr = intel_sdvo->slave_addr;
+		msgs[i].flags = 0;
+		msgs[i].len = 2;
+		msgs[i].buf = buf + 2 *i;
+		buf[2*i + 0] = SDVO_I2C_ARG_0 - i;
+		buf[2*i + 1] = ((u8*)args)[i];
+	}
+	msgs[i].addr = intel_sdvo->slave_addr;
+	msgs[i].flags = 0;
+	msgs[i].len = 2;
+	msgs[i].buf = buf + 2*i;
+	buf[2*i + 0] = SDVO_I2C_OPCODE;
+	buf[2*i + 1] = cmd;
+
+	/* the following two are to read the response */
+	status = SDVO_I2C_CMD_STATUS;
+	msgs[i+1].addr = intel_sdvo->slave_addr;
+	msgs[i+1].flags = 0;
+	msgs[i+1].len = 1;
+	msgs[i+1].buf = &status;
+
+	msgs[i+2].addr = intel_sdvo->slave_addr;
+	msgs[i+2].flags = I2C_M_RD;
+	msgs[i+2].len = 1;
+	msgs[i+2].buf = &status;
+
+	ret = i2c_transfer(intel_sdvo->i2c, msgs, i+3);
+	if (ret < 0) {
+		DRM_DEBUG_KMS("I2c transfer returned %d\n", ret);
+		return false;
+	}
+	if (ret != i+3) {
+		/* failure in I2C transfer */
+		DRM_DEBUG_KMS("I2c transfer returned %d/%d\n", ret, i+3);
+		return false;
+	}
+
+	i = 3;
+	while (status == SDVO_CMD_STATUS_PENDING && i--) {
+		if (!intel_sdvo_read_byte(intel_sdvo,
+					  SDVO_I2C_CMD_STATUS,
+					  &status))
 			return false;
 	}
+	if (status != SDVO_CMD_STATUS_SUCCESS) {
+		DRM_DEBUG_KMS("command returns response %s [%d]\n",
+			      status <= SDVO_CMD_STATUS_SCALING_NOT_SUPP ? cmd_status_names[status] : "???",
+			      status);
+		return false;
+	}
 
-	return intel_sdvo_write_byte(intel_sdvo, SDVO_I2C_OPCODE, cmd);
+	return true;
 }
 
-static const char *cmd_status_names[] = {
-	"Power on",
-	"Success",
-	"Not supported",
-	"Invalid arg",
-	"Pending",
-	"Target not specified",
-	"Scaling not supported"
-};
-
 static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
 				     void *response, int response_len)
 {
@@ -497,13 +527,9 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo,
 					  SDVO_I2C_RETURN_0 + i,
 					  &((u8 *)response)[i]))
 			goto log_fail;
-		DRM_LOG_KMS("%02X ", ((u8 *)response)[i]);
+		DRM_LOG_KMS(" %02X", ((u8 *)response)[i]);
 	}
-
-	for (; i < 8; i++)
-		DRM_LOG_KMS("   ");
 	DRM_LOG_KMS("\n");
-
 	return true;
 
 log_fail:
@@ -521,75 +547,17 @@ static int intel_sdvo_get_pixel_multiplier(struct drm_display_mode *mode)
 		return 4;
 }
 
-/**
- * Try to read the response after issuie the DDC switch command. But it
- * is noted that we must do the action of reading response and issuing DDC
- * switch command in one I2C transaction. Otherwise when we try to start
- * another I2C transaction after issuing the DDC bus switch, it will be
- * switched to the internal SDVO register.
- */
-static int intel_sdvo_set_control_bus_switch(struct intel_sdvo *intel_sdvo,
-					     u8 target)
+static bool intel_sdvo_set_control_bus_switch(struct intel_sdvo *intel_sdvo,
+					      u8 ddc_bus)
 {
-	u8 out_buf[2], cmd_buf[2], ret_value[2], ret;
-	struct i2c_msg msgs[] = {
-		{
-			.addr = intel_sdvo->slave_addr >> 1,
-			.flags = 0,
-			.len = 2,
-			.buf = out_buf,
-		},
-		/* the following two are to read the response */
-		{
-			.addr = intel_sdvo->slave_addr >> 1,
-			.flags = 0,
-			.len = 1,
-			.buf = cmd_buf,
-		},
-		{
-			.addr = intel_sdvo->slave_addr >> 1,
-			.flags = I2C_M_RD,
-			.len = 1,
-			.buf = ret_value,
-		},
-	};
-
-	intel_sdvo_debug_write(intel_sdvo, SDVO_CMD_SET_CONTROL_BUS_SWITCH,
-			       &target, 1);
-	/* write the DDC switch command argument */
-	if (!intel_sdvo_write_byte(intel_sdvo, SDVO_I2C_ARG_0, target))
-		return -EIO;
-
-	out_buf[0] = SDVO_I2C_OPCODE;
-	out_buf[1] = SDVO_CMD_SET_CONTROL_BUS_SWITCH;
-	cmd_buf[0] = SDVO_I2C_CMD_STATUS;
-	cmd_buf[1] = 0;
-	ret_value[0] = 0;
-	ret_value[1] = 0;
-
-	ret = i2c_transfer(intel_sdvo->i2c, msgs, 3);
-	if (ret < 0)
-		return ret;
-	if (ret != 3) {
-		/* failure in I2C transfer */
-		DRM_DEBUG_KMS("I2c transfer returned %d\n", ret);
-		return -EIO;
-	}
-	if (ret_value[0] != SDVO_CMD_STATUS_SUCCESS) {
-		DRM_DEBUG_KMS("DDC switch command returns response %d\n",
-			      ret_value[0]);
-		return -EIO;
-	}
-
-	return 0;
+	return intel_sdvo_write_cmd(intel_sdvo,
+				    SDVO_CMD_SET_CONTROL_BUS_SWITCH,
+				    &ddc_bus, 1);
 }
 
 static bool intel_sdvo_set_value(struct intel_sdvo *intel_sdvo, u8 cmd, const void *data, int len)
 {
-	if (!intel_sdvo_write_cmd(intel_sdvo, cmd, data, len))
-		return false;
-
-	return intel_sdvo_read_response(intel_sdvo, NULL, 0);
+	return intel_sdvo_write_cmd(intel_sdvo, cmd, data, len);
 }
 
 static bool
@@ -1272,7 +1240,38 @@ static int intel_sdvo_mode_valid(struct drm_connector *connector,
 
 static bool intel_sdvo_get_capabilities(struct intel_sdvo *intel_sdvo, struct intel_sdvo_caps *caps)
 {
-	return intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_DEVICE_CAPS, caps, sizeof(*caps));
+	if (!intel_sdvo_get_value(intel_sdvo,
+				  SDVO_CMD_GET_DEVICE_CAPS,
+				  caps, sizeof(*caps)))
+		return false;
+
+	DRM_DEBUG_KMS("SDVO capabilities:\n"
+		      "  vendor_id: %d\n"
+		      "  device_id: %d\n"
+		      "  device_rev_id: %d\n"
+		      "  sdvo_version_major: %d\n"
+		      "  sdvo_version_minor: %d\n"
+		      "  sdvo_inputs_mask: %d\n"
+		      "  smooth_scaling: %d\n"
+		      "  sharp_scaling: %d\n"
+		      "  up_scaling: %d\n"
+		      "  down_scaling: %d\n"
+		      "  stall_support: %d\n"
+		      "  output_flags: %d\n",
+		      caps->vendor_id,
+		      caps->device_id,
+		      caps->device_rev_id,
+		      caps->sdvo_version_major,
+		      caps->sdvo_version_minor,
+		      caps->sdvo_inputs_mask,
+		      caps->smooth_scaling,
+		      caps->sharp_scaling,
+		      caps->up_scaling,
+		      caps->down_scaling,
+		      caps->stall_support,
+		      caps->output_flags);
+
+	return true;
 }
 
 /* No use! */
@@ -1377,16 +1376,10 @@ intel_sdvo_multifunc_encoder(struct intel_sdvo *intel_sdvo)
 }
 
 static struct edid *
-intel_sdvo_get_edid(struct drm_connector *connector, int ddc)
+intel_sdvo_get_edid(struct drm_connector *connector)
 {
-	struct intel_sdvo *intel_sdvo = intel_attached_sdvo(connector);
-	int ret;
-
-	ret = intel_sdvo_set_control_bus_switch(intel_sdvo, ddc);
-	if (ret)
-		return NULL;
-
-	return drm_get_edid(connector, intel_sdvo->i2c);
+	struct intel_sdvo *sdvo = intel_attached_sdvo(connector);
+	return drm_get_edid(connector, &sdvo->ddc);
 }
 
 static struct drm_connector *
@@ -1447,26 +1440,27 @@ intel_sdvo_hdmi_sink_detect(struct drm_connector *connector)
 	enum drm_connector_status status;
 	struct edid *edid;
 
-	edid = intel_sdvo_get_edid(connector, intel_sdvo->ddc_bus);
+	edid = intel_sdvo_get_edid(connector);
 
 	if (edid == NULL && intel_sdvo_multifunc_encoder(intel_sdvo)) {
-		u8 ddc;
+		u8 ddc, saved_ddc = intel_sdvo->ddc_bus;
 
 		/*
 		 * Don't use the 1 as the argument of DDC bus switch to get
 		 * the EDID. It is used for SDVO SPD ROM.
 		 */
 		for (ddc = intel_sdvo->ddc_bus >> 1; ddc > 1; ddc >>= 1) {
-			edid = intel_sdvo_get_edid(connector, ddc);
-			if (edid) {
-				/*
-				 * If we found the EDID on the other bus,
-				 * assume that is the correct DDC bus.
-				 */
-				intel_sdvo->ddc_bus = ddc;
+			intel_sdvo->ddc_bus = ddc;
+			edid = intel_sdvo_get_edid(connector);
+			if (edid)
 				break;
-			}
 		}
+		/*
+		 * If we found the EDID on the other bus,
+		 * assume that is the correct DDC bus.
+		 */
+		if (edid == NULL)
+			intel_sdvo->ddc_bus = saved_ddc;
 	}
 
 	/*
@@ -1499,7 +1493,7 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
 	enum drm_connector_status ret;
 
 	if (!intel_sdvo_write_cmd(intel_sdvo,
-			     SDVO_CMD_GET_ATTACHED_DISPLAYS, NULL, 0))
+				  SDVO_CMD_GET_ATTACHED_DISPLAYS, NULL, 0))
 		return connector_status_unknown;
 	if (intel_sdvo->is_tv) {
 		/* add 30ms delay when the output type is SDVO-TV */
@@ -1508,7 +1502,9 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
 	if (!intel_sdvo_read_response(intel_sdvo, &response, 2))
 		return connector_status_unknown;
 
-	DRM_DEBUG_KMS("SDVO response %d %d\n", response & 0xff, response >> 8);
+	DRM_DEBUG_KMS("SDVO response %d %d [%x]\n",
+		      response & 0xff, response >> 8,
+		      intel_sdvo_connector->output_flag);
 
 	if (response == 0)
 		return connector_status_disconnected;
@@ -1541,11 +1537,10 @@ intel_sdvo_detect(struct drm_connector *connector, bool force)
 
 static void intel_sdvo_get_ddc_modes(struct drm_connector *connector)
 {
-	struct intel_sdvo *intel_sdvo = intel_attached_sdvo(connector);
 	struct edid *edid;
 
 	/* set the bus switch and get the modes */
-	edid = intel_sdvo_get_edid(connector, intel_sdvo->ddc_bus);
+	edid = intel_sdvo_get_edid(connector);
 
 	/*
 	 * Mac mini hack.  On this device, the DVI-I connector shares one DDC
@@ -1647,7 +1642,8 @@ static void intel_sdvo_get_tv_modes(struct drm_connector *connector)
 		return;
 
 	BUILD_BUG_ON(sizeof(tv_res) != 3);
-	if (!intel_sdvo_write_cmd(intel_sdvo, SDVO_CMD_GET_SDTV_RESOLUTION_SUPPORT,
+	if (!intel_sdvo_write_cmd(intel_sdvo,
+				  SDVO_CMD_GET_SDTV_RESOLUTION_SUPPORT,
 				  &tv_res, sizeof(tv_res)))
 		return;
 	if (!intel_sdvo_read_response(intel_sdvo, &reply, 3))
@@ -1924,6 +1920,7 @@ static void intel_sdvo_enc_destroy(struct drm_encoder *encoder)
 		drm_mode_destroy(encoder->dev,
 				 intel_sdvo->sdvo_lvds_fixed_mode);
 
+	i2c_del_adapter(&intel_sdvo->ddc);
 	intel_encoder_destroy(encoder);
 }
 
@@ -1991,6 +1988,30 @@ intel_sdvo_select_ddc_bus(struct drm_i915_private *dev_priv,
 		intel_sdvo_guess_ddc_bus(sdvo);
 }
 
+static void
+intel_sdvo_select_i2c_bus(struct drm_i915_private *dev_priv,
+			  struct intel_sdvo *sdvo, u32 reg)
+{
+	struct sdvo_device_mapping *mapping;
+	u8 pin, speed;
+
+	if (IS_SDVOB(reg))
+		mapping = &dev_priv->sdvo_mappings[0];
+	else
+		mapping = &dev_priv->sdvo_mappings[1];
+
+	pin = GMBUS_PORT_DPB;
+	speed = GMBUS_RATE_1MHZ >> 8;
+	if (mapping->initialized) {
+		pin = mapping->i2c_pin;
+		speed = mapping->i2c_speed;
+	}
+
+	sdvo->i2c = &dev_priv->gmbus[pin].adapter;
+	intel_gmbus_set_speed(sdvo->i2c, speed);
+	intel_gmbus_force_bit(sdvo->i2c, true);
+}
+
 static bool
 intel_sdvo_get_digital_encoding_mode(struct intel_sdvo *intel_sdvo, int device)
 {
@@ -2504,7 +2525,43 @@ static bool intel_sdvo_create_enhance_property(struct intel_sdvo *intel_sdvo,
 		return intel_sdvo_create_enhance_property_lvds(intel_sdvo, intel_sdvo_connector, enhancements.reply);
 	else
 		return true;
+}
+
+static int intel_sdvo_ddc_proxy_xfer(struct i2c_adapter *adapter,
+				     struct i2c_msg *msgs,
+				     int num)
+{
+	struct intel_sdvo *sdvo = adapter->algo_data;
 
+	if (!intel_sdvo_set_control_bus_switch(sdvo, sdvo->ddc_bus))
+		return -EIO;
+
+	return sdvo->i2c->algo->master_xfer(sdvo->i2c, msgs, num);
+}
+
+static u32 intel_sdvo_ddc_proxy_func(struct i2c_adapter *adapter)
+{
+	struct intel_sdvo *sdvo = adapter->algo_data;
+	return sdvo->i2c->algo->functionality(sdvo->i2c);
+}
+
+static const struct i2c_algorithm intel_sdvo_ddc_proxy = {
+	.master_xfer	= intel_sdvo_ddc_proxy_xfer,
+	.functionality	= intel_sdvo_ddc_proxy_func
+};
+
+static bool
+intel_sdvo_init_ddc_proxy(struct intel_sdvo *sdvo,
+			  struct drm_device *dev)
+{
+	sdvo->ddc.owner = THIS_MODULE;
+	sdvo->ddc.class = I2C_CLASS_DDC;
+	snprintf(sdvo->ddc.name, I2C_NAME_SIZE, "SDVO DDC proxy");
+	sdvo->ddc.dev.parent = &dev->pdev->dev;
+	sdvo->ddc.algo_data = sdvo;
+	sdvo->ddc.algo = &intel_sdvo_ddc_proxy;
+
+	return i2c_add_adapter(&sdvo->ddc) == 0;
 }
 
 bool intel_sdvo_init(struct drm_device *dev, int sdvo_reg)
@@ -2518,6 +2575,11 @@ bool intel_sdvo_init(struct drm_device *dev, int sdvo_reg)
 	if (!intel_sdvo)
 		return false;
 
+	if (!intel_sdvo_init_ddc_proxy(intel_sdvo, dev)) {
+		kfree(intel_sdvo);
+		return false;
+	}
+
 	intel_sdvo->sdvo_reg = sdvo_reg;
 
 	intel_encoder = &intel_sdvo->base;
@@ -2525,9 +2587,8 @@ bool intel_sdvo_init(struct drm_device *dev, int sdvo_reg)
 	/* encoder type will be decided later */
 	drm_encoder_init(dev, &intel_encoder->base, &intel_sdvo_enc_funcs, 0);
 
-	intel_sdvo->i2c = &dev_priv->gmbus[GMBUS_PORT_DPB].adapter;
-
-	intel_sdvo->slave_addr = intel_sdvo_get_slave_addr(dev, sdvo_reg);
+	intel_sdvo->slave_addr = intel_sdvo_get_slave_addr(dev, sdvo_reg) >> 1;
+	intel_sdvo_select_i2c_bus(dev_priv, intel_sdvo, sdvo_reg);
 
 	/* Read the regs to test if we can talk to the device */
 	for (i = 0; i < 0x40; i++) {
@@ -2589,6 +2650,7 @@ bool intel_sdvo_init(struct drm_device *dev, int sdvo_reg)
 
 err:
 	drm_encoder_cleanup(&intel_encoder->base);
+	i2c_del_adapter(&intel_sdvo->ddc);
 	kfree(intel_sdvo);
 
 	return false;