drivers/gpu/drm/i915/intel_i2c.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (c) 2006 Dave Airlie <airlied@linux.ie>
  * Copyright © 2006-2008,2010 Intel Corporation
  *   Jesse Barnes <jesse.barnes@intel.com>
  *
  * 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.
  *
  * Authors:
  *	Eric Anholt <eric@anholt.net>
  *	Chris Wilson <chris@chris-wilson.co.uk>
  */
 #include <linux/i2c.h>
 #include <linux/i2c-algo-bit.h>
 #include <linux/export.h>
 #include <drm/drmP.h>
 #include "intel_drv.h"
 #include <drm/i915_drm.h>
 #include "i915_drv.h"

 struct gmbus_port {
 	const char *name;
 	int reg;
 };

 static const struct gmbus_port gmbus_ports[] = {
 	{ "ssc", GPIOB },
 	{ "vga", GPIOA },
 	{ "panel", GPIOC },
 	{ "dpc", GPIOD },
 	{ "dpb", GPIOE },
 	{ "dpd", GPIOF },
 };

 /* Intel GPIO access functions */

 #define I2C_RISEFALL_TIME 10

 static inline struct intel_gmbus *
 to_intel_gmbus(struct i2c_adapter *i2c)
 {
 	return container_of(i2c, struct intel_gmbus, adapter);
 }

 void
 intel_i2c_reset(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	I915_WRITE(dev_priv->gpio_mmio_base + GMBUS0, 0);
 }

 static void intel_i2c_quirk_set(struct drm_i915_private *dev_priv, bool enable)
 {
 	u32 val;

 	/* When using bit bashing for I2C, this bit needs to be set to 1 */
 	if (!IS_PINEVIEW(dev_priv->dev))
 		return;

 	val = I915_READ(DSPCLK_GATE_D);
 	if (enable)
 		val |= DPCUNIT_CLOCK_GATE_DISABLE;
 	else
 		val &= ~DPCUNIT_CLOCK_GATE_DISABLE;
 	I915_WRITE(DSPCLK_GATE_D, val);
 }

 static u32 get_reserved(struct intel_gmbus *bus)
 {
 	struct drm_i915_private *dev_priv = bus->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_NOTRACE(bus->gpio_reg) &
 					     (GPIO_DATA_PULLUP_DISABLE |
 					      GPIO_CLOCK_PULLUP_DISABLE);

 	return reserved;
 }

 static int get_clock(void *data)
 {
 	struct intel_gmbus *bus = data;
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	u32 reserved = get_reserved(bus);
 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved | GPIO_CLOCK_DIR_MASK);
 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
 	return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_CLOCK_VAL_IN) != 0;
 }

 static int get_data(void *data)
 {
 	struct intel_gmbus *bus = data;
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	u32 reserved = get_reserved(bus);
 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved | GPIO_DATA_DIR_MASK);
 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
 	return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_DATA_VAL_IN) != 0;
 }

 static void set_clock(void *data, int state_high)
 {
 	struct intel_gmbus *bus = data;
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	u32 reserved = get_reserved(bus);
 	u32 clock_bits;

 	if (state_high)
 		clock_bits = GPIO_CLOCK_DIR_IN | GPIO_CLOCK_DIR_MASK;
 	else
 		clock_bits = GPIO_CLOCK_DIR_OUT | GPIO_CLOCK_DIR_MASK |
 			GPIO_CLOCK_VAL_MASK;

 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved | clock_bits);
 	POSTING_READ(bus->gpio_reg);
 }

 static void set_data(void *data, int state_high)
 {
 	struct intel_gmbus *bus = data;
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	u32 reserved = get_reserved(bus);
 	u32 data_bits;

 	if (state_high)
 		data_bits = GPIO_DATA_DIR_IN | GPIO_DATA_DIR_MASK;
 	else
 		data_bits = GPIO_DATA_DIR_OUT | GPIO_DATA_DIR_MASK |
 			GPIO_DATA_VAL_MASK;

 	I915_WRITE_NOTRACE(bus->gpio_reg, reserved | data_bits);
 	POSTING_READ(bus->gpio_reg);
 }

 static int
 intel_gpio_pre_xfer(struct i2c_adapter *adapter)
 {
 	struct intel_gmbus *bus = container_of(adapter,
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = bus->dev_priv;

 	intel_i2c_reset(dev_priv->dev);
 	intel_i2c_quirk_set(dev_priv, true);
 	set_data(bus, 1);
 	set_clock(bus, 1);
 	udelay(I2C_RISEFALL_TIME);
 	return 0;
 }

 static void
 intel_gpio_post_xfer(struct i2c_adapter *adapter)
 {
 	struct intel_gmbus *bus = container_of(adapter,
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = bus->dev_priv;

 	set_data(bus, 1);
 	set_clock(bus, 1);
 	intel_i2c_quirk_set(dev_priv, false);
 }

 static void
 intel_gpio_setup(struct intel_gmbus *bus, u32 pin)
 {
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	struct i2c_algo_bit_data *algo;

 	algo = &bus->bit_algo;

 	/* -1 to map pin pair to gmbus index */
 	bus->gpio_reg = dev_priv->gpio_mmio_base + gmbus_ports[pin - 1].reg;

 	bus->adapter.algo_data = algo;
 	algo->setsda = set_data;
 	algo->setscl = set_clock;
 	algo->getsda = get_data;
 	algo->getscl = get_clock;
 	algo->pre_xfer = intel_gpio_pre_xfer;
 	algo->post_xfer = intel_gpio_post_xfer;
 	algo->udelay = I2C_RISEFALL_TIME;
 	algo->timeout = usecs_to_jiffies(2200);
 	algo->data = bus;
 }

 static int
 gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
 		u32 gmbus1_index)
 {
 	int reg_offset = dev_priv->gpio_mmio_base;
 	u16 len = msg->len;
 	u8 *buf = msg->buf;

 	I915_WRITE(GMBUS1 + reg_offset,
 		   gmbus1_index |
 		   GMBUS_CYCLE_WAIT |
 		   (len << GMBUS_BYTE_COUNT_SHIFT) |
 		   (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) |
 		   GMBUS_SLAVE_READ | GMBUS_SW_RDY);
 	while (len) {
 		int ret;
 		u32 val, loop = 0;
 		u32 gmbus2;

 		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
 			       (GMBUS_SATOER | GMBUS_HW_RDY),
 			       50);
 		if (ret)
 			return -ETIMEDOUT;
 		if (gmbus2 & GMBUS_SATOER)
 			return -ENXIO;

 		val = I915_READ(GMBUS3 + reg_offset);
 		do {
 			*buf++ = val & 0xff;
 			val >>= 8;
 		} while (--len && ++loop < 4);
 	}

 	return 0;
 }

 static int
 gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
 {
 	int reg_offset = dev_priv->gpio_mmio_base;
 	u16 len = msg->len;
 	u8 *buf = msg->buf;
 	u32 val, loop;

 	val = loop = 0;
 	while (len && loop < 4) {
 		val |= *buf++ << (8 * loop++);
 		len -= 1;
 	}

 	I915_WRITE(GMBUS3 + reg_offset, val);
 	I915_WRITE(GMBUS1 + reg_offset,
 		   GMBUS_CYCLE_WAIT |
 		   (msg->len << GMBUS_BYTE_COUNT_SHIFT) |
 		   (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) |
 		   GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
 	while (len) {
 		int ret;
 		u32 gmbus2;

 		val = loop = 0;
 		do {
 			val |= *buf++ << (8 * loop);
 		} while (--len && ++loop < 4);

 		I915_WRITE(GMBUS3 + reg_offset, val);

 		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
 			       (GMBUS_SATOER | GMBUS_HW_RDY),
 			       50);
 		if (ret)
 			return -ETIMEDOUT;
 		if (gmbus2 & GMBUS_SATOER)
 			return -ENXIO;
 	}
 	return 0;
 }

 /*
  * The gmbus controller can combine a 1 or 2 byte write with a read that
  * immediately follows it by using an "INDEX" cycle.
  */
 static bool
 gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
 {
 	return (i + 1 < num &&
 		!(msgs[i].flags & I2C_M_RD) && msgs[i].len <= 2 &&
 		(msgs[i + 1].flags & I2C_M_RD));
 }

 static int
 gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
 {
 	int reg_offset = dev_priv->gpio_mmio_base;
 	u32 gmbus1_index = 0;
 	u32 gmbus5 = 0;
 	int ret;

 	if (msgs[0].len == 2)
 		gmbus5 = GMBUS_2BYTE_INDEX_EN |
 			 msgs[0].buf[1] | (msgs[0].buf[0] << 8);
 	if (msgs[0].len == 1)
 		gmbus1_index = GMBUS_CYCLE_INDEX |
 			       (msgs[0].buf[0] << GMBUS_SLAVE_INDEX_SHIFT);

 	/* GMBUS5 holds 16-bit index */
 	if (gmbus5)
 		I915_WRITE(GMBUS5 + reg_offset, gmbus5);

 	ret = gmbus_xfer_read(dev_priv, &msgs[1], gmbus1_index);

 	/* Clear GMBUS5 after each index transfer */
 	if (gmbus5)
 		I915_WRITE(GMBUS5 + reg_offset, 0);

 	return ret;
 }

 static int
 gmbus_xfer(struct i2c_adapter *adapter,
 	   struct i2c_msg *msgs,
 	   int num)
 {
 	struct intel_gmbus *bus = container_of(adapter,
 					       struct intel_gmbus,
 					       adapter);
 	struct drm_i915_private *dev_priv = bus->dev_priv;
 	int i, reg_offset;
 	int ret = 0;

 	mutex_lock(&dev_priv->gmbus_mutex);

 	if (bus->force_bit) {
 		ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
 		goto out;
 	}

 	reg_offset = dev_priv->gpio_mmio_base;

 	I915_WRITE(GMBUS0 + reg_offset, bus->reg0);

 	for (i = 0; i < num; i++) {
 		u32 gmbus2;

 		if (gmbus_is_index_read(msgs, i, num)) {
 			ret = gmbus_xfer_index_read(dev_priv, &msgs[i]);
 			i += 1;  /* set i to the index of the read xfer */
 		} else if (msgs[i].flags & I2C_M_RD) {
 			ret = gmbus_xfer_read(dev_priv, &msgs[i], 0);
 		} else {
 			ret = gmbus_xfer_write(dev_priv, &msgs[i]);
 		}

 		if (ret == -ETIMEDOUT)
 			goto timeout;
 		if (ret == -ENXIO)
 			goto clear_err;

 		ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
 			       (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE),
 			       50);
 		if (ret)
 			goto timeout;
 		if (gmbus2 & GMBUS_SATOER)
 			goto clear_err;
 	}

 	/* Generate a STOP condition on the bus. Note that gmbus can't generata
 	 * a STOP on the very first cycle. To simplify the code we
 	 * unconditionally generate the STOP condition with an additional gmbus
 	 * cycle. */
 	I915_WRITE(GMBUS1 + reg_offset, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);

 	/* Mark the GMBUS interface as disabled after waiting for idle.
 	 * We will re-enable it at the start of the next xfer,
 	 * till then let it sleep.
 	 */
 	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
 		     10)) {
 		DRM_DEBUG_KMS("GMBUS [%s] timed out waiting for idle\n",
 			 adapter->name);
 		ret = -ETIMEDOUT;
 	}
 	I915_WRITE(GMBUS0 + reg_offset, 0);
 	ret = ret ?: i;
 	goto out;

 clear_err:
 	/*
 	 * Wait for bus to IDLE before clearing NAK.
 	 * If we clear the NAK while bus is still active, then it will stay
 	 * active and the next transaction may fail.
 	 *
 	 * If no ACK is received during the address phase of a transaction, the
 	 * adapter must report -ENXIO. It is not clear what to return if no ACK
 	 * is received at other times. But we have to be careful to not return
 	 * spurious -ENXIO because that will prevent i2c and drm edid functions
 	 * from retrying. So return -ENXIO only when gmbus properly quiescents -
 	 * timing out seems to happen when there _is_ a ddc chip present, but
 	 * it's slow responding and only answers on the 2nd retry.
 	 */
 	ret = -ENXIO;
 	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
 		     10)) {
 		DRM_DEBUG_KMS("GMBUS [%s] timed out after NAK\n",
 			      adapter->name);
 		ret = -ETIMEDOUT;
 	}

 	/* Toggle the Software Clear Interrupt bit. This has the effect
 	 * of resetting the GMBUS controller and so clearing the
 	 * BUS_ERROR raised by the slave's NAK.
 	 */
 	I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT);
 	I915_WRITE(GMBUS1 + reg_offset, 0);
 	I915_WRITE(GMBUS0 + reg_offset, 0);

 	DRM_DEBUG_KMS("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
 			 adapter->name, msgs[i].addr,
 			 (msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len);

 	goto out;

 timeout:
 	DRM_INFO("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
 		 bus->adapter.name, bus->reg0 & 0xff);
 	I915_WRITE(GMBUS0 + reg_offset, 0);

 	/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
 	bus->force_bit = true;
 	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

 out:
 	mutex_unlock(&dev_priv->gmbus_mutex);
 	return ret;
 }

 static u32 gmbus_func(struct i2c_adapter *adapter)
 {
 	return i2c_bit_algo.functionality(adapter) &
 		(I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
 		/* I2C_FUNC_10BIT_ADDR | */
 		I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 		I2C_FUNC_SMBUS_BLOCK_PROC_CALL);
 }

 static const struct i2c_algorithm gmbus_algorithm = {
 	.master_xfer	= gmbus_xfer,
 	.functionality	= gmbus_func
 };

 /**
  * intel_gmbus_setup - instantiate all Intel i2c GMBuses
  * @dev: DRM device
  */
 int intel_setup_gmbus(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int ret, i;

 	if (HAS_PCH_SPLIT(dev))
 		dev_priv->gpio_mmio_base = PCH_GPIOA - GPIOA;
 	else
 		dev_priv->gpio_mmio_base = 0;

 	mutex_init(&dev_priv->gmbus_mutex);

 	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
 		u32 port = i + 1; /* +1 to map gmbus index to pin pair */

 		bus->adapter.owner = THIS_MODULE;
 		bus->adapter.class = I2C_CLASS_DDC;
 		snprintf(bus->adapter.name,
 			 sizeof(bus->adapter.name),
 			 "i915 gmbus %s",
 			 gmbus_ports[i].name);

 		bus->adapter.dev.parent = &dev->pdev->dev;
 		bus->dev_priv = dev_priv;

 		bus->adapter.algo = &gmbus_algorithm;

 		/* By default use a conservative clock rate */
 		bus->reg0 = port | GMBUS_RATE_100KHZ;

 		/* gmbus seems to be broken on i830 */
 		if (IS_I830(dev))
 			bus->force_bit = true;

 		intel_gpio_setup(bus, port);

 		ret = i2c_add_adapter(&bus->adapter);
 		if (ret)
 			goto err;
 	}

 	intel_i2c_reset(dev_priv->dev);

 	return 0;

 err:
 	while (--i) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
 		i2c_del_adapter(&bus->adapter);
 	}
 	return ret;
 }

 struct i2c_adapter *intel_gmbus_get_adapter(struct drm_i915_private *dev_priv,
 					    unsigned port)
 {
 	WARN_ON(!intel_gmbus_is_port_valid(port));
 	/* -1 to map pin pair to gmbus index */
 	return (intel_gmbus_is_port_valid(port)) ?
 		&dev_priv->gmbus[port - 1].adapter : NULL;
 }

 void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed)
 {
 	struct intel_gmbus *bus = to_intel_gmbus(adapter);

 	bus->reg0 = (bus->reg0 & ~(0x3 << 8)) | speed;
 }

 void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit)
 {
 	struct intel_gmbus *bus = to_intel_gmbus(adapter);

 	bus->force_bit = force_bit;
 }

 void intel_teardown_gmbus(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int i;

 	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
 		struct intel_gmbus *bus = &dev_priv->gmbus[i];
 		i2c_del_adapter(&bus->adapter);
 	}
 }
	/*
	* Copyright (c) 2006 Dave Airlie <airlied@linux.ie>
	* Copyright © 2006-2008,2010 Intel Corporation
	* Jesse Barnes <jesse.barnes@intel.com>
	*
	* 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.
	*
	* Authors:
	* Eric Anholt <eric@anholt.net>
	* Chris Wilson <chris@chris-wilson.co.uk>
	*/
	#include <linux/i2c.h>
	#include <linux/i2c-algo-bit.h>
	#include <linux/export.h>
	#include <drm/drmP.h>
	#include "intel_drv.h"
	#include <drm/i915_drm.h>
	#include "i915_drv.h"

	struct gmbus_port {
	const char *name;
	int reg;
	};

	static const struct gmbus_port gmbus_ports[] = {
	{ "ssc", GPIOB },
	{ "vga", GPIOA },
	{ "panel", GPIOC },
	{ "dpc", GPIOD },
	{ "dpb", GPIOE },
	{ "dpd", GPIOF },
	};

	/* Intel GPIO access functions */

	#define I2C_RISEFALL_TIME 10

	static inline struct intel_gmbus *
	to_intel_gmbus(struct i2c_adapter *i2c)
	{
	return container_of(i2c, struct intel_gmbus, adapter);
	}

	void
	intel_i2c_reset(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	I915_WRITE(dev_priv->gpio_mmio_base + GMBUS0, 0);
	}

	static void intel_i2c_quirk_set(struct drm_i915_private *dev_priv, bool enable)
	{
	u32 val;

	/* When using bit bashing for I2C, this bit needs to be set to 1 */
	if (!IS_PINEVIEW(dev_priv->dev))
	return;

	val = I915_READ(DSPCLK_GATE_D);
	if (enable)
	val \|= DPCUNIT_CLOCK_GATE_DISABLE;
	else
	val &= ~DPCUNIT_CLOCK_GATE_DISABLE;
	I915_WRITE(DSPCLK_GATE_D, val);
	}

	static u32 get_reserved(struct intel_gmbus *bus)
	{
	struct drm_i915_private *dev_priv = bus->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_NOTRACE(bus->gpio_reg) &
	(GPIO_DATA_PULLUP_DISABLE \|
	GPIO_CLOCK_PULLUP_DISABLE);

	return reserved;
	}

	static int get_clock(void *data)
	{
	struct intel_gmbus *bus = data;
	struct drm_i915_private *dev_priv = bus->dev_priv;
	u32 reserved = get_reserved(bus);
	I915_WRITE_NOTRACE(bus->gpio_reg, reserved \| GPIO_CLOCK_DIR_MASK);
	I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
	return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_CLOCK_VAL_IN) != 0;
	}

	static int get_data(void *data)
	{
	struct intel_gmbus *bus = data;
	struct drm_i915_private *dev_priv = bus->dev_priv;
	u32 reserved = get_reserved(bus);
	I915_WRITE_NOTRACE(bus->gpio_reg, reserved \| GPIO_DATA_DIR_MASK);
	I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
	return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_DATA_VAL_IN) != 0;
	}

	static void set_clock(void *data, int state_high)
	{
	struct intel_gmbus *bus = data;
	struct drm_i915_private *dev_priv = bus->dev_priv;
	u32 reserved = get_reserved(bus);
	u32 clock_bits;

	if (state_high)
	clock_bits = GPIO_CLOCK_DIR_IN \| GPIO_CLOCK_DIR_MASK;
	else
	clock_bits = GPIO_CLOCK_DIR_OUT \| GPIO_CLOCK_DIR_MASK \|
	GPIO_CLOCK_VAL_MASK;

	I915_WRITE_NOTRACE(bus->gpio_reg, reserved \| clock_bits);
	POSTING_READ(bus->gpio_reg);
	}

	static void set_data(void *data, int state_high)
	{
	struct intel_gmbus *bus = data;
	struct drm_i915_private *dev_priv = bus->dev_priv;
	u32 reserved = get_reserved(bus);
	u32 data_bits;

	if (state_high)
	data_bits = GPIO_DATA_DIR_IN \| GPIO_DATA_DIR_MASK;
	else
	data_bits = GPIO_DATA_DIR_OUT \| GPIO_DATA_DIR_MASK \|
	GPIO_DATA_VAL_MASK;

	I915_WRITE_NOTRACE(bus->gpio_reg, reserved \| data_bits);
	POSTING_READ(bus->gpio_reg);
	}

	static int
	intel_gpio_pre_xfer(struct i2c_adapter *adapter)
	{
	struct intel_gmbus *bus = container_of(adapter,
	struct intel_gmbus,
	adapter);
	struct drm_i915_private *dev_priv = bus->dev_priv;

	intel_i2c_reset(dev_priv->dev);
	intel_i2c_quirk_set(dev_priv, true);
	set_data(bus, 1);
	set_clock(bus, 1);
	udelay(I2C_RISEFALL_TIME);
	return 0;
	}

	static void
	intel_gpio_post_xfer(struct i2c_adapter *adapter)
	{
	struct intel_gmbus *bus = container_of(adapter,
	struct intel_gmbus,
	adapter);
	struct drm_i915_private *dev_priv = bus->dev_priv;

	set_data(bus, 1);
	set_clock(bus, 1);
	intel_i2c_quirk_set(dev_priv, false);
	}

	static void
	intel_gpio_setup(struct intel_gmbus *bus, u32 pin)
	{
	struct drm_i915_private *dev_priv = bus->dev_priv;
	struct i2c_algo_bit_data *algo;

	algo = &bus->bit_algo;

	/* -1 to map pin pair to gmbus index */
	bus->gpio_reg = dev_priv->gpio_mmio_base + gmbus_ports[pin - 1].reg;

	bus->adapter.algo_data = algo;
	algo->setsda = set_data;
	algo->setscl = set_clock;
	algo->getsda = get_data;
	algo->getscl = get_clock;
	algo->pre_xfer = intel_gpio_pre_xfer;
	algo->post_xfer = intel_gpio_post_xfer;
	algo->udelay = I2C_RISEFALL_TIME;
	algo->timeout = usecs_to_jiffies(2200);
	algo->data = bus;
	}

	static int
	gmbus_xfer_read(struct drm_i915_private dev_priv, struct i2c_msg msg,
	u32 gmbus1_index)
	{
	int reg_offset = dev_priv->gpio_mmio_base;
	u16 len = msg->len;
	u8 *buf = msg->buf;

	I915_WRITE(GMBUS1 + reg_offset,
	gmbus1_index \|
	GMBUS_CYCLE_WAIT \|
	(len << GMBUS_BYTE_COUNT_SHIFT) \|
	(msg->addr << GMBUS_SLAVE_ADDR_SHIFT) \|
	GMBUS_SLAVE_READ \| GMBUS_SW_RDY);
	while (len) {
	int ret;
	u32 val, loop = 0;
	u32 gmbus2;

	ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
	(GMBUS_SATOER \| GMBUS_HW_RDY),
	50);
	if (ret)
	return -ETIMEDOUT;
	if (gmbus2 & GMBUS_SATOER)
	return -ENXIO;

	val = I915_READ(GMBUS3 + reg_offset);
	do {
	*buf++ = val & 0xff;
	val >>= 8;
	} while (--len && ++loop < 4);
	}

	return 0;
	}

	static int
	gmbus_xfer_write(struct drm_i915_private dev_priv, struct i2c_msg msg)
	{
	int reg_offset = dev_priv->gpio_mmio_base;
	u16 len = msg->len;
	u8 *buf = msg->buf;
	u32 val, loop;

	val = loop = 0;
	while (len && loop < 4) {
	val \|= buf++ << (8 loop++);
	len -= 1;
	}

	I915_WRITE(GMBUS3 + reg_offset, val);
	I915_WRITE(GMBUS1 + reg_offset,
	GMBUS_CYCLE_WAIT \|
	(msg->len << GMBUS_BYTE_COUNT_SHIFT) \|
	(msg->addr << GMBUS_SLAVE_ADDR_SHIFT) \|
	GMBUS_SLAVE_WRITE \| GMBUS_SW_RDY);
	while (len) {
	int ret;
	u32 gmbus2;

	val = loop = 0;
	do {
	val \|= buf++ << (8 loop);
	} while (--len && ++loop < 4);

	I915_WRITE(GMBUS3 + reg_offset, val);

	ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
	(GMBUS_SATOER \| GMBUS_HW_RDY),
	50);
	if (ret)
	return -ETIMEDOUT;
	if (gmbus2 & GMBUS_SATOER)
	return -ENXIO;
	}
	return 0;
	}

	/*
	* The gmbus controller can combine a 1 or 2 byte write with a read that
	* immediately follows it by using an "INDEX" cycle.
	*/
	static bool
	gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
	{
	return (i + 1 < num &&
	!(msgs[i].flags & I2C_M_RD) && msgs[i].len <= 2 &&
	(msgs[i + 1].flags & I2C_M_RD));
	}

	static int
	gmbus_xfer_index_read(struct drm_i915_private dev_priv, struct i2c_msg msgs)
	{
	int reg_offset = dev_priv->gpio_mmio_base;
	u32 gmbus1_index = 0;
	u32 gmbus5 = 0;
	int ret;

	if (msgs[0].len == 2)
	gmbus5 = GMBUS_2BYTE_INDEX_EN \|
	msgs[0].buf[1] \| (msgs[0].buf[0] << 8);
	if (msgs[0].len == 1)
	gmbus1_index = GMBUS_CYCLE_INDEX \|
	(msgs[0].buf[0] << GMBUS_SLAVE_INDEX_SHIFT);

	/* GMBUS5 holds 16-bit index */
	if (gmbus5)
	I915_WRITE(GMBUS5 + reg_offset, gmbus5);

	ret = gmbus_xfer_read(dev_priv, &msgs[1], gmbus1_index);

	/* Clear GMBUS5 after each index transfer */
	if (gmbus5)
	I915_WRITE(GMBUS5 + reg_offset, 0);

	return ret;
	}

	static int
	gmbus_xfer(struct i2c_adapter *adapter,
	struct i2c_msg *msgs,
	int num)
	{
	struct intel_gmbus *bus = container_of(adapter,
	struct intel_gmbus,
	adapter);
	struct drm_i915_private *dev_priv = bus->dev_priv;
	int i, reg_offset;
	int ret = 0;

	mutex_lock(&dev_priv->gmbus_mutex);

	if (bus->force_bit) {
	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
	goto out;
	}

	reg_offset = dev_priv->gpio_mmio_base;

	I915_WRITE(GMBUS0 + reg_offset, bus->reg0);

	for (i = 0; i < num; i++) {
	u32 gmbus2;

	if (gmbus_is_index_read(msgs, i, num)) {
	ret = gmbus_xfer_index_read(dev_priv, &msgs[i]);
	i += 1; /* set i to the index of the read xfer */
	} else if (msgs[i].flags & I2C_M_RD) {
	ret = gmbus_xfer_read(dev_priv, &msgs[i], 0);
	} else {
	ret = gmbus_xfer_write(dev_priv, &msgs[i]);
	}

	if (ret == -ETIMEDOUT)
	goto timeout;
	if (ret == -ENXIO)
	goto clear_err;

	ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
	(GMBUS_SATOER \| GMBUS_HW_WAIT_PHASE),
	50);
	if (ret)
	goto timeout;
	if (gmbus2 & GMBUS_SATOER)
	goto clear_err;
	}

	/* Generate a STOP condition on the bus. Note that gmbus can't generata
	* a STOP on the very first cycle. To simplify the code we
	* unconditionally generate the STOP condition with an additional gmbus
	* cycle. */
	I915_WRITE(GMBUS1 + reg_offset, GMBUS_CYCLE_STOP \| GMBUS_SW_RDY);

	/* Mark the GMBUS interface as disabled after waiting for idle.
	* We will re-enable it at the start of the next xfer,
	* till then let it sleep.
	*/
	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
	10)) {
	DRM_DEBUG_KMS("GMBUS [%s] timed out waiting for idle\n",
	adapter->name);
	ret = -ETIMEDOUT;
	}
	I915_WRITE(GMBUS0 + reg_offset, 0);
	ret = ret ?: i;
	goto out;

	clear_err:
	/*
	* Wait for bus to IDLE before clearing NAK.
	* If we clear the NAK while bus is still active, then it will stay
	* active and the next transaction may fail.
	*
	* If no ACK is received during the address phase of a transaction, the
	* adapter must report -ENXIO. It is not clear what to return if no ACK
	* is received at other times. But we have to be careful to not return
	* spurious -ENXIO because that will prevent i2c and drm edid functions
	* from retrying. So return -ENXIO only when gmbus properly quiescents -
	* timing out seems to happen when there _is_ a ddc chip present, but
	* it's slow responding and only answers on the 2nd retry.
	*/
	ret = -ENXIO;
	if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
	10)) {
	DRM_DEBUG_KMS("GMBUS [%s] timed out after NAK\n",
	adapter->name);
	ret = -ETIMEDOUT;
	}

	/* Toggle the Software Clear Interrupt bit. This has the effect
	* of resetting the GMBUS controller and so clearing the
	* BUS_ERROR raised by the slave's NAK.
	*/
	I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT);
	I915_WRITE(GMBUS1 + reg_offset, 0);
	I915_WRITE(GMBUS0 + reg_offset, 0);

	DRM_DEBUG_KMS("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
	adapter->name, msgs[i].addr,
	(msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len);

	goto out;

	timeout:
	DRM_INFO("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
	bus->adapter.name, bus->reg0 & 0xff);
	I915_WRITE(GMBUS0 + reg_offset, 0);

	/* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
	bus->force_bit = true;
	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

	out:
	mutex_unlock(&dev_priv->gmbus_mutex);
	return ret;
	}

	static u32 gmbus_func(struct i2c_adapter *adapter)
	{
	return i2c_bit_algo.functionality(adapter) &
	(I2C_FUNC_I2C \| I2C_FUNC_SMBUS_EMUL \|
	/* I2C_FUNC_10BIT_ADDR \| */
	I2C_FUNC_SMBUS_READ_BLOCK_DATA \|
	I2C_FUNC_SMBUS_BLOCK_PROC_CALL);
	}

	static const struct i2c_algorithm gmbus_algorithm = {
	.master_xfer = gmbus_xfer,
	.functionality = gmbus_func
	};

	/**
	* intel_gmbus_setup - instantiate all Intel i2c GMBuses
	* @dev: DRM device
	*/
	int intel_setup_gmbus(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int ret, i;

	if (HAS_PCH_SPLIT(dev))
	dev_priv->gpio_mmio_base = PCH_GPIOA - GPIOA;
	else
	dev_priv->gpio_mmio_base = 0;

	mutex_init(&dev_priv->gmbus_mutex);

	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
	struct intel_gmbus *bus = &dev_priv->gmbus[i];
	u32 port = i + 1; /* +1 to map gmbus index to pin pair */

	bus->adapter.owner = THIS_MODULE;
	bus->adapter.class = I2C_CLASS_DDC;
	snprintf(bus->adapter.name,
	sizeof(bus->adapter.name),
	"i915 gmbus %s",
	gmbus_ports[i].name);

	bus->adapter.dev.parent = &dev->pdev->dev;
	bus->dev_priv = dev_priv;

	bus->adapter.algo = &gmbus_algorithm;

	/* By default use a conservative clock rate */
	bus->reg0 = port \| GMBUS_RATE_100KHZ;

	/* gmbus seems to be broken on i830 */
	if (IS_I830(dev))
	bus->force_bit = true;

	intel_gpio_setup(bus, port);

	ret = i2c_add_adapter(&bus->adapter);
	if (ret)
	goto err;
	}

	intel_i2c_reset(dev_priv->dev);

	return 0;

	err:
	while (--i) {
	struct intel_gmbus *bus = &dev_priv->gmbus[i];
	i2c_del_adapter(&bus->adapter);
	}
	return ret;
	}

	struct i2c_adapter intel_gmbus_get_adapter(struct drm_i915_private dev_priv,
	unsigned port)
	{
	WARN_ON(!intel_gmbus_is_port_valid(port));
	/* -1 to map pin pair to gmbus index */
	return (intel_gmbus_is_port_valid(port)) ?
	&dev_priv->gmbus[port - 1].adapter : NULL;
	}

	void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed)
	{
	struct intel_gmbus *bus = to_intel_gmbus(adapter);

	bus->reg0 = (bus->reg0 & ~(0x3 << 8)) \| speed;
	}

	void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit)
	{
	struct intel_gmbus *bus = to_intel_gmbus(adapter);

	bus->force_bit = force_bit;
	}

	void intel_teardown_gmbus(struct drm_device *dev)
	{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int i;

	for (i = 0; i < GMBUS_NUM_PORTS; i++) {
	struct intel_gmbus *bus = &dev_priv->gmbus[i];
	i2c_del_adapter(&bus->adapter);
	}
	}