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/*

 * Copyright (c) 2006 Dave Airlie 

 * Copyright © 2006-2008,2010 Intel Corporation

 *   Jesse Barnes 

 *

 * 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 

 *	Chris Wilson 

 */

#include 

#include 

#include 

#include 

#include "intel_drv.h"

#include 

#include "i915_drv.h"

struct gmbus_pin {

	const char *name;

	i915_reg_t reg;

};

/* Map gmbus pin pairs to names and registers. */

static const struct gmbus_pin gmbus_pins[] = {

	[GMBUS_PIN_SSC] = { "ssc", GPIOB },

	[GMBUS_PIN_VGADDC] = { "vga", GPIOA },

	[GMBUS_PIN_PANEL] = { "panel", GPIOC },

	[GMBUS_PIN_DPC] = { "dpc", GPIOD },

	[GMBUS_PIN_DPB] = { "dpb", GPIOE },

	[GMBUS_PIN_DPD] = { "dpd", GPIOF },

};

static const struct gmbus_pin gmbus_pins_bdw[] = {

	[GMBUS_PIN_VGADDC] = { "vga", GPIOA },

	[GMBUS_PIN_DPC] = { "dpc", GPIOD },

	[GMBUS_PIN_DPB] = { "dpb", GPIOE },

	[GMBUS_PIN_DPD] = { "dpd", GPIOF },

};

static const struct gmbus_pin gmbus_pins_skl[] = {

	[GMBUS_PIN_DPC] = { "dpc", GPIOD },

	[GMBUS_PIN_DPB] = { "dpb", GPIOE },

	[GMBUS_PIN_DPD] = { "dpd", GPIOF },

};

static const struct gmbus_pin gmbus_pins_bxt[] = {

	[GMBUS_PIN_1_BXT] = { "dpb", GPIOB },

	[GMBUS_PIN_2_BXT] = { "dpc", GPIOC },

	[GMBUS_PIN_3_BXT] = { "misc", GPIOD },

};

/* pin is expected to be valid */

static const struct gmbus_pin *get_gmbus_pin(struct drm_i915_private *dev_priv,

					     unsigned int pin)

{

	if (IS_BROXTON(dev_priv))

		return &gmbus_pins_bxt[pin];

	else if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))

		return &gmbus_pins_skl[pin];

	else if (IS_BROADWELL(dev_priv))

		return &gmbus_pins_bdw[pin];

	else

		return &gmbus_pins[pin];

}

bool intel_gmbus_is_valid_pin(struct drm_i915_private *dev_priv,

			      unsigned int pin)

{

	unsigned int size;

	if (IS_BROXTON(dev_priv))

		size = ARRAY_SIZE(gmbus_pins_bxt);

	else if (IS_SKYLAKE(dev_priv) || IS_KABYLAKE(dev_priv))

		size = ARRAY_SIZE(gmbus_pins_skl);

	else if (IS_BROADWELL(dev_priv))

		size = ARRAY_SIZE(gmbus_pins_bdw);

	else

		size = ARRAY_SIZE(gmbus_pins);

	return pin < size &&

		i915_mmio_reg_valid(get_gmbus_pin(dev_priv, pin)->reg);

}

/* 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(GMBUS0, 0);

	I915_WRITE(GMBUS4, 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, unsigned int pin)

{

	struct drm_i915_private *dev_priv = bus->dev_priv;

	struct i2c_algo_bit_data *algo;

	algo = &bus->bit_algo;

	bus->gpio_reg = _MMIO(dev_priv->gpio_mmio_base +

			      i915_mmio_reg_offset(get_gmbus_pin(dev_priv, pin)->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_wait_hw_status(struct drm_i915_private *dev_priv,

		     u32 gmbus2_status,

		     u32 gmbus4_irq_en)

{

	int i;

	u32 gmbus2 = 0;

	DEFINE_WAIT(wait);

	if (!HAS_GMBUS_IRQ(dev_priv->dev))

		gmbus4_irq_en = 0;

	/* Important: The hw handles only the first bit, so set only one! Since

	 * we also need to check for NAKs besides the hw ready/idle signal, we

	 * need to wake up periodically and check that ourselves. */

	I915_WRITE(GMBUS4, gmbus4_irq_en);

	for (i = 0; i < msecs_to_jiffies_timeout(50); i++) {

		prepare_to_wait(&dev_priv->gmbus_wait_queue, &wait,

				TASK_UNINTERRUPTIBLE);

		gmbus2 = I915_READ_NOTRACE(GMBUS2);

		if (gmbus2 & (GMBUS_SATOER | gmbus2_status))

			break;

		schedule_timeout(1);

	}

	finish_wait(&dev_priv->gmbus_wait_queue, &wait);

	I915_WRITE(GMBUS4, 0);

	if (gmbus2 & GMBUS_SATOER)

		return -ENXIO;

	if (gmbus2 & gmbus2_status)

		return 0;

	return -ETIMEDOUT;

}

static int

gmbus_wait_idle(struct drm_i915_private *dev_priv)

{

	int ret;

#define C ((I915_READ_NOTRACE(GMBUS2) & GMBUS_ACTIVE) == 0)

	if (!HAS_GMBUS_IRQ(dev_priv->dev))

		return wait_for(C, 10);

	/* Important: The hw handles only the first bit, so set only one! */

	I915_WRITE(GMBUS4, GMBUS_IDLE_EN);

	ret = wait_event_timeout(dev_priv->gmbus_wait_queue, C,

				 msecs_to_jiffies_timeout(10));

	I915_WRITE(GMBUS4, 0);

	if (ret)

		return 0;

	else

		return -ETIMEDOUT;

#undef C

}

static int

gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv,

		      unsigned short addr, u8 *buf, unsigned int len,

		      u32 gmbus1_index)

{

	I915_WRITE(GMBUS1,

		   gmbus1_index |

		   GMBUS_CYCLE_WAIT |

		   (len << GMBUS_BYTE_COUNT_SHIFT) |

		   (addr << GMBUS_SLAVE_ADDR_SHIFT) |

		   GMBUS_SLAVE_READ | GMBUS_SW_RDY);

	while (len) {

		int ret;

		u32 val, loop = 0;

		ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,

					   GMBUS_HW_RDY_EN);

		if (ret)

			return ret;

		val = I915_READ(GMBUS3);

		do {

			*buf++ = val & 0xff;

			val >>= 8;

		} while (--len && ++loop < 4);

	}

	return 0;

}

static int

gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,

		u32 gmbus1_index)

{

	u8 *buf = msg->buf;

	unsigned int rx_size = msg->len;

	unsigned int len;

	int ret;

	do {

		len = min(rx_size, GMBUS_BYTE_COUNT_MAX);

		ret = gmbus_xfer_read_chunk(dev_priv, msg->addr,

					    buf, len, gmbus1_index);

		if (ret)

			return ret;

		rx_size -= len;

		buf += len;

	} while (rx_size != 0);

	return 0;

}

static int

gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,

		       unsigned short addr, u8 *buf, unsigned int len)

{

	unsigned int chunk_size = len;

	u32 val, loop;

	val = loop = 0;

	while (len && loop < 4) {

		val |= *buf++ << (8 * loop++);

		len -= 1;

	}

	I915_WRITE(GMBUS3, val);

	I915_WRITE(GMBUS1,

		   GMBUS_CYCLE_WAIT |

		   (chunk_size << GMBUS_BYTE_COUNT_SHIFT) |

		   (addr << GMBUS_SLAVE_ADDR_SHIFT) |

		   GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);

	while (len) {

		int ret;

		val = loop = 0;

		do {

			val |= *buf++ << (8 * loop);

		} while (--len && ++loop < 4);

		I915_WRITE(GMBUS3, val);

		ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,

					   GMBUS_HW_RDY_EN);

		if (ret)

			return ret;

	}

	return 0;

}

static int

gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)

{

	u8 *buf = msg->buf;

	unsigned int tx_size = msg->len;

	unsigned int len;

	int ret;

	do {

		len = min(tx_size, GMBUS_BYTE_COUNT_MAX);

		ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len);

		if (ret)

			return ret;

		buf += len;

		tx_size -= len;

	} while (tx_size != 0);

	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)

{

	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, gmbus5);

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

	/* Clear GMBUS5 after each index transfer */

	if (gmbus5)

		I915_WRITE(GMBUS5, 0);

	return ret;

}

static int

do_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 = 0, inc, try = 0;

	int ret = 0;

retry:

	I915_WRITE(GMBUS0, bus->reg0);

	for (; i < num; i += inc) {

		inc = 1;

		if (gmbus_is_index_read(msgs, i, num)) {

			ret = gmbus_xfer_index_read(dev_priv, &msgs[i]);

			inc = 2; /* an index read is two msgs */

		} 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)

			ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_WAIT_PHASE,

						   GMBUS_HW_WAIT_EN);

		if (ret == -ETIMEDOUT)

			goto timeout;

		else if (ret)

			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, 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 (gmbus_wait_idle(dev_priv)) {

		DRM_DEBUG_KMS("GMBUS [%s] timed out waiting for idle\n",

			 adapter->name);

		ret = -ETIMEDOUT;

	}

	I915_WRITE(GMBUS0, 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 (gmbus_wait_idle(dev_priv)) {

		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, GMBUS_SW_CLR_INT);

	I915_WRITE(GMBUS1, 0);

	I915_WRITE(GMBUS0, 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);

	/*

	 * Passive adapters sometimes NAK the first probe. Retry the first

	 * message once on -ENXIO for GMBUS transfers; the bit banging algorithm

	 * has retries internally. See also the retry loop in

	 * drm_do_probe_ddc_edid, which bails out on the first -ENXIO.

	 */

	if (ret == -ENXIO && i == 0 && try++ == 0) {

		DRM_DEBUG_KMS("GMBUS [%s] NAK on first message, retry\n",

			      adapter->name);

		goto retry;

	}

	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, 0);

	/*

	 * Hardware may not support GMBUS over these pins? Try GPIO bitbanging

	 * instead. Use EAGAIN to have i2c core retry.

	 */

	bus->force_bit = 1;

	ret = -EAGAIN;

out:

	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 ret;

	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);

	mutex_lock(&dev_priv->gmbus_mutex);

	if (bus->force_bit)

	ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

	else

		ret = do_gmbus_xfer(adapter, msgs, num);

	mutex_unlock(&dev_priv->gmbus_mutex);

	intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS);

	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;

	struct intel_gmbus *bus;

	unsigned int pin;

	int ret;

	if (HAS_PCH_NOP(dev))

		return 0;

	if (IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev))

		dev_priv->gpio_mmio_base = VLV_DISPLAY_BASE;

	else if (!HAS_GMCH_DISPLAY(dev_priv))

		dev_priv->gpio_mmio_base =

			i915_mmio_reg_offset(PCH_GPIOA) -

			i915_mmio_reg_offset(GPIOA);

	mutex_init(&dev_priv->gmbus_mutex);

	init_waitqueue_head(&dev_priv->gmbus_wait_queue);

	for (pin = 0; pin < ARRAY_SIZE(dev_priv->gmbus); pin++) {

		if (!intel_gmbus_is_valid_pin(dev_priv, pin))

			continue;

		bus = &dev_priv->gmbus[pin];

		bus->adapter.owner = THIS_MODULE;

		bus->adapter.class = I2C_CLASS_DDC;

		snprintf(bus->adapter.name,

			 sizeof(bus->adapter.name),

			 "i915 gmbus %s",

			 get_gmbus_pin(dev_priv, pin)->name);

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

		bus->dev_priv = dev_priv;

		bus->adapter.algo = &gmbus_algorithm;

		/*

		 * We wish to retry with bit banging

		 * after a timed out GMBUS attempt.

		 */

		bus->adapter.retries = 1;

		/* By default use a conservative clock rate */

		bus->reg0 = pin | GMBUS_RATE_100KHZ;

		/* gmbus seems to be broken on i830 */

		if (IS_I830(dev))

			bus->force_bit = 1;

		intel_gpio_setup(bus, pin);

		ret = i2c_add_adapter(&bus->adapter);

		if (ret)

			goto err;

	}

	intel_i2c_reset(dev_priv->dev);

	return 0;

err:

	while (pin--) {

		if (!intel_gmbus_is_valid_pin(dev_priv, pin))

			continue;

		bus = &dev_priv->gmbus[pin];

		i2c_del_adapter(&bus->adapter);

	}

	return ret;

}

struct i2c_adapter *intel_gmbus_get_adapter(struct drm_i915_private *dev_priv,

					    unsigned int pin)

{

	if (WARN_ON(!intel_gmbus_is_valid_pin(dev_priv, pin)))

		return NULL;

	return &dev_priv->gmbus[pin].adapter;

}

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 ? 1 : -1;

	DRM_DEBUG_KMS("%sabling bit-banging on %s. force bit now %d\n",

		      force_bit ? "en" : "dis", adapter->name,

		      bus->force_bit);

}

void intel_teardown_gmbus(struct drm_device *dev)

{

	struct drm_i915_private *dev_priv = dev->dev_private;

	struct intel_gmbus *bus;

	unsigned int pin;

	for (pin = 0; pin < ARRAY_SIZE(dev_priv->gmbus); pin++) {

		if (!intel_gmbus_is_valid_pin(dev_priv, pin))

			continue;

		bus = &dev_priv->gmbus[pin];

		i2c_del_adapter(&bus->adapter);

	}

}