linux/drivers/gpu/drm/gma500/intel_i2c.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright © 2006-2007 Intel Corporation
 *
 * Authors:
 *	Eric Anholt <eric@anholt.net>
 */

#include <linux/delay.h>
#include <linux/export.h>
#include <linux/i2c-algo-bit.h>
#include <linux/i2c.h>

#include "psb_drv.h"
#include "psb_intel_reg.h"

/*
 * Intel GPIO access functions
 */

#define I2C_RISEFALL_TIME 20

static int get_clock(void *data)
{
	struct psb_intel_i2c_chan *chan = data;
	struct drm_device *dev = chan->drm_dev;
	u32 val;

	val = REG_READ(chan->reg);
	return (val & GPIO_CLOCK_VAL_IN) != 0;
}

static int get_data(void *data)
{
	struct psb_intel_i2c_chan *chan = data;
	struct drm_device *dev = chan->drm_dev;
	u32 val;

	val = REG_READ(chan->reg);
	return (val & GPIO_DATA_VAL_IN) != 0;
}

static void set_clock(void *data, int state_high)
{
	struct psb_intel_i2c_chan *chan = data;
	struct drm_device *dev = chan->drm_dev;
	u32 reserved = 0, clock_bits;

	/* On most chips, these bits must be preserved in software. */
	reserved =
		    REG_READ(chan->reg) & (GPIO_DATA_PULLUP_DISABLE |
					   GPIO_CLOCK_PULLUP_DISABLE);

	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;
	REG_WRITE(chan->reg, reserved | clock_bits);
	udelay(I2C_RISEFALL_TIME);	/* wait for the line to change state */
}

static void set_data(void *data, int state_high)
{
	struct psb_intel_i2c_chan *chan = data;
	struct drm_device *dev = chan->drm_dev;
	u32 reserved = 0, data_bits;

	/* On most chips, these bits must be preserved in software. */
	reserved =
		    REG_READ(chan->reg) & (GPIO_DATA_PULLUP_DISABLE |
					   GPIO_CLOCK_PULLUP_DISABLE);

	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;

	REG_WRITE(chan->reg, reserved | data_bits);
	udelay(I2C_RISEFALL_TIME);	/* wait for the line to change state */
}

/**
 * psb_intel_i2c_create - instantiate an Intel i2c bus using the specified GPIO reg
 * @dev: DRM device
 * @reg: GPIO reg to use
 * @name: name for this bus
 *
 * Creates and registers a new i2c bus with the Linux i2c layer, for use
 * in output probing and control (e.g. DDC or SDVO control functions).
 *
 * Possible values for @reg include:
 *   %GPIOA
 *   %GPIOB
 *   %GPIOC
 *   %GPIOD
 *   %GPIOE
 *   %GPIOF
 *   %GPIOG
 *   %GPIOH
 * see PRM for details on how these different busses are used.
 */
struct psb_intel_i2c_chan *psb_intel_i2c_create(struct drm_device *dev,
					const u32 reg, const char *name)
{
	struct psb_intel_i2c_chan *chan;

	chan = kzalloc(sizeof(struct psb_intel_i2c_chan), GFP_KERNEL);
	if (!chan)
		goto out_free;

	chan->drm_dev = dev;
	chan->reg = reg;
	snprintf(chan->adapter.name, I2C_NAME_SIZE, "intel drm %s", name);
	chan->adapter.owner = THIS_MODULE;
	chan->adapter.algo_data = &chan->algo;
	chan->adapter.dev.parent = dev->dev;
	chan->algo.setsda = set_data;
	chan->algo.setscl = set_clock;
	chan->algo.getsda = get_data;
	chan->algo.getscl = get_clock;
	chan->algo.udelay = 20;
	chan->algo.timeout = usecs_to_jiffies(2200);
	chan->algo.data = chan;

	i2c_set_adapdata(&chan->adapter, chan);

	if (i2c_bit_add_bus(&chan->adapter))
		goto out_free;

	/* JJJ:  raise SCL and SDA? */
	set_data(chan, 1);
	set_clock(chan, 1);
	udelay(20);

	return chan;

out_free:
	kfree(chan);
	return NULL;
}

/**
 * psb_intel_i2c_destroy - unregister and free i2c bus resources
 * @chan: channel to free
 *
 * Unregister the adapter from the i2c layer, then free the structure.
 */
void psb_intel_i2c_destroy(struct psb_intel_i2c_chan *chan)
{
	if (!chan)
		return;

	i2c_del_adapter(&chan->adapter);
	kfree(chan);
}