linux/drivers/i2c/busses/i2c-icy.c

// SPDX-License-Identifier: GPL-2.0
/*
 * I2C driver for stand-alone PCF8584 style adapters on Zorro cards
 *
 * Original ICY documentation can be found on Aminet:
 * https://aminet.net/package/docs/hard/icy
 *
 * There has been a modern community re-print of this design in 2019:
 * https://www.a1k.org/forum/index.php?threads/70106/
 *
 * The card is basically a Philips PCF8584 connected straight to the
 * beginning of the AutoConfig'd address space (register S1 on base+2),
 * with /INT on /INT2 on the Zorro bus.
 *
 * Copyright (c) 2019 Max Staudt <max@enpas.org>
 *
 * This started as a fork of i2c-elektor.c and has evolved since.
 * Thanks go to its authors for providing a base to grow on.
 *
 *
 * IRQ support is currently not implemented.
 *
 * As it turns out, i2c-algo-pcf is really written with i2c-elektor's
 * edge-triggered ISA interrupts in mind, while the Amiga's Zorro bus has
 * level-triggered interrupts. This means that once an interrupt occurs, we
 * have to tell the PCF8584 to shut up immediately, or it will keep the
 * interrupt line busy and cause an IRQ storm.

 * However, because of the PCF8584's host-side protocol, there is no good
 * way to just quieten it without side effects. Rather, we have to perform
 * the next read/write operation straight away, which will reset the /INT
 * pin. This entails re-designing the core of i2c-algo-pcf in the future.
 * For now, we never request an IRQ from the PCF8584, and poll it instead.
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/i2c-algo-pcf.h>

#include <asm/amigaints.h>
#include <linux/zorro.h>

#include "../algos/i2c-algo-pcf.h"

struct icy_i2c {
	struct i2c_adapter adapter;

	void __iomem *reg_s0;
	void __iomem *reg_s1;
	struct fwnode_handle *ltc2990_fwnode;
	struct i2c_client *ltc2990_client;
};

/*
 * Functions called by i2c-algo-pcf
 */
static void icy_pcf_setpcf(void *data, int ctl, int val)
{
	struct icy_i2c *i2c = (struct icy_i2c *)data;

	u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;

	z_writeb(val, address);
}

static int icy_pcf_getpcf(void *data, int ctl)
{
	struct icy_i2c *i2c = (struct icy_i2c *)data;

	u8 __iomem *address = ctl ? i2c->reg_s1 : i2c->reg_s0;

	return z_readb(address);
}

static int icy_pcf_getown(void *data)
{
	return 0x55;
}

static int icy_pcf_getclock(void *data)
{
	return 0x1c;
}

static void icy_pcf_waitforpin(void *data)
{
	usleep_range(50, 150);
}

/*
 * Main i2c-icy part
 */
static unsigned short const icy_ltc2990_addresses[] = {
	0x4c, 0x4d, 0x4e, 0x4f, I2C_CLIENT_END
};

/*
 * Additional sensors exposed once this property is applied:
 *
 * in1 will be the voltage of the 5V rail, divided by 2.
 * in2 will be the voltage of the 12V rail, divided by 4.
 * temp3 will be measured using a PCB loop next the chip.
 */
static const u32 icy_ltc2990_meas_mode[] = {0, 3};

static const struct property_entry icy_ltc2990_props[] = {
	PROPERTY_ENTRY_U32_ARRAY("lltc,meas-mode", icy_ltc2990_meas_mode),
	{ }
};

static int icy_probe(struct zorro_dev *z,
		     const struct zorro_device_id *ent)
{
	struct icy_i2c *i2c;
	struct i2c_algo_pcf_data *algo_data;
	struct fwnode_handle *new_fwnode;
	struct i2c_board_info ltc2990_info = {
		.type		= "ltc2990",
	};

	i2c = devm_kzalloc(&z->dev, sizeof(*i2c), GFP_KERNEL);
	if (!i2c)
		return -ENOMEM;

	algo_data = devm_kzalloc(&z->dev, sizeof(*algo_data), GFP_KERNEL);
	if (!algo_data)
		return -ENOMEM;

	dev_set_drvdata(&z->dev, i2c);
	i2c->adapter.dev.parent = &z->dev;
	i2c->adapter.owner = THIS_MODULE;
	/* i2c->adapter.algo assigned by i2c_pcf_add_bus() */
	i2c->adapter.algo_data = algo_data;
	strlcpy(i2c->adapter.name, "ICY I2C Zorro adapter",
		sizeof(i2c->adapter.name));

	if (!devm_request_mem_region(&z->dev,
				     z->resource.start,
				     4, i2c->adapter.name))
		return -ENXIO;

	/* Driver private data */
	i2c->reg_s0 = ZTWO_VADDR(z->resource.start);
	i2c->reg_s1 = ZTWO_VADDR(z->resource.start + 2);

	algo_data->data = i2c;
	algo_data->setpcf     = icy_pcf_setpcf;
	algo_data->getpcf     = icy_pcf_getpcf;
	algo_data->getown     = icy_pcf_getown;
	algo_data->getclock   = icy_pcf_getclock;
	algo_data->waitforpin = icy_pcf_waitforpin;

	if (i2c_pcf_add_bus(&i2c->adapter)) {
		dev_err(&z->dev, "i2c_pcf_add_bus() failed\n");
		return -ENXIO;
	}

	dev_info(&z->dev, "ICY I2C controller at %pa, IRQ not implemented\n",
		 &z->resource.start);

	/*
	 * The 2019 a1k.org PCBs have an LTC2990 at 0x4c, so start
	 * it automatically once ltc2990 is modprobed.
	 *
	 * in0 is the voltage of the internal 5V power supply.
	 * temp1 is the temperature inside the chip.
	 *
	 * See property_entry above for in1, in2, temp3.
	 */
	new_fwnode = fwnode_create_software_node(icy_ltc2990_props, NULL);
	if (IS_ERR(new_fwnode)) {
		dev_info(&z->dev, "Failed to create fwnode for LTC2990, error: %ld\n",
			 PTR_ERR(new_fwnode));
	} else {
		/*
		 * Store the fwnode so we can destroy it on .remove().
		 * Only store it on success, as fwnode_remove_software_node()
		 * is NULL safe, but not PTR_ERR safe.
		 */
		i2c->ltc2990_fwnode = new_fwnode;
		ltc2990_info.fwnode = new_fwnode;

		i2c->ltc2990_client =
			i2c_new_scanned_device(&i2c->adapter,
					       &ltc2990_info,
					       icy_ltc2990_addresses,
					       NULL);
	}

	return 0;
}

static void icy_remove(struct zorro_dev *z)
{
	struct icy_i2c *i2c = dev_get_drvdata(&z->dev);

	i2c_unregister_device(i2c->ltc2990_client);
	fwnode_remove_software_node(i2c->ltc2990_fwnode);

	i2c_del_adapter(&i2c->adapter);
}

static const struct zorro_device_id icy_zorro_tbl[] = {
	{ ZORRO_ID(VMC, 15, 0), },
	{ 0 }
};

MODULE_DEVICE_TABLE(zorro, icy_zorro_tbl);

static struct zorro_driver icy_driver = {
	.name           = "i2c-icy",
	.id_table       = icy_zorro_tbl,
	.probe          = icy_probe,
	.remove         = icy_remove,
};

module_driver(icy_driver,
	      zorro_register_driver,
	      zorro_unregister_driver);

MODULE_AUTHOR("Max Staudt <max@enpas.org>");
MODULE_DESCRIPTION("I2C bus via PCF8584 on ICY Zorro card");
MODULE_LICENSE("GPL v2");