// SPDX-License-Identifier: GPL-2.0-or-later/* * ee1004 - driver for DDR4 SPD EEPROMs * * Copyright (C) 2017-2019 Jean Delvare * * Based on the at24 driver: * Copyright (C) 2005-2007 David Brownell * Copyright (C) 2008 Wolfram Sang, Pengutronix */ #include <linux/device.h>#include <linux/i2c.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/mutex.h>#include <linux/nvmem-provider.h> /* * DDR4 memory modules use special EEPROMs following the Jedec EE1004 * specification. These are 512-byte EEPROMs using a single I2C address * in the 0x50-0x57 range for data. One of two 256-byte page is selected * by writing a command to I2C address 0x36 or 0x37 on the same I2C bus. * * Therefore we need to request these 2 additional addresses, and serialize * access to all such EEPROMs with a single mutex. * * We assume it is safe to read up to 32 bytes at once from these EEPROMs. * We use SMBus access even if I2C is available, these EEPROMs are small * enough, and reading from them infrequent enough, that we favor simplicity * over performance. */ #define EE1004_MAX_BUSSES		8#define EE1004_ADDR_SET_PAGE		0x36#define EE1004_NUM_PAGES		2#define EE1004_PAGE_SIZE		256#define EE1004_PAGE_SHIFT		8#define EE1004_EEPROM_SIZE		(EE1004_PAGE_SIZE * EE1004_NUM_PAGES) /* * Mutex protects ee1004_set_page and ee1004_dev_count, and must be held * from page selection to end of read. */static DEFINE_MUTEX(ee1004_bus_lock); static struct ee1004_bus_data {	struct i2c_adapter *adap;	struct i2c_client *set_page[EE1004_NUM_PAGES];	unsigned int dev_count;	int current_page;} ee1004_bus_data[EE1004_MAX_BUSSES]; static const struct i2c_device_id ee1004_ids[] = {	{ "ee1004" },	{ }};MODULE_DEVICE_TABLE(i2c, ee1004_ids); /*-------------------------------------------------------------------------*/ static struct ee1004_bus_data *ee1004_get_bus_data(struct i2c_adapter *adap){	int i; 	for (i = 0; i < EE1004_MAX_BUSSES; i++)		if (ee1004_bus_data[i].adap == adap)			return ee1004_bus_data + i; 	/* If not existent yet, create new entry */	for (i = 0; i < EE1004_MAX_BUSSES; i++)		if (!ee1004_bus_data[i].adap) {			ee1004_bus_data[i].adap = adap;			return ee1004_bus_data + i;		} 	return NULL;} static int ee1004_get_current_page(struct ee1004_bus_data *bd){	int err; 	err = i2c_smbus_read_byte(bd->set_page[0]);	if (err == -ENXIO) {		/* Nack means page 1 is selected */		return 1;	}	if (err < 0) {		/* Anything else is a real error, bail out */		return err;	} 	/* Ack means page 0 is selected, returned value meaningless */	return 0;} static int ee1004_set_current_page(struct i2c_client *client, int page){	struct ee1004_bus_data *bd = i2c_get_clientdata(client);	int ret; 	if (page == bd->current_page)		return 0; 	/* Data is ignored */	ret = i2c_smbus_write_byte(bd->set_page[page], 0x00);	/*	 * Don't give up just yet. Some memory modules will select the page	 * but not ack the command. Check which page is selected now.	 */	if (ret == -ENXIO && ee1004_get_current_page(bd) == page)		ret = 0;	if (ret < 0) {		dev_err(&client->dev, "Failed to select page %d (%d)\n", page, ret);		return ret;	} 	dev_dbg(&client->dev, "Selected page %d\n", page);	bd->current_page = page; 	return 0;} static ssize_t ee1004_eeprom_read(struct i2c_client *client, char *buf,				  unsigned int offset, size_t count){	int status, page; 	page = offset >> EE1004_PAGE_SHIFT;	offset &= (1 << EE1004_PAGE_SHIFT) - 1; 	status = ee1004_set_current_page(client, page);	if (status)		return status; 	/* Can't cross page boundaries */	if (offset + count > EE1004_PAGE_SIZE)		count = EE1004_PAGE_SIZE - offset; 	if (count > I2C_SMBUS_BLOCK_MAX)		count = I2C_SMBUS_BLOCK_MAX; 	return i2c_smbus_read_i2c_block_data_or_emulated(client, offset, count, buf);} static int ee1004_read(void *priv, unsigned int off, void *val, size_t count){	struct i2c_client *client = priv;	char *buf = val;	int ret; 	if (unlikely(!count))		return count; 	if (off + count > EE1004_EEPROM_SIZE)		return -EINVAL; 	/*	 * Read data from chip, protecting against concurrent access to	 * other EE1004 SPD EEPROMs on the same adapter.	 */	mutex_lock(&ee1004_bus_lock); 	while (count) {		ret = ee1004_eeprom_read(client, buf, off, count);		if (ret < 0) {			mutex_unlock(&ee1004_bus_lock);			return ret;		} 		buf += ret;		off += ret;		count -= ret;	} 	mutex_unlock(&ee1004_bus_lock); 	return 0;} static void ee1004_probe_temp_sensor(struct i2c_client *client){	struct i2c_board_info info = { .type = "jc42" };	unsigned short addr = 0x18 | (client->addr & 7);	unsigned short addr_list[] = { addr, I2C_CLIENT_END };	u8 data[2];	int ret; 	/* byte 14, bit 7 is set if temp sensor is present */	ret = ee1004_eeprom_read(client, data, 14, 1);	if (ret != 1)		return; 	if (!(data[0] & BIT(7))) {		/*		 * If the SPD data suggests that there is no temperature		 * sensor, it may still be there for SPD revision 1.0.		 * See SPD Annex L, Revision 1 and 2, for details.		 * Check DIMM type and SPD revision; if it is a DDR4		 * with SPD revision 1.0, check the thermal sensor address		 * and instantiate the jc42 driver if a chip is found at		 * that address.		 * It is not necessary to check if there is a chip at the		 * temperature sensor address since i2c_new_scanned_device()		 * will do that and return silently if no chip is found.		 */		ret = ee1004_eeprom_read(client, data, 1, 2);		if (ret != 2 || data[0] != 0x10 || data[1] != 0x0c)			return;	}	i2c_new_scanned_device(client->adapter, &info, addr_list, NULL);} static void ee1004_cleanup(int idx, struct ee1004_bus_data *bd){	if (--bd->dev_count == 0) {		while (--idx >= 0)			i2c_unregister_device(bd->set_page[idx]);		memset(bd, 0, sizeof(struct ee1004_bus_data));	}} static void ee1004_cleanup_bus_data(void *data){	struct ee1004_bus_data *bd = data; 	/* Remove page select clients if this is the last device */	mutex_lock(&ee1004_bus_lock);	ee1004_cleanup(EE1004_NUM_PAGES, bd);	mutex_unlock(&ee1004_bus_lock);} static int ee1004_init_bus_data(struct i2c_client *client){	struct ee1004_bus_data *bd;	int err, cnr = 0; 	bd = ee1004_get_bus_data(client->adapter);	if (!bd)		return dev_err_probe(&client->dev, -ENOSPC, "Only %d busses supported",				     EE1004_MAX_BUSSES); 	i2c_set_clientdata(client, bd); 	if (++bd->dev_count == 1) {		/* Use 2 dummy devices for page select command */		for (cnr = 0; cnr < EE1004_NUM_PAGES; cnr++) {			struct i2c_client *cl; 			cl = i2c_new_dummy_device(client->adapter, EE1004_ADDR_SET_PAGE + cnr);			if (IS_ERR(cl)) {				err = PTR_ERR(cl);				goto err_out;			} 			bd->set_page[cnr] = cl;		} 		/* Remember current page to avoid unneeded page select */		err = ee1004_get_current_page(bd);		if (err < 0)			goto err_out; 		dev_dbg(&client->dev, "Currently selected page: %d\n", err);		bd->current_page = err;	} 	return 0; err_out:	ee1004_cleanup(cnr, bd); 	return err;} static int ee1004_probe(struct i2c_client *client){	struct nvmem_config config = {		.dev = &client->dev,		.name = dev_name(&client->dev),		.id = NVMEM_DEVID_NONE,		.owner = THIS_MODULE,		.type = NVMEM_TYPE_EEPROM,		.read_only = true,		.root_only = false,		.reg_read = ee1004_read,		.size = EE1004_EEPROM_SIZE,		.word_size = 1,		.stride = 1,		.priv = client,		.compat = true,		.base_dev = &client->dev,	};	struct nvmem_device *ndev;	int err; 	/* Make sure we can operate on this adapter */	if (!i2c_check_functionality(client->adapter,				     I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_READ_I2C_BLOCK) &&	    !i2c_check_functionality(client->adapter,				     I2C_FUNC_SMBUS_BYTE | I2C_FUNC_SMBUS_READ_BYTE_DATA))		return -EPFNOSUPPORT; 	err = i2c_smbus_read_byte(client);	if (err < 0)		return -ENODEV; 	mutex_lock(&ee1004_bus_lock); 	err = ee1004_init_bus_data(client);	if (err < 0) {		mutex_unlock(&ee1004_bus_lock);		return err;	} 	ee1004_probe_temp_sensor(client); 	mutex_unlock(&ee1004_bus_lock); 	err = devm_add_action_or_reset(&client->dev, ee1004_cleanup_bus_data,				       i2c_get_clientdata(client));	if (err < 0)		return err; 	ndev = devm_nvmem_register(&client->dev, &config);	if (IS_ERR(ndev))		return PTR_ERR(ndev); 	dev_info(&client->dev,		 "%u byte EE1004-compliant SPD EEPROM, read-only\n",		 EE1004_EEPROM_SIZE); 	return 0;} /*-------------------------------------------------------------------------*/ static struct i2c_driver ee1004_driver = {	.driver = {		.name = "ee1004",	},	.probe = ee1004_probe,	.id_table = ee1004_ids,};module_i2c_driver(ee1004_driver); MODULE_DESCRIPTION("Driver for EE1004-compliant DDR4 SPD EEPROMs");MODULE_AUTHOR("Jean Delvare");MODULE_LICENSE("GPL");