Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 245 insertions, 0 deletions

diff --git a/drivers/misc/eeprom/ee1004.c b/drivers/misc/eeprom/ee1004.c
new file mode 100644
index 0000000000..a1acd77130
--- /dev/null
+++ b/drivers/misc/eeprom/ee1004.c
@@ -0,0 +1,245 @@
+// 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/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/mutex.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_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 i2c_client *ee1004_set_page[EE1004_NUM_PAGES];
+static unsigned int ee1004_dev_count;
+static int ee1004_current_page;
+
+static const struct i2c_device_id ee1004_ids[] = {
+	{ "ee1004", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ee1004_ids);
+
+/*-------------------------------------------------------------------------*/
+
+static int ee1004_get_current_page(void)
+{
+	int err;
+
+	err = i2c_smbus_read_byte(ee1004_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 device *dev, int page)
+{
+	int ret;
+
+	if (page == ee1004_current_page)
+		return 0;
+
+	/* Data is ignored */
+	ret = i2c_smbus_write_byte(ee1004_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() == page)
+		ret = 0;
+	if (ret < 0) {
+		dev_err(dev, "Failed to select page %d (%d)\n", page, ret);
+		return ret;
+	}
+
+	dev_dbg(dev, "Selected page %d\n", page);
+	ee1004_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->dev, 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 ssize_t eeprom_read(struct file *filp, struct kobject *kobj,
+			   struct bin_attribute *bin_attr,
+			   char *buf, loff_t off, size_t count)
+{
+	struct i2c_client *client = kobj_to_i2c_client(kobj);
+	size_t requested = count;
+	int ret = 0;
+
+	/*
+	 * 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)
+			goto out;
+
+		buf += ret;
+		off += ret;
+		count -= ret;
+	}
+out:
+	mutex_unlock(&ee1004_bus_lock);
+
+	return ret < 0 ? ret : requested;
+}
+
+static BIN_ATTR_RO(eeprom, EE1004_EEPROM_SIZE);
+
+static struct bin_attribute *ee1004_attrs[] = {
+	&bin_attr_eeprom,
+	NULL
+};
+
+BIN_ATTRIBUTE_GROUPS(ee1004);
+
+static void ee1004_cleanup(int idx)
+{
+	if (--ee1004_dev_count == 0)
+		while (--idx >= 0) {
+			i2c_unregister_device(ee1004_set_page[idx]);
+			ee1004_set_page[idx] = NULL;
+		}
+}
+
+static int ee1004_probe(struct i2c_client *client)
+{
+	int err, cnr = 0;
+
+	/* 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;
+
+	/* Use 2 dummy devices for page select command */
+	mutex_lock(&ee1004_bus_lock);
+	if (++ee1004_dev_count == 1) {
+		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_clients;
+			}
+			ee1004_set_page[cnr] = cl;
+		}
+
+		/* Remember current page to avoid unneeded page select */
+		err = ee1004_get_current_page();
+		if (err < 0)
+			goto err_clients;
+		dev_dbg(&client->dev, "Currently selected page: %d\n", err);
+		ee1004_current_page = err;
+	} else if (client->adapter != ee1004_set_page[0]->adapter) {
+		dev_err(&client->dev,
+			"Driver only supports devices on a single I2C bus\n");
+		err = -EOPNOTSUPP;
+		goto err_clients;
+	}
+	mutex_unlock(&ee1004_bus_lock);
+
+	dev_info(&client->dev,
+		 "%u byte EE1004-compliant SPD EEPROM, read-only\n",
+		 EE1004_EEPROM_SIZE);
+
+	return 0;
+
+ err_clients:
+	ee1004_cleanup(cnr);
+	mutex_unlock(&ee1004_bus_lock);
+
+	return err;
+}
+
+static void ee1004_remove(struct i2c_client *client)
+{
+	/* Remove page select clients if this is the last device */
+	mutex_lock(&ee1004_bus_lock);
+	ee1004_cleanup(EE1004_NUM_PAGES);
+	mutex_unlock(&ee1004_bus_lock);
+}
+
+/*-------------------------------------------------------------------------*/
+
+static struct i2c_driver ee1004_driver = {
+	.driver = {
+		.name = "ee1004",
+		.dev_groups = ee1004_groups,
+	},
+	.probe = ee1004_probe,
+	.remove = ee1004_remove,
+	.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");