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Subject[PATCH 3/5] mfd: Add ChromeOS EC I2C driver
Date
This uses an I2C bus to talk to the ChromeOS EC. The protocol
is defined by the EC and is fairly simple, with a length byte,
checksum, command byte and version byte (to permit easy creation
of new commands).

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
---
drivers/mfd/Kconfig | 10 ++
drivers/mfd/Makefile | 1 +
drivers/mfd/cros_ec_i2c.c | 262 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 273 insertions(+), 0 deletions(-)
create mode 100644 drivers/mfd/cros_ec_i2c.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 6983eb4..9351614 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -29,6 +29,16 @@ config MFD_CROS_EC
You also ned to enable the driver for the bus you are using. The
protocol for talking to the EC is defined by the bus driver.

+config MFD_CROS_EC_I2C
+ tristate "ChromeOS Embedded Controller (I2C)"
+ depends on MFD_CROS_EC && I2C
+
+ help
+ If you say here, you get support for talking to the ChromeOS EC
+ through an I2C bus. This uses a simple byte-level protocol with
+ a checksum. Failing accesses will be retried three times to
+ improve reliability.
+
config MFD_88PM800
tristate "Support Marvell 88PM800"
depends on I2C=y && GENERIC_HARDIRQS
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 5a9c9f6..603912e 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_MFD_88PM805) += 88pm805.o 88pm80x.o
obj-$(CONFIG_MFD_SM501) += sm501.o
obj-$(CONFIG_MFD_ASIC3) += asic3.o tmio_core.o
obj-$(CONFIG_MFD_CROS_EC) += cros_ec.o
+obj-$(CONFIG_MFD_CROS_EC_I2C) += cros_ec_i2c.o

rtsx_pci-objs := rtsx_pcr.o rts5209.o rts5229.o rtl8411.o
obj-$(CONFIG_MFD_RTSX_PCI) += rtsx_pci.o
diff --git a/drivers/mfd/cros_ec_i2c.c b/drivers/mfd/cros_ec_i2c.c
new file mode 100644
index 0000000..6b112ad
--- /dev/null
+++ b/drivers/mfd/cros_ec_i2c.c
@@ -0,0 +1,262 @@
+/*
+ * ChromeOS EC multi-function device (I2C)
+ *
+ * Copyright (C) 2012 Google, Inc
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+
+/* Since I2C can be unreliable, we retry commands */
+#define COMMAND_MAX_TRIES 3
+
+static inline struct cros_ec_device *to_ec_dev(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+
+ return i2c_get_clientdata(client);
+}
+
+static int cros_ec_command_xfer_noretry(struct cros_ec_device *ec_dev,
+ struct cros_ec_msg *msg)
+{
+ struct i2c_client *client = ec_dev->priv;
+ int ret = -ENOMEM;
+ int i;
+ int packet_len;
+ u8 *out_buf = NULL;
+ u8 *in_buf = NULL;
+ u8 sum;
+ struct i2c_msg i2c_msg[2];
+
+ i2c_msg[0].addr = client->addr;
+ i2c_msg[0].flags = 0;
+ i2c_msg[1].addr = client->addr;
+ i2c_msg[1].flags = I2C_M_RD;
+
+ /*
+ * allocate larger packet (one byte for checksum, one byte for
+ * length, and one for result code)
+ */
+ packet_len = msg->in_len + 3;
+ in_buf = kzalloc(packet_len, GFP_KERNEL);
+ if (!in_buf)
+ goto done;
+ i2c_msg[1].len = packet_len;
+ i2c_msg[1].buf = (char *)in_buf;
+
+ /*
+ * allocate larger packet (one byte for checksum, one for
+ * command code, one for length, and one for command version)
+ */
+ packet_len = msg->out_len + 4;
+ out_buf = kzalloc(packet_len, GFP_KERNEL);
+ if (!out_buf)
+ goto done;
+ i2c_msg[0].len = packet_len;
+ i2c_msg[0].buf = (char *)out_buf;
+
+ out_buf[0] = EC_CMD_VERSION0 + msg->version;
+ out_buf[1] = msg->cmd;
+ out_buf[2] = msg->out_len;
+
+ /* copy message payload and compute checksum */
+ sum = out_buf[0] + out_buf[1] + out_buf[2];
+ for (i = 0; i < msg->out_len; i++) {
+ out_buf[3 + i] = msg->out_buf[i];
+ sum += out_buf[3 + i];
+ }
+ out_buf[3 + msg->out_len] = sum;
+
+ /* send command to EC and read answer */
+ ret = i2c_transfer(client->adapter, i2c_msg, 2);
+ if (ret < 0) {
+ dev_err(ec_dev->dev, "i2c transfer failed: %d\n", ret);
+ goto done;
+ } else if (ret != 2) {
+ dev_err(ec_dev->dev, "failed to get response: %d\n", ret);
+ ret = -EIO;
+ goto done;
+ }
+
+ /* check response error code */
+ if (i2c_msg[1].buf[0]) {
+ dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n",
+ msg->cmd, i2c_msg[1].buf[0]);
+ ret = -EINVAL;
+ goto done;
+ }
+
+ /* copy response packet payload and compute checksum */
+ sum = in_buf[0] + in_buf[1];
+ for (i = 0; i < msg->in_len; i++) {
+ msg->in_buf[i] = in_buf[2 + i];
+ sum += in_buf[2 + i];
+ }
+#ifdef DEBUG
+ dev_dbg(ec_dev->dev, "packet: ");
+ for (i = 0; i < i2c_msg[1].len; i++)
+ dev_cont(ec_dev->dev, " %02x", in_buf[i]);
+ dev_cont(ec_dev->dev, ", sum = %02x\n", sum);
+#endif
+ if (sum != in_buf[2 + msg->in_len]) {
+ dev_err(ec_dev->dev, "bad packet checksum\n");
+ ret = -EBADMSG;
+ goto done;
+ }
+
+ ret = 0;
+ done:
+ kfree(in_buf);
+ kfree(out_buf);
+ return ret;
+}
+
+static int cros_ec_command_xfer(struct cros_ec_device *ec_dev,
+ struct cros_ec_msg *msg)
+{
+ int tries;
+ int ret;
+ /*
+ * Try the command a few times in case there are transmission errors.
+ * It is possible that this is overkill, but we don't completely trust
+ * i2c.
+ */
+ for (tries = 0; tries < COMMAND_MAX_TRIES; tries++) {
+ ret = cros_ec_command_xfer_noretry(ec_dev, msg);
+ if (ret >= 0)
+ return ret;
+ }
+ dev_err(ec_dev->dev, "ec_command failed with %d (%d tries)\n",
+ ret, tries);
+ return ret;
+}
+
+static const char *cros_ec_get_name(struct cros_ec_device *ec_dev)
+{
+ struct i2c_client *client = ec_dev->priv;
+
+ return client->name;
+}
+
+static const char *cros_ec_get_phys_name(struct cros_ec_device *ec_dev)
+{
+ struct i2c_client *client = ec_dev->priv;
+
+ return client->adapter->name;
+}
+
+static struct device *cros_ec_get_parent(struct cros_ec_device *ec_dev)
+{
+ struct i2c_client *client = ec_dev->priv;
+
+ return &client->dev;
+}
+
+static int __devinit cros_ec_probe_i2c(struct i2c_client *client,
+ const struct i2c_device_id *dev_id)
+{
+ struct device *dev = &client->dev;
+ struct cros_ec_device *ec_dev = NULL;
+ int err;
+
+ if (dev->of_node && !of_device_is_available(dev->of_node)) {
+ dev_warn(dev, "Device disabled by device tree\n");
+ return -ENODEV;
+ }
+
+ ec_dev = cros_ec_alloc("I2C");
+ if (!ec_dev) {
+ err = -ENOMEM;
+ dev_err(dev, "cannot create cros_ec\n");
+ goto fail;
+ }
+
+ i2c_set_clientdata(client, ec_dev);
+ ec_dev->dev = dev;
+ ec_dev->priv = client;
+ ec_dev->irq = client->irq;
+ ec_dev->command_xfer = cros_ec_command_xfer;
+ ec_dev->get_name = cros_ec_get_name;
+ ec_dev->get_phys_name = cros_ec_get_phys_name;
+ ec_dev->get_parent = cros_ec_get_parent;
+
+ err = cros_ec_register(ec_dev);
+ if (err) {
+ dev_err(dev, "cannot register EC\n");
+ goto fail_register;
+ }
+
+ return 0;
+fail_register:
+ cros_ec_free(ec_dev);
+fail:
+ return err;
+}
+
+static int __devexit cros_ec_remove_i2c(struct i2c_client *client)
+{
+ struct cros_ec_device *ec_dev = i2c_get_clientdata(client);
+
+ cros_ec_remove(ec_dev);
+ cros_ec_free(ec_dev);
+
+ return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int cros_ec_i2c_suspend(struct device *dev)
+{
+ struct cros_ec_device *ec_dev = to_ec_dev(dev);
+
+ return cros_ec_suspend(ec_dev);
+}
+
+static int cros_ec_i2c_resume(struct device *dev)
+{
+ struct cros_ec_device *ec_dev = to_ec_dev(dev);
+
+ return cros_ec_resume(ec_dev);
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(cros_ec_i2c_pm_ops, cros_ec_i2c_suspend,
+ cros_ec_i2c_resume);
+
+static const struct i2c_device_id cros_ec_i2c_id[] = {
+ { "cros-ec-i2c", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, cros_ec_i2c_id);
+
+static struct i2c_driver cros_ec_driver = {
+ .driver = {
+ .name = "cros-ec-i2c",
+ .owner = THIS_MODULE,
+ .pm = &cros_ec_i2c_pm_ops,
+ },
+ .probe = cros_ec_probe_i2c,
+ .remove = cros_ec_remove_i2c,
+ .id_table = cros_ec_i2c_id,
+};
+
+module_i2c_driver(cros_ec_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ChromeOS EC multi function device");
--
1.7.7.3


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