platform/chrome: Add cros_ec_lpc driver for x86 devices

Chromebooks have an Embedded Controller (EC) that is used to
implement various functions such as keyboard, power and battery.

The AP can communicate with the EC through different bus types
such as I2C, SPI or LPC.

The cros_ec mfd driver is then composed of a core driver that
register the sub-devices as mfd cells and provide a high level
communication interface that is used by the rest of the kernel
and bus specific interfaces modules.

Each connection method then has its own driver, which register
with the EC driver interface-agnostic interface.

Currently, there are drivers to communicate with the EC over
I2C and SPI and this driver adds support for LPC.

Signed-off-by: Bill Richardson <[e-mail]>
Signed-off-by: Javier Martinez Canillas <[e-mail]>
Tested-by: Gwendal Grignou <[e-mail]>
Reviewed-by: Gwendal Grignou <[e-mail]>
Signed-off-by: Olof Johansson <[e-mail]>

drivers/platform/chrome/Kconfig

···
 	  The module will be called chromeos_pstore.
 
 
+config CROS_EC_LPC
+        tristate "ChromeOS Embedded Controller (LPC)"
+        depends on MFD_CROS_EC
+        help
+          If you say Y here, you get support for talking to the ChromeOS EC
+          over an LPC bus. This uses a simple byte-level protocol with a
+          checksum. This is used for userspace access only. The kernel
+          typically has its own communication methods.
+
+          To compile this driver as a module, choose M here: the
+          module will be called cros_ec_lpc.
+
 endif # CHROMEOS_PLATFORMS

drivers/platform/chrome/Makefile

···
 
 obj-$(CONFIG_CHROMEOS_LAPTOP)	+= chromeos_laptop.o
 obj-$(CONFIG_CHROMEOS_PSTORE)	+= chromeos_pstore.o
+obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o

drivers/platform/chrome/cros_ec_lpc.c

···
+/*
+ * cros_ec_lpc - LPC access to the Chrome OS Embedded Controller
+ *
+ * Copyright (C) 2012-2015 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.
+ *
+ * This driver uses the Chrome OS EC byte-level message-based protocol for
+ * communicating the keyboard state (which keys are pressed) from a keyboard EC
+ * to the AP over some bus (such as i2c, lpc, spi).  The EC does debouncing,
+ * but everything else (including deghosting) is done here.  The main
+ * motivation for this is to keep the EC firmware as simple as possible, since
+ * it cannot be easily upgraded and EC flash/IRAM space is relatively
+ * expensive.
+ */
+
+#include <linux/dmi.h>
+#include <linux/delay.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+
+#define DRV_NAME "cros_ec_lpc"
+
+static int ec_response_timed_out(void)
+{
+	unsigned long one_second = jiffies + HZ;
+
+	usleep_range(200, 300);
+	do {
+		if (!(inb(EC_LPC_ADDR_HOST_CMD) & EC_LPC_STATUS_BUSY_MASK))
+			return 0;
+		usleep_range(100, 200);
+	} while (time_before(jiffies, one_second));
+
+	return 1;
+}
+
+static int cros_ec_cmd_xfer_lpc(struct cros_ec_device *ec,
+				struct cros_ec_command *msg)
+{
+	struct ec_lpc_host_args args;
+	int csum;
+	int i;
+	int ret = 0;
+
+	if (msg->outsize > EC_PROTO2_MAX_PARAM_SIZE ||
+	    msg->insize > EC_PROTO2_MAX_PARAM_SIZE) {
+		dev_err(ec->dev,
+			"invalid buffer sizes (out %d, in %d)\n",
+			msg->outsize, msg->insize);
+		return -EINVAL;
+	}
+
+	/* Now actually send the command to the EC and get the result */
+	args.flags = EC_HOST_ARGS_FLAG_FROM_HOST;
+	args.command_version = msg->version;
+	args.data_size = msg->outsize;
+
+	/* Initialize checksum */
+	csum = msg->command + args.flags +
+		args.command_version + args.data_size;
+
+	/* Copy data and update checksum */
+	for (i = 0; i < msg->outsize; i++) {
+		outb(msg->outdata[i], EC_LPC_ADDR_HOST_PARAM + i);
+		csum += msg->outdata[i];
+	}
+
+	/* Finalize checksum and write args */
+	args.checksum = csum & 0xFF;
+	outb(args.flags, EC_LPC_ADDR_HOST_ARGS);
+	outb(args.command_version, EC_LPC_ADDR_HOST_ARGS + 1);
+	outb(args.data_size, EC_LPC_ADDR_HOST_ARGS + 2);
+	outb(args.checksum, EC_LPC_ADDR_HOST_ARGS + 3);
+
+	/* Here we go */
+	outb(msg->command, EC_LPC_ADDR_HOST_CMD);
+
+	if (ec_response_timed_out()) {
+		dev_warn(ec->dev, "EC responsed timed out\n");
+		ret = -EIO;
+		goto done;
+	}
+
+	/* Check result */
+	msg->result = inb(EC_LPC_ADDR_HOST_DATA);
+
+	switch (msg->result) {
+	case EC_RES_SUCCESS:
+		break;
+	case EC_RES_IN_PROGRESS:
+		ret = -EAGAIN;
+		dev_dbg(ec->dev, "command 0x%02x in progress\n",
+			msg->command);
+		goto done;
+	default:
+		dev_dbg(ec->dev, "command 0x%02x returned %d\n",
+			msg->command, msg->result);
+	}
+
+	/* Read back args */
+	args.flags = inb(EC_LPC_ADDR_HOST_ARGS);
+	args.command_version = inb(EC_LPC_ADDR_HOST_ARGS + 1);
+	args.data_size = inb(EC_LPC_ADDR_HOST_ARGS + 2);
+	args.checksum = inb(EC_LPC_ADDR_HOST_ARGS + 3);
+
+	if (args.data_size > msg->insize) {
+		dev_err(ec->dev,
+			"packet too long (%d bytes, expected %d)",
+			args.data_size, msg->insize);
+		ret = -ENOSPC;
+		goto done;
+	}
+
+	/* Start calculating response checksum */
+	csum = msg->command + args.flags +
+		args.command_version + args.data_size;
+
+	/* Read response and update checksum */
+	for (i = 0; i < args.data_size; i++) {
+		msg->indata[i] = inb(EC_LPC_ADDR_HOST_PARAM + i);
+		csum += msg->indata[i];
+	}
+
+	/* Verify checksum */
+	if (args.checksum != (csum & 0xFF)) {
+		dev_err(ec->dev,
+			"bad packet checksum, expected %02x, got %02x\n",
+			args.checksum, csum & 0xFF);
+		ret = -EBADMSG;
+		goto done;
+	}
+
+	/* Return actual amount of data received */
+	ret = args.data_size;
+done:
+	return ret;
+}
+
+/* Returns num bytes read, or negative on error. Doesn't need locking. */
+static int cros_ec_lpc_readmem(struct cros_ec_device *ec, unsigned int offset,
+			       unsigned int bytes, void *dest)
+{
+	int i = offset;
+	char *s = dest;
+	int cnt = 0;
+
+	if (offset >= EC_MEMMAP_SIZE - bytes)
+		return -EINVAL;
+
+	/* fixed length */
+	if (bytes) {
+		for (; cnt < bytes; i++, s++, cnt++)
+			*s = inb(EC_LPC_ADDR_MEMMAP + i);
+		return cnt;
+	}
+
+	/* string */
+	for (; i < EC_MEMMAP_SIZE; i++, s++) {
+		*s = inb(EC_LPC_ADDR_MEMMAP + i);
+		cnt++;
+		if (!*s)
+			break;
+	}
+
+	return cnt;
+}
+
+static int cros_ec_lpc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_device *ec_dev;
+	int ret;
+
+	if (!devm_request_region(dev, EC_LPC_ADDR_MEMMAP, EC_MEMMAP_SIZE,
+				 dev_name(dev))) {
+		dev_err(dev, "couldn't reserve memmap region\n");
+		return -EBUSY;
+	}
+
+	if ((inb(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID) != 'E') ||
+	    (inb(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID + 1) != 'C')) {
+		dev_err(dev, "EC ID not detected\n");
+		return -ENODEV;
+	}
+
+	if (!devm_request_region(dev, EC_HOST_CMD_REGION0,
+				 EC_HOST_CMD_REGION_SIZE, dev_name(dev))) {
+		dev_err(dev, "couldn't reserve region0\n");
+		return -EBUSY;
+	}
+	if (!devm_request_region(dev, EC_HOST_CMD_REGION1,
+				 EC_HOST_CMD_REGION_SIZE, dev_name(dev))) {
+		dev_err(dev, "couldn't reserve region1\n");
+		return -EBUSY;
+	}
+
+	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
+	if (!ec_dev)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, ec_dev);
+	ec_dev->dev = dev;
+	ec_dev->ec_name = pdev->name;
+	ec_dev->phys_name = dev_name(dev);
+	ec_dev->parent = dev;
+	ec_dev->cmd_xfer = cros_ec_cmd_xfer_lpc;
+	ec_dev->cmd_readmem = cros_ec_lpc_readmem;
+
+	ret = cros_ec_register(ec_dev);
+	if (ret) {
+		dev_err(dev, "couldn't register ec_dev (%d)\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int cros_ec_lpc_remove(struct platform_device *pdev)
+{
+	struct cros_ec_device *ec_dev;
+
+	ec_dev = platform_get_drvdata(pdev);
+	cros_ec_remove(ec_dev);
+
+	return 0;
+}
+
+static struct dmi_system_id cros_ec_lpc_dmi_table[] __initdata = {
+	{
+		/*
+		 * Today all Chromebooks/boxes ship with Google_* as version and
+		 * coreboot as bios vendor. No other systems with this
+		 * combination are known to date.
+		 */
+		.matches = {
+			DMI_MATCH(DMI_BIOS_VENDOR, "coreboot"),
+			DMI_MATCH(DMI_BIOS_VERSION, "Google_"),
+		},
+	},
+	{
+		/* x86-link, the Chromebook Pixel. */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "GOOGLE"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Link"),
+		},
+	},
+	{
+		/* x86-peppy, the Acer C720 Chromebook. */
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Peppy"),
+		},
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(dmi, cros_ec_lpc_dmi_table);
+
+static struct platform_driver cros_ec_lpc_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.owner = THIS_MODULE,
+	},
+	.probe = cros_ec_lpc_probe,
+	.remove = cros_ec_lpc_remove,
+};
+
+static struct platform_device cros_ec_lpc_device = {
+	.name = DRV_NAME
+};
+
+static int __init cros_ec_lpc_init(void)
+{
+	int ret;
+
+	if (!dmi_check_system(cros_ec_lpc_dmi_table)) {
+		pr_err(DRV_NAME ": unsupported system.\n");
+		return -ENODEV;
+	}
+
+	/* Register the driver */
+	ret = platform_driver_register(&cros_ec_lpc_driver);
+	if (ret) {
+		pr_err(DRV_NAME ": can't register driver: %d\n", ret);
+		return ret;
+	}
+
+	/* Register the device, and it'll get hooked up automatically */
+	ret = platform_device_register(&cros_ec_lpc_device);
+	if (ret) {
+		pr_err(DRV_NAME ": can't register device: %d\n", ret);
+		platform_driver_unregister(&cros_ec_lpc_driver);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit cros_ec_lpc_exit(void)
+{
+	platform_device_unregister(&cros_ec_lpc_device);
+	platform_driver_unregister(&cros_ec_lpc_driver);
+}
+
+module_init(cros_ec_lpc_init);
+module_exit(cros_ec_lpc_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ChromeOS EC LPC driver");