platform/chrome: Add new driver for Wilco EC

This EC is an incompatible variant of the typical Chrome OS embedded
controller.  It uses the same low-level communication and a similar
protocol with some significant differences.  The EC firmware does
not support the same mailbox commands so it is not registered as a
cros_ec device type.  This commit exports the wilco_ec_mailbox()
function so that other modules can use it to communicate with the EC.

Signed-off-by: Duncan Laurie <dlaurie@google.com>
Signed-off-by: Nick Crews <ncrews@chromium.org>
[Fix the sparse warning: symbol 'wilco_ec_transfer' was not declared]
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
[Fix Kconfig dependencies for wilco_ec]
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

drivers/platform/chrome/Kconfig

@@ -152,4 +152,6 @@ config CROS_EC_SYSFS
 	  To compile this driver as a module, choose M here: the
 	  module will be called cros_ec_sysfs.
 
+source "drivers/platform/chrome/wilco_ec/Kconfig"
+
 endif # CHROMEOS_PLATFORMS

drivers/platform/chrome/Makefile

@@ -14,3 +14,5 @@ obj-$(CONFIG_CROS_EC_LIGHTBAR)		+= cros_ec_lightbar.o
 obj-$(CONFIG_CROS_EC_VBC)		+= cros_ec_vbc.o
 obj-$(CONFIG_CROS_EC_DEBUGFS)		+= cros_ec_debugfs.o
 obj-$(CONFIG_CROS_EC_SYSFS)		+= cros_ec_sysfs.o
+
+obj-$(CONFIG_WILCO_EC)			+= wilco_ec/

drivers/platform/chrome/wilco_ec/Kconfig

@@ -0,0 +1,10 @@
+config WILCO_EC
+	tristate "ChromeOS Wilco Embedded Controller"
+	depends on ACPI && X86 && CROS_EC_LPC_MEC
+	help
+	  If you say Y here, you get support for talking to the ChromeOS
+	  Wilco EC over an eSPI bus. This uses a simple byte-level protocol
+	  with a checksum.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called wilco_ec.

drivers/platform/chrome/wilco_ec/Makefile

@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+
+wilco_ec-objs				:= core.o mailbox.o
+obj-$(CONFIG_WILCO_EC)			+= wilco_ec.o

drivers/platform/chrome/wilco_ec/core.c

@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Core driver for Wilco Embedded Controller
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This is the entry point for the drivers that control the Wilco EC.
+ * This driver is responsible for several tasks:
+ * - Initialize the register interface that is used by wilco_ec_mailbox()
+ * - Create a platform device which is picked up by the debugfs driver
+ * - Create a platform device which is picked up by the RTC driver
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/platform_data/wilco-ec.h>
+#include <linux/platform_device.h>
+
+#include "../cros_ec_lpc_mec.h"
+
+#define DRV_NAME "wilco-ec"
+
+static struct resource *wilco_get_resource(struct platform_device *pdev,
+					   int index)
+{
+	struct device *dev = &pdev->dev;
+	struct resource *res;
+
+	res = platform_get_resource(pdev, IORESOURCE_IO, index);
+	if (!res) {
+		dev_dbg(dev, "Couldn't find IO resource %d\n", index);
+		return res;
+	}
+
+	return devm_request_region(dev, res->start, resource_size(res),
+				   dev_name(dev));
+}
+
+static int wilco_ec_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct wilco_ec_device *ec;
+
+	ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
+	if (!ec)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, ec);
+	ec->dev = dev;
+	mutex_init(&ec->mailbox_lock);
+
+	/* Largest data buffer size requirement is extended data response */
+	ec->data_size = sizeof(struct wilco_ec_response) +
+		EC_MAILBOX_DATA_SIZE_EXTENDED;
+	ec->data_buffer = devm_kzalloc(dev, ec->data_size, GFP_KERNEL);
+	if (!ec->data_buffer)
+		return -ENOMEM;
+
+	/* Prepare access to IO regions provided by ACPI */
+	ec->io_data = wilco_get_resource(pdev, 0);	/* Host Data */
+	ec->io_command = wilco_get_resource(pdev, 1);	/* Host Command */
+	ec->io_packet = wilco_get_resource(pdev, 2);	/* MEC EMI */
+	if (!ec->io_data || !ec->io_command || !ec->io_packet)
+		return -ENODEV;
+
+	/* Initialize cros_ec register interface for communication */
+	cros_ec_lpc_mec_init(ec->io_packet->start,
+			     ec->io_packet->start + EC_MAILBOX_DATA_SIZE);
+
+	return 0;
+}
+
+static int wilco_ec_remove(struct platform_device *pdev)
+{
+	/* Teardown cros_ec interface */
+	cros_ec_lpc_mec_destroy();
+
+	return 0;
+}
+
+static const struct acpi_device_id wilco_ec_acpi_device_ids[] = {
+	{ "GOOG000C", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, wilco_ec_acpi_device_ids);
+
+static struct platform_driver wilco_ec_driver = {
+	.driver = {
+		.name = DRV_NAME,
+		.acpi_match_table = wilco_ec_acpi_device_ids,
+	},
+	.probe = wilco_ec_probe,
+	.remove = wilco_ec_remove,
+};
+
+module_platform_driver(wilco_ec_driver);
+
+MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
+MODULE_AUTHOR("Duncan Laurie <dlaurie@chromium.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS Wilco Embedded Controller driver");
+MODULE_ALIAS("platform:" DRV_NAME);

drivers/platform/chrome/wilco_ec/mailbox.c

@@ -0,0 +1,237 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Mailbox interface for Wilco Embedded Controller
+ *
+ * Copyright 2018 Google LLC
+ *
+ * The Wilco EC is similar to a typical ChromeOS embedded controller.
+ * It uses the same MEC based low-level communication and a similar
+ * protocol, but with some important differences.  The EC firmware does
+ * not support the same mailbox commands so it is not registered as a
+ * cros_ec device type.
+ *
+ * Most messages follow a standard format, but there are some exceptions
+ * and an interface is provided to do direct/raw transactions that do not
+ * make assumptions about byte placement.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/platform_data/wilco-ec.h>
+#include <linux/platform_device.h>
+
+#include "../cros_ec_lpc_mec.h"
+
+/* Version of mailbox interface */
+#define EC_MAILBOX_VERSION		0
+
+/* Command to start mailbox transaction */
+#define EC_MAILBOX_START_COMMAND	0xda
+
+/* Version of EC protocol */
+#define EC_MAILBOX_PROTO_VERSION	3
+
+/* Number of header bytes to be counted as data bytes */
+#define EC_MAILBOX_DATA_EXTRA		2
+
+/* Maximum timeout */
+#define EC_MAILBOX_TIMEOUT		HZ
+
+/* EC response flags */
+#define EC_CMDR_DATA		BIT(0)	/* Data ready for host to read */
+#define EC_CMDR_PENDING		BIT(1)	/* Write pending to EC */
+#define EC_CMDR_BUSY		BIT(2)	/* EC is busy processing a command */
+#define EC_CMDR_CMD		BIT(3)	/* Last host write was a command */
+
+/**
+ * wilco_ec_response_timed_out() - Wait for EC response.
+ * @ec: EC device.
+ *
+ * Return: true if EC timed out, false if EC did not time out.
+ */
+static bool wilco_ec_response_timed_out(struct wilco_ec_device *ec)
+{
+	unsigned long timeout = jiffies + EC_MAILBOX_TIMEOUT;
+
+	do {
+		if (!(inb(ec->io_command->start) &
+		      (EC_CMDR_PENDING | EC_CMDR_BUSY)))
+			return false;
+		usleep_range(100, 200);
+	} while (time_before(jiffies, timeout));
+
+	return true;
+}
+
+/**
+ * wilco_ec_checksum() - Compute 8-bit checksum over data range.
+ * @data: Data to checksum.
+ * @size: Number of bytes to checksum.
+ *
+ * Return: 8-bit checksum of provided data.
+ */
+static u8 wilco_ec_checksum(const void *data, size_t size)
+{
+	u8 *data_bytes = (u8 *)data;
+	u8 checksum = 0;
+	size_t i;
+
+	for (i = 0; i < size; i++)
+		checksum += data_bytes[i];
+
+	return checksum;
+}
+
+/**
+ * wilco_ec_prepare() - Prepare the request structure for the EC.
+ * @msg: EC message with request information.
+ * @rq: EC request structure to fill.
+ */
+static void wilco_ec_prepare(struct wilco_ec_message *msg,
+			     struct wilco_ec_request *rq)
+{
+	memset(rq, 0, sizeof(*rq));
+
+	/* Handle messages without trimming bytes from the request */
+	if (msg->request_size && msg->flags & WILCO_EC_FLAG_RAW_REQUEST) {
+		rq->reserved_raw = *(u8 *)msg->request_data;
+		msg->request_size--;
+		memmove(msg->request_data, msg->request_data + 1,
+			msg->request_size);
+	}
+
+	/* Fill in request packet */
+	rq->struct_version = EC_MAILBOX_PROTO_VERSION;
+	rq->mailbox_id = msg->type;
+	rq->mailbox_version = EC_MAILBOX_VERSION;
+	rq->data_size = msg->request_size + EC_MAILBOX_DATA_EXTRA;
+	rq->command = msg->command;
+
+	/* Checksum header and data */
+	rq->checksum = wilco_ec_checksum(rq, sizeof(*rq));
+	rq->checksum += wilco_ec_checksum(msg->request_data, msg->request_size);
+	rq->checksum = -rq->checksum;
+}
+
+/**
+ * wilco_ec_transfer() - Perform actual data transfer.
+ * @ec: EC device.
+ * @msg: EC message data for request and response.
+ * @rq: Filled in request structure
+ *
+ * Context: ec->mailbox_lock should be held while using this function.
+ * Return: number of bytes received or negative error code on failure.
+ */
+static int wilco_ec_transfer(struct wilco_ec_device *ec,
+			     struct wilco_ec_message *msg,
+			     struct wilco_ec_request *rq)
+{
+	struct wilco_ec_response *rs;
+	u8 checksum;
+	u8 flag;
+	size_t size;
+
+	/* Write request header, then data */
+	cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq);
+	cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size,
+				 msg->request_data);
+
+	/* Start the command */
+	outb(EC_MAILBOX_START_COMMAND, ec->io_command->start);
+
+	/* For some commands (eg shutdown) the EC will not respond, that's OK */
+	if (msg->flags & WILCO_EC_FLAG_NO_RESPONSE) {
+		dev_dbg(ec->dev, "EC does not respond to this command\n");
+		return 0;
+	}
+
+	/* Wait for it to complete */
+	if (wilco_ec_response_timed_out(ec)) {
+		dev_dbg(ec->dev, "response timed out\n");
+		return -ETIMEDOUT;
+	}
+
+	/* Check result */
+	flag = inb(ec->io_data->start);
+	if (flag) {
+		dev_dbg(ec->dev, "bad response: 0x%02x\n", flag);
+		return -EIO;
+	}
+
+	if (msg->flags & WILCO_EC_FLAG_EXTENDED_DATA)
+		size = EC_MAILBOX_DATA_SIZE_EXTENDED;
+	else
+		size = EC_MAILBOX_DATA_SIZE;
+
+	/* Read back response */
+	rs = ec->data_buffer;
+	checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0,
+					    sizeof(*rs) + size, (u8 *)rs);
+	if (checksum) {
+		dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum);
+		return -EBADMSG;
+	}
+
+	/* Check that the EC reported success */
+	msg->result = rs->result;
+	if (msg->result) {
+		dev_dbg(ec->dev, "bad response: 0x%02x\n", msg->result);
+		return -EBADMSG;
+	}
+
+	/* Check the returned data size, skipping the header */
+	if (rs->data_size != size) {
+		dev_dbg(ec->dev, "unexpected packet size (%u != %zu)",
+			rs->data_size, size);
+		return -EMSGSIZE;
+	}
+
+	/* Skip 1 response data byte unless specified */
+	size = (msg->flags & WILCO_EC_FLAG_RAW_RESPONSE) ? 0 : 1;
+	if ((ssize_t) rs->data_size - size < msg->response_size) {
+		dev_dbg(ec->dev, "response data too short (%zd < %zu)",
+			(ssize_t) rs->data_size - size, msg->response_size);
+		return -EMSGSIZE;
+	}
+
+	/* Ignore response data bytes as requested */
+	memcpy(msg->response_data, rs->data + size, msg->response_size);
+
+	/* Return actual amount of data received */
+	return msg->response_size;
+}
+
+/**
+ * wilco_ec_mailbox() - Send EC request and receive EC response.
+ * @ec: EC device.
+ * @msg: EC message data for request and response.
+ *
+ * On entry msg->type, msg->flags, msg->command, msg->request_size,
+ * msg->response_size, and msg->request_data should all be filled in.
+ *
+ * On exit msg->result and msg->response_data will be filled.
+ *
+ * Return: number of bytes received or negative error code on failure.
+ */
+int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg)
+{
+	struct wilco_ec_request *rq;
+	int ret;
+
+	dev_dbg(ec->dev, "cmd=%02x type=%04x flags=%02x rslen=%zu rqlen=%zu\n",
+		msg->command, msg->type, msg->flags, msg->response_size,
+		msg->request_size);
+
+	/* Prepare request packet */
+	rq = ec->data_buffer;
+	wilco_ec_prepare(msg, rq);
+
+	mutex_lock(&ec->mailbox_lock);
+	ret = wilco_ec_transfer(ec, msg, rq);
+	mutex_unlock(&ec->mailbox_lock);
+
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(wilco_ec_mailbox);