[RFC,5/5] mfd: cros_ec: add EC host command support using rpmsg.

[Pi-Hsun Shih]

Add EC host command support through rpmsg.

Signed-off-by: Pi-Hsun Shih <pihsun@xxxxxxxxxxxx>
---
 drivers/mfd/cros_ec_dev.c               |   9 ++
 drivers/platform/chrome/Kconfig         |   8 ++
 drivers/platform/chrome/Makefile        |   1 +
 drivers/platform/chrome/cros_ec_rpmsg.c | 164 ++++++++++++++++++++++++
 include/linux/mfd/cros_ec.h             |   1 +
 include/linux/mfd/cros_ec_commands.h    |   2 +
 6 files changed, 185 insertions(+)
 create mode 100644 drivers/platform/chrome/cros_ec_rpmsg.c

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index 2d0fee488c5aa8..67983853413d07 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -414,6 +414,15 @@ static int ec_device_probe(struct platform_device *pdev)
 	device_initialize(&ec->class_dev);
 	cdev_init(&ec->cdev, &fops);
 
+	if (cros_ec_check_features(ec, EC_FEATURE_SCP)) {
+		dev_info(dev, "SCP detected.\n");
+		/*
+		 * Help userspace differentiating ECs from SCP,
+		 * regardless of the probing order.
+		 */
+		ec_platform->ec_name = CROS_EC_DEV_SCP_NAME;
+	}
+
 	/*
 	 * Add the class device
 	 * Link to the character device for creating the /dev entry
diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
index 16b1615958aa2d..b03d68eb732177 100644
--- a/drivers/platform/chrome/Kconfig
+++ b/drivers/platform/chrome/Kconfig
@@ -72,6 +72,14 @@ config CROS_EC_SPI
 	  response time cannot be guaranteed, we support ignoring
 	  'pre-amble' bytes before the response actually starts.
 
+config CROS_EC_RPMSG
+	tristate "ChromeOS Embedded Controller (rpmsg)"
+	depends on MFD_CROS_EC && RPMSG
+	help
+	  If you say Y here, you get support for talking to the ChromeOS EC
+	  through rpmsg. This uses a simple byte-level protocol with a
+	  checksum.
+
 config CROS_EC_LPC
         tristate "ChromeOS Embedded Controller (LPC)"
         depends on MFD_CROS_EC && ACPI && (X86 || COMPILE_TEST)
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index cd591bf872bbe9..3e3190af2b50f4 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -8,6 +8,7 @@ cros_ec_ctl-objs			:= cros_ec_sysfs.o cros_ec_lightbar.o \
 obj-$(CONFIG_CROS_EC_CTL)		+= cros_ec_ctl.o
 obj-$(CONFIG_CROS_EC_I2C)		+= cros_ec_i2c.o
 obj-$(CONFIG_CROS_EC_SPI)		+= cros_ec_spi.o
+obj-$(CONFIG_CROS_EC_RPMSG)		+= cros_ec_rpmsg.o
 cros_ec_lpcs-objs			:= cros_ec_lpc.o cros_ec_lpc_reg.o
 cros_ec_lpcs-$(CONFIG_CROS_EC_LPC_MEC)	+= cros_ec_lpc_mec.o
 obj-$(CONFIG_CROS_EC_LPC)		+= cros_ec_lpcs.o
diff --git a/drivers/platform/chrome/cros_ec_rpmsg.c b/drivers/platform/chrome/cros_ec_rpmsg.c
new file mode 100644
index 00000000000000..f123ca6d1c029c
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_rpmsg.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Copyright 2018 Google LLC.
+
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rpmsg.h>
+#include <linux/slab.h>
+
+/**
+ * cros_ec_cmd_xfer_rpmsg - Transfer a message over rpmsg and receive the reply
+ *
+ * This is only used for old EC proto version, and is not supported for this
+ * driver.
+ *
+ * @ec_dev: ChromeOS EC device
+ * @ec_msg: Message to transfer
+ */
+static int cros_ec_cmd_xfer_rpmsg(struct cros_ec_device *ec_dev,
+				  struct cros_ec_command *ec_msg)
+{
+	return -EINVAL;
+}
+
+/**
+ * cros_ec_pkt_xfer_rpmsg - Transfer a packet over rpmsg and receive the reply
+ *
+ * @ec_dev: ChromeOS EC device
+ * @ec_msg: Message to transfer
+ */
+static int cros_ec_pkt_xfer_rpmsg(struct cros_ec_device *ec_dev,
+				  struct cros_ec_command *ec_msg)
+{
+	struct ec_host_response *response;
+	struct rpmsg_device *rpdev = ec_dev->priv;
+	int len;
+	u8 sum;
+	int ret;
+	int i;
+
+	ec_msg->result = 0;
+	len = cros_ec_prepare_tx(ec_dev, ec_msg);
+	dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
+
+	// TODO: This currently relies on that mtk_rpmsg send actually blocks
+	// until ack. Should do the wait here instead.
+	ret = rpmsg_send(rpdev->ept, ec_dev->dout, len);
+
+	if (ret) {
+		dev_err(ec_dev->dev, "rpmsg send failed\n");
+		return ret;
+	}
+
+	/* check response error code */
+	response = (struct ec_host_response *)ec_dev->din;
+	ec_msg->result = response->result;
+
+	ret = cros_ec_check_result(ec_dev, ec_msg);
+	if (ret)
+		goto exit;
+
+	if (response->data_len > ec_msg->insize) {
+		dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
+			response->data_len, ec_msg->insize);
+		ret = -EMSGSIZE;
+		goto exit;
+	}
+
+	/* copy response packet payload and compute checksum */
+	memcpy(ec_msg->data, ec_dev->din + sizeof(*response),
+	       response->data_len);
+
+	sum = 0;
+	for (i = 0; i < sizeof(*response) + response->data_len; i++)
+		sum += ec_dev->din[i];
+
+	if (sum) {
+		dev_err(ec_dev->dev, "bad packet checksum, calculated %x\n",
+			sum);
+		ret = -EBADMSG;
+		goto exit;
+	}
+
+	ret = response->data_len;
+exit:
+	if (ec_msg->command == EC_CMD_REBOOT_EC)
+		msleep(EC_REBOOT_DELAY_MS);
+
+	return ret;
+}
+
+static int cros_ec_rpmsg_callback(struct rpmsg_device *rpdev, void *data,
+				  int len, void *priv, u32 src)
+{
+	struct cros_ec_device *ec_dev = dev_get_drvdata(&rpdev->dev);
+
+	if (len > ec_dev->din_size) {
+		dev_warn(ec_dev->dev,
+			 "ipi received length %d > din_size, truncating", len);
+		len = ec_dev->din_size;
+	}
+
+	memcpy(ec_dev->din, data, len);
+
+	return 0;
+}
+
+static int cros_ec_rpmsg_probe(struct rpmsg_device *rpdev)
+{
+	struct device *dev = &rpdev->dev;
+
+	struct cros_ec_device *ec_dev;
+	int ret;
+
+	ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
+	if (!ec_dev)
+		return -ENOMEM;
+
+	ec_dev->dev = dev;
+	ec_dev->priv = rpdev;
+	ec_dev->cmd_xfer = cros_ec_cmd_xfer_rpmsg;
+	ec_dev->pkt_xfer = cros_ec_pkt_xfer_rpmsg;
+	ec_dev->phys_name = dev_name(&rpdev->dev);
+	ec_dev->din_size = sizeof(struct ec_host_response) +
+			   sizeof(struct ec_response_get_protocol_info);
+	ec_dev->dout_size = sizeof(struct ec_host_request);
+	dev_set_drvdata(dev, ec_dev);
+
+	ret = cros_ec_register(ec_dev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void cros_ec_rpmsg_remove(struct rpmsg_device *rpdev)
+{
+	struct cros_ec_device *ec_dev = dev_get_drvdata(&rpdev->dev);
+
+	cros_ec_remove(ec_dev);
+}
+
+static const struct rpmsg_device_id cros_ec_rpmsg_device_id[] = {
+	{ .name = "cros-ec-rpmsg", },
+	{ /* sentinel */ },
+};
+
+static struct rpmsg_driver cros_ec_driver_rpmsg = {
+	.drv.name       = KBUILD_MODNAME,
+	.id_table       = cros_ec_rpmsg_device_id,
+	.probe		= cros_ec_rpmsg_probe,
+	.remove		= cros_ec_rpmsg_remove,
+	.callback	= cros_ec_rpmsg_callback,
+};
+
+module_rpmsg_driver(cros_ec_driver_rpmsg);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("ChromeOS EC multi function device (rpmsg)");
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index de8b588c8776da..fd297cf8f97295 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -24,6 +24,7 @@
 
 #define CROS_EC_DEV_NAME "cros_ec"
 #define CROS_EC_DEV_PD_NAME "cros_pd"
+#define CROS_EC_DEV_SCP_NAME "cros_scp"
 
 /*
  * The EC is unresponsive for a time after a reboot command.  Add a
diff --git a/include/linux/mfd/cros_ec_commands.h b/include/linux/mfd/cros_ec_commands.h
index fc91082d4c357b..3e5da6e93b2f42 100644
--- a/include/linux/mfd/cros_ec_commands.h
+++ b/include/linux/mfd/cros_ec_commands.h
@@ -856,6 +856,8 @@ enum ec_feature_code {
 	EC_FEATURE_RTC = 27,
 	/* EC supports CEC commands */
 	EC_FEATURE_CEC = 35,
+	/* The MCU exposes a SCP */
+	EC_FEATURE_SCP = 39,
 };
 
 #define EC_FEATURE_MASK_0(event_code) (1UL << (event_code % 32))
-- 
2.20.1.415.g653613c723-goog