[PATCH v11 2/2] usb: typec: ucsi: Implement ChromeOS UCSI driver

["Łukasz Bartosik" <ukaszb@chromium.org>]

From: Pavan Holla <pholla@chromium.org>

Implementation of a UCSI transport driver for ChromeOS.
This driver will be loaded if the ChromeOS EC implements a PPM.

Signed-off-by: Pavan Holla <pholla@chromium.org>
Co-developed-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Co-developed-by: Łukasz Bartosik <ukaszb@chromium.org>
Signed-off-by: Łukasz Bartosik <ukaszb@chromium.org>
---
 MAINTAINERS                           |   7 +
 drivers/usb/typec/ucsi/Kconfig        |  13 +
 drivers/usb/typec/ucsi/Makefile       |   1 +
 drivers/usb/typec/ucsi/cros_ec_ucsi.c | 337 ++++++++++++++++++++++++++
 4 files changed, 358 insertions(+)
 create mode 100644 drivers/usb/typec/ucsi/cros_ec_ucsi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 17daa9ee9384..6d24db48421d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5454,6 +5454,13 @@ L:	chrome-platform@lists.linux.dev
 S:	Maintained
 F:	drivers/watchdog/cros_ec_wdt.c
 
+CHROMEOS UCSI DRIVER
+M:	Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
+M:	Łukasz Bartosik <ukaszb@chromium.org>
+L:	chrome-platform@lists.linux.dev
+S:	Maintained
+F:	drivers/usb/typec/ucsi/cros_ec_ucsi.c
+
 CHRONTEL CH7322 CEC DRIVER
 M:	Joe Tessler <jrt@google.com>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/usb/typec/ucsi/Kconfig b/drivers/usb/typec/ucsi/Kconfig
index 680e1b87b152..75559601fe8f 100644
--- a/drivers/usb/typec/ucsi/Kconfig
+++ b/drivers/usb/typec/ucsi/Kconfig
@@ -69,6 +69,19 @@ config UCSI_PMIC_GLINK
 	  To compile the driver as a module, choose M here: the module will be
 	  called ucsi_glink.
 
+config CROS_EC_UCSI
+	tristate "UCSI Driver for ChromeOS EC"
+	depends on MFD_CROS_EC_DEV
+	depends on CROS_USBPD_NOTIFY
+	depends on !EXTCON_TCSS_CROS_EC
+	default MFD_CROS_EC_DEV
+	help
+	  This driver enables UCSI support for a ChromeOS EC. The EC is
+	  expected to implement a PPM.
+
+	  To compile the driver as a module, choose M here: the module
+	  will be called cros_ec_ucsi.
+
 config UCSI_LENOVO_YOGA_C630
 	tristate "UCSI Interface Driver for Lenovo Yoga C630"
 	depends on EC_LENOVO_YOGA_C630
diff --git a/drivers/usb/typec/ucsi/Makefile b/drivers/usb/typec/ucsi/Makefile
index aed41d23887b..be98a879104d 100644
--- a/drivers/usb/typec/ucsi/Makefile
+++ b/drivers/usb/typec/ucsi/Makefile
@@ -21,4 +21,5 @@ obj-$(CONFIG_UCSI_ACPI)			+= ucsi_acpi.o
 obj-$(CONFIG_UCSI_CCG)			+= ucsi_ccg.o
 obj-$(CONFIG_UCSI_STM32G0)		+= ucsi_stm32g0.o
 obj-$(CONFIG_UCSI_PMIC_GLINK)		+= ucsi_glink.o
+obj-$(CONFIG_CROS_EC_UCSI)		+= cros_ec_ucsi.o
 obj-$(CONFIG_UCSI_LENOVO_YOGA_C630)	+= ucsi_yoga_c630.o
diff --git a/drivers/usb/typec/ucsi/cros_ec_ucsi.c b/drivers/usb/typec/ucsi/cros_ec_ucsi.c
new file mode 100644
index 000000000000..55b7ccc3f4e1
--- /dev/null
+++ b/drivers/usb/typec/ucsi/cros_ec_ucsi.c
@@ -0,0 +1,337 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * UCSI driver for ChromeOS EC
+ *
+ * Copyright 2024 Google LLC.
+ */
+
+#include <linux/container_of.h>
+#include <linux/dev_printk.h>
+#include <linux/jiffies.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_usbpd_notify.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+
+#include "ucsi.h"
+
+/*
+ * Maximum size in bytes of a UCSI message between AP and EC
+ */
+#define MAX_EC_DATA_SIZE	256
+
+/*
+ * Maximum time in milliseconds the cros_ec_ucsi driver
+ * will wait for a response to a command or and ack.
+ */
+#define WRITE_TMO_MS		5000
+
+/* Number of times to attempt recovery from a write timeout before giving up. */
+#define WRITE_TMO_CTR_MAX	5
+
+struct cros_ucsi_data {
+	struct device *dev;
+	struct ucsi *ucsi;
+
+	struct cros_ec_device *ec;
+	struct notifier_block nb;
+	struct work_struct work;
+	struct delayed_work write_tmo;
+	int tmo_counter;
+
+	struct completion complete;
+	unsigned long flags;
+};
+
+static int cros_ucsi_read(struct ucsi *ucsi, unsigned int offset, void *val,
+			  size_t val_len)
+{
+	struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
+	struct ec_params_ucsi_ppm_get req = {
+		.offset = offset,
+		.size = val_len,
+	};
+	int ret;
+
+	if (val_len > MAX_EC_DATA_SIZE) {
+		dev_err(udata->dev, "Can't read %zu bytes. Too big.", val_len);
+		return -EINVAL;
+	}
+
+	ret = cros_ec_cmd(udata->ec, 0, EC_CMD_UCSI_PPM_GET,
+			  &req, sizeof(req), val, val_len);
+	if (ret < 0) {
+		dev_warn(udata->dev, "Failed to send EC message UCSI_PPM_GET: error=%d", ret);
+		return ret;
+	}
+	return 0;
+}
+
+static int cros_ucsi_read_version(struct ucsi *ucsi, u16 *version)
+{
+	return cros_ucsi_read(ucsi, UCSI_VERSION, version, sizeof(*version));
+}
+
+static int cros_ucsi_read_cci(struct ucsi *ucsi, u32 *cci)
+{
+	return cros_ucsi_read(ucsi, UCSI_CCI, cci, sizeof(*cci));
+}
+
+static int cros_ucsi_read_message_in(struct ucsi *ucsi, void *val,
+				     size_t val_len)
+{
+	return cros_ucsi_read(ucsi, UCSI_MESSAGE_IN, val, val_len);
+}
+
+static int cros_ucsi_async_control(struct ucsi *ucsi, u64 cmd)
+{
+	struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
+	u8 ec_buf[sizeof(struct ec_params_ucsi_ppm_set) + sizeof(cmd)];
+	struct ec_params_ucsi_ppm_set *req = (struct ec_params_ucsi_ppm_set *) ec_buf;
+	int ret;
+
+	req->offset = UCSI_CONTROL;
+	memcpy(req->data, &cmd, sizeof(cmd));
+	ret = cros_ec_cmd(udata->ec, 0, EC_CMD_UCSI_PPM_SET,
+			  req, sizeof(ec_buf), NULL, 0);
+	if (ret < 0) {
+		dev_warn(udata->dev, "Failed to send EC message UCSI_PPM_SET: error=%d", ret);
+		return ret;
+	}
+	return 0;
+}
+
+static int cros_ucsi_sync_control(struct ucsi *ucsi, u64 cmd)
+{
+	struct cros_ucsi_data *udata = ucsi_get_drvdata(ucsi);
+	int ret;
+
+	ret = ucsi_sync_control_common(ucsi, cmd);
+	switch (ret) {
+	case -EBUSY:
+		/* EC may return -EBUSY if CCI.busy is set.
+		 * Convert this to a timeout.
+		 */
+	case -ETIMEDOUT:
+		/* Schedule recovery attempt when we timeout
+		 * or tried to send a command while still busy.
+		 */
+		cancel_delayed_work_sync(&udata->write_tmo);
+		schedule_delayed_work(&udata->write_tmo,
+				      msecs_to_jiffies(WRITE_TMO_MS));
+		break;
+	case 0:
+		/* Successful write. Cancel any pending recovery work. */
+		cancel_delayed_work_sync(&udata->write_tmo);
+		break;
+	}
+
+	return ret;
+}
+
+struct ucsi_operations cros_ucsi_ops = {
+	.read_version = cros_ucsi_read_version,
+	.read_cci = cros_ucsi_read_cci,
+	.read_message_in = cros_ucsi_read_message_in,
+	.async_control = cros_ucsi_async_control,
+	.sync_control = cros_ucsi_sync_control,
+};
+
+static void cros_ucsi_work(struct work_struct *work)
+{
+	struct cros_ucsi_data *udata = container_of(work, struct cros_ucsi_data, work);
+	u32 cci;
+
+	if (cros_ucsi_read_cci(udata->ucsi, &cci))
+		return;
+
+	ucsi_notify_common(udata->ucsi, cci);
+}
+
+static void cros_ucsi_write_timeout(struct work_struct *work)
+{
+	struct cros_ucsi_data *udata =
+		container_of(work, struct cros_ucsi_data, write_tmo.work);
+	u32 cci;
+	u64 cmd;
+
+	if (cros_ucsi_read(udata->ucsi, UCSI_CCI, &cci, sizeof(cci))) {
+		dev_err(udata->dev,
+			"Reading CCI failed; no write timeout recovery possible.");
+		return;
+	}
+
+	if (cci & UCSI_CCI_BUSY) {
+		udata->tmo_counter++;
+
+		if (udata->tmo_counter <= WRITE_TMO_CTR_MAX)
+			schedule_delayed_work(&udata->write_tmo,
+					      msecs_to_jiffies(WRITE_TMO_MS));
+		else
+			dev_err(udata->dev,
+				"PPM unresponsive - too many write timeouts.");
+
+		return;
+	}
+
+	/* No longer busy means we can reset our timeout counter. */
+	udata->tmo_counter = 0;
+
+	/* Need to ack previous command which may have timed out. */
+	if (cci & UCSI_CCI_COMMAND_COMPLETE) {
+		cmd = UCSI_ACK_CC_CI | UCSI_ACK_COMMAND_COMPLETE;
+		cros_ucsi_async_control(udata->ucsi, &cmd);
+
+		/* Check again after a few seconds that the system has
+		 * recovered to make sure our async write above was successful.
+		 */
+		schedule_delayed_work(&udata->write_tmo,
+				      msecs_to_jiffies(WRITE_TMO_MS));
+		return;
+	}
+
+	/* We recovered from a previous timeout. Treat this as a recovery from
+	 * suspend and call resume.
+	 */
+	ucsi_resume(udata->ucsi);
+}
+
+static int cros_ucsi_event(struct notifier_block *nb,
+			   unsigned long host_event, void *_notify)
+{
+	struct cros_ucsi_data *udata = container_of(nb, struct cros_ucsi_data, nb);
+
+	if (!(host_event & PD_EVENT_PPM))
+		return NOTIFY_OK;
+
+	dev_dbg(udata->dev, "UCSI notification received");
+	flush_work(&udata->work);
+	schedule_work(&udata->work);
+
+	return NOTIFY_OK;
+}
+
+static void cros_ucsi_destroy(struct cros_ucsi_data *udata)
+{
+	cros_usbpd_unregister_notify(&udata->nb);
+	cancel_delayed_work_sync(&udata->write_tmo);
+	cancel_work_sync(&udata->work);
+	ucsi_destroy(udata->ucsi);
+}
+
+static int cros_ucsi_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_dev *ec_data = dev_get_drvdata(dev->parent);
+	struct cros_ucsi_data *udata;
+	int ret;
+
+	udata = devm_kzalloc(dev, sizeof(*udata), GFP_KERNEL);
+	if (!udata)
+		return -ENOMEM;
+
+	udata->dev = dev;
+
+	udata->ec = ec_data->ec_dev;
+	if (!udata->ec) {
+		dev_err(dev, "couldn't find parent EC device");
+		return -ENODEV;
+	}
+
+	platform_set_drvdata(pdev, udata);
+
+	INIT_WORK(&udata->work, cros_ucsi_work);
+	INIT_DELAYED_WORK(&udata->write_tmo, cros_ucsi_write_timeout);
+	init_completion(&udata->complete);
+
+	udata->ucsi = ucsi_create(dev, &cros_ucsi_ops);
+	if (IS_ERR(udata->ucsi)) {
+		dev_err(dev, "failed to allocate UCSI instance");
+		return PTR_ERR(udata->ucsi);
+	}
+
+	ucsi_set_drvdata(udata->ucsi, udata);
+
+	udata->nb.notifier_call = cros_ucsi_event;
+	ret = cros_usbpd_register_notify(&udata->nb);
+	if (ret) {
+		dev_err(dev, "failed to register notifier: error=%d", ret);
+		ucsi_destroy(udata->ucsi);
+		return ret;
+	}
+
+	ret = ucsi_register(udata->ucsi);
+	if (ret) {
+		dev_err(dev, "failed to register UCSI: error=%d", ret);
+		cros_ucsi_destroy(udata);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void cros_ucsi_remove(struct platform_device *dev)
+{
+	struct cros_ucsi_data *udata = platform_get_drvdata(dev);
+
+	ucsi_unregister(udata->ucsi);
+	cros_ucsi_destroy(udata);
+}
+
+static int __maybe_unused cros_ucsi_suspend(struct device *dev)
+{
+	struct cros_ucsi_data *udata = dev_get_drvdata(dev);
+
+	cancel_delayed_work_sync(&udata->write_tmo);
+	cancel_work_sync(&udata->work);
+
+	return 0;
+}
+
+static void __maybe_unused cros_ucsi_complete(struct device *dev)
+{
+	struct cros_ucsi_data *udata = dev_get_drvdata(dev);
+
+	ucsi_resume(udata->ucsi);
+}
+
+/*
+ * UCSI protocol is also used on ChromeOS platforms which reply on
+ * cros_ec_lpc.c driver for communication with embedded controller (EC).
+ * On such platforms communication with the EC is not available until
+ * the .complete() callback of the cros_ec_lpc driver is executed.
+ * For this reason we delay ucsi_resume() until the .complete() stage
+ * otherwise UCSI SET_NOTIFICATION_ENABLE command will fail and we won't
+ * receive any UCSI notifications from the EC where PPM is implemented.
+ */
+static const struct dev_pm_ops cros_ucsi_pm_ops = {
+#ifdef CONFIG_PM_SLEEP
+	.suspend = cros_ucsi_suspend,
+	.complete = cros_ucsi_complete,
+#endif
+};
+
+static const struct platform_device_id cros_ucsi_id[] = {
+	{ KBUILD_MODNAME, 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, cros_ucsi_id);
+
+static struct platform_driver cros_ucsi_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.pm = &cros_ucsi_pm_ops,
+	},
+	.id_table = cros_ucsi_id,
+	.probe = cros_ucsi_probe,
+	.remove = cros_ucsi_remove,
+};
+
+module_platform_driver(cros_ucsi_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("UCSI driver for ChromeOS EC");
-- 
2.47.0.338.g60cca15819-goog