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Subject[PATCH 1/9] usb: typec: Add support for retimers
Date
Introduce a retimer device class and associated functions that register
and use retimer "switch" devices. These operate in a manner similar to
the "mode-switch" and help configure retimers that exist between the
Type-C connector and host controller(s).

Type C ports can be linked to retimers using firmware node device
references (again, in a manner similar to "mode-switch").

Signed-off-by: Prashant Malani <pmalani@chromium.org>
---
drivers/usb/typec/Makefile | 2 +-
drivers/usb/typec/class.c | 9 +-
drivers/usb/typec/class.h | 1 +
drivers/usb/typec/retimer.c | 168 ++++++++++++++++++++++++++++++
drivers/usb/typec/retimer.h | 15 +++
include/linux/usb/typec_retimer.h | 45 ++++++++
6 files changed, 238 insertions(+), 2 deletions(-)
create mode 100644 drivers/usb/typec/retimer.c
create mode 100644 drivers/usb/typec/retimer.h
create mode 100644 include/linux/usb/typec_retimer.h

diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
index 2f174cd3e5df..4955d9af0811 100644
--- a/drivers/usb/typec/Makefile
+++ b/drivers/usb/typec/Makefile
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_TYPEC) += typec.o
-typec-y := class.o mux.o bus.o pd.o
+typec-y := class.o mux.o bus.o pd.o retimer.o
typec-$(CONFIG_ACPI) += port-mapper.o
obj-$(CONFIG_TYPEC) += altmodes/
obj-$(CONFIG_TYPEC_TCPM) += tcpm/
diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index bbc46b14f99a..2fa0b3718d23 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -2299,10 +2299,14 @@ static int __init typec_init(void)
if (ret)
goto err_unregister_bus;

- ret = class_register(&typec_class);
+ ret = class_register(&typec_retimer_class);
if (ret)
goto err_unregister_mux_class;

+ ret = class_register(&typec_class);
+ if (ret)
+ goto err_unregister_retimer_class;
+
ret = usb_power_delivery_init();
if (ret)
goto err_unregister_class;
@@ -2312,6 +2316,9 @@ static int __init typec_init(void)
err_unregister_class:
class_unregister(&typec_class);

+err_unregister_retimer_class:
+ class_unregister(&typec_retimer_class);
+
err_unregister_mux_class:
class_unregister(&typec_mux_class);

diff --git a/drivers/usb/typec/class.h b/drivers/usb/typec/class.h
index b531f9853bc0..1bb1da124109 100644
--- a/drivers/usb/typec/class.h
+++ b/drivers/usb/typec/class.h
@@ -76,6 +76,7 @@ extern const struct device_type typec_port_dev_type;
#define is_typec_port(dev) ((dev)->type == &typec_port_dev_type)

extern struct class typec_mux_class;
+extern struct class typec_retimer_class;
extern struct class typec_class;

#if defined(CONFIG_ACPI)
diff --git a/drivers/usb/typec/retimer.c b/drivers/usb/typec/retimer.c
new file mode 100644
index 000000000000..2fa0aeb9363c
--- /dev/null
+++ b/drivers/usb/typec/retimer.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2022 Google LLC
+ *
+ * USB Type-C Retimer support.
+ * Author: Prashant Malani <pmalani@chromium.org>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+#include "class.h"
+#include "retimer.h"
+
+static bool dev_name_ends_with(struct device *dev, const char *suffix)
+{
+ const char *name = dev_name(dev);
+ const int name_len = strlen(name);
+ const int suffix_len = strlen(suffix);
+
+ if (suffix_len > name_len)
+ return false;
+
+ return strcmp(name + (name_len - suffix_len), suffix) == 0;
+}
+
+static int retimer_fwnode_match(struct device *dev, const void *fwnode)
+{
+ return dev_fwnode(dev) == fwnode && dev_name_ends_with(dev, "-retimer");
+}
+
+static void *typec_retimer_match(struct fwnode_handle *fwnode, const char *id, void *data)
+{
+ struct device *dev = class_find_device(&typec_retimer_class, NULL, fwnode,
+ retimer_fwnode_match);
+
+ return dev ? to_typec_retimer(dev) : ERR_PTR(-EPROBE_DEFER);
+}
+
+/**
+ * fwnode_typec_retimer_get - Find USB Type-C retimer.
+ * @fwnode: The caller device node.
+ *
+ * Finds a retimer linked to the caller. This function is primarily meant for the
+ * Type-C drivers. Returns a reference to the retimer on success, NULL if no
+ * matching connection was found, or ERR_PTR(-EPROBE_DEFER) when a connection
+ * was found but the retimer has not been enumerated yet.
+ */
+struct typec_retimer *fwnode_typec_retimer_get(struct fwnode_handle *fwnode)
+{
+ struct typec_retimer *retimer;
+
+ retimer = fwnode_connection_find_match(fwnode, "retimer-switch", NULL, typec_retimer_match);
+ if (!IS_ERR_OR_NULL(retimer))
+ WARN_ON(!try_module_get(retimer->dev.parent->driver->owner));
+
+ return retimer;
+}
+EXPORT_SYMBOL_GPL(fwnode_typec_retimer_get);
+
+/**
+ * typec_retimer_put - Release handle to a retimer.
+ * @retimer: USB Type-C Connector Retimer.
+ *
+ * Decrements reference count for @retimer.
+ */
+void typec_retimer_put(struct typec_retimer *retimer)
+{
+ if (!IS_ERR_OR_NULL(retimer)) {
+ module_put(retimer->dev.parent->driver->owner);
+ put_device(&retimer->dev);
+ }
+}
+EXPORT_SYMBOL_GPL(typec_retimer_put);
+
+int typec_retimer_set(struct typec_retimer *retimer, struct typec_retimer_state *state)
+{
+ if (IS_ERR_OR_NULL(retimer))
+ return 0;
+
+ return retimer->set(retimer, state);
+}
+EXPORT_SYMBOL_GPL(typec_retimer_set);
+
+static void typec_retimer_release(struct device *dev)
+{
+ kfree(to_typec_retimer(dev));
+}
+
+static const struct device_type typec_retimer_dev_type = {
+ .name = "retimer_switch",
+ .release = typec_retimer_release,
+};
+
+/**
+ * typec_retimer_register - Register a retimer device.
+ * @parent: Parent device.
+ * @desc: Retimer description.
+ *
+ * Some USB Type-C connectors have their physical lines routed through retimers before they
+ * reach muxes or host controllers. In some cases (for example: using alternate modes)
+ * these retimers need to be reconfigured appropriately. This function registers retimer
+ * switches which route and potentially modify the signals on the Type C physical lines
+ * enroute to the host controllers.
+ */
+struct typec_retimer *
+typec_retimer_register(struct device *parent, const struct typec_retimer_desc *desc)
+{
+ struct typec_retimer *retimer;
+ int ret;
+
+ if (!desc || !desc->set)
+ return ERR_PTR(-EINVAL);
+
+ retimer = kzalloc(sizeof(*retimer), GFP_KERNEL);
+ if (!retimer)
+ return ERR_PTR(-ENOMEM);
+
+ retimer->set = desc->set;
+
+ device_initialize(&retimer->dev);
+ retimer->dev.parent = parent;
+ retimer->dev.fwnode = desc->fwnode;
+ retimer->dev.class = &typec_retimer_class;
+ retimer->dev.type = &typec_retimer_dev_type;
+ retimer->dev.driver_data = desc->drvdata;
+ dev_set_name(&retimer->dev, "%s-retimer",
+ desc->name ? desc->name : dev_name(parent));
+
+ ret = device_add(&retimer->dev);
+ if (ret) {
+ dev_err(parent, "failed to register retimer (%d)\n", ret);
+ put_device(&retimer->dev);
+ return ERR_PTR(ret);
+ }
+
+ return retimer;
+}
+EXPORT_SYMBOL_GPL(typec_retimer_register);
+
+/**
+ * typec_retimer_unregister - Unregister retimer device.
+ * @retimer: USB Type-C Connector retimer.
+ *
+ * Unregister retimer that was registered with typec_retimer_register().
+ */
+void typec_retimer_unregister(struct typec_retimer *retimer)
+{
+ if (!IS_ERR_OR_NULL(retimer))
+ device_unregister(&retimer->dev);
+}
+EXPORT_SYMBOL_GPL(typec_retimer_unregister);
+
+void *typec_retimer_get_drvdata(struct typec_retimer *retimer)
+{
+ return dev_get_drvdata(&retimer->dev);
+}
+EXPORT_SYMBOL_GPL(typec_retimer_get_drvdata);
+
+struct class typec_retimer_class = {
+ .name = "typec_retimer",
+ .owner = THIS_MODULE,
+};
diff --git a/drivers/usb/typec/retimer.h b/drivers/usb/typec/retimer.h
new file mode 100644
index 000000000000..fa15951d4846
--- /dev/null
+++ b/drivers/usb/typec/retimer.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __USB_TYPEC_RETIMER__
+#define __USB_TYPEC_RETIMER__
+
+#include <linux/usb/typec_retimer.h>
+
+struct typec_retimer {
+ struct device dev;
+ typec_retimer_set_fn_t set;
+};
+
+#define to_typec_retimer(_dev_) container_of(_dev_, struct typec_retimer, dev)
+
+#endif /* __USB_TYPEC_RETIMER__ */
diff --git a/include/linux/usb/typec_retimer.h b/include/linux/usb/typec_retimer.h
new file mode 100644
index 000000000000..5e036b3360e2
--- /dev/null
+++ b/include/linux/usb/typec_retimer.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __USB_TYPEC_RETIMER
+#define __USB_TYPEC_RETIMER
+
+#include <linux/property.h>
+#include <linux/usb/typec.h>
+
+struct device;
+struct typec_retimer;
+struct typec_altmode;
+struct fwnode_handle;
+
+struct typec_retimer_state {
+ struct typec_altmode *alt;
+ unsigned long mode;
+ void *data;
+};
+
+typedef int (*typec_retimer_set_fn_t)(struct typec_retimer *retimer,
+ struct typec_retimer_state *state);
+
+struct typec_retimer_desc {
+ struct fwnode_handle *fwnode;
+ typec_retimer_set_fn_t set;
+ const char *name;
+ void *drvdata;
+};
+
+struct typec_retimer *fwnode_typec_retimer_get(struct fwnode_handle *fwnode);
+void typec_retimer_put(struct typec_retimer *retimer);
+int typec_retimer_set(struct typec_retimer *retimer, struct typec_retimer_state *state);
+
+static inline struct typec_retimer *typec_retimer_get(struct device *dev)
+{
+ return fwnode_typec_retimer_get(dev_fwnode(dev));
+}
+
+struct typec_retimer *
+typec_retimer_register(struct device *parent, const struct typec_retimer_desc *desc);
+void typec_retimer_unregister(struct typec_retimer *retimer);
+
+void *typec_retimer_get_drvdata(struct typec_retimer *retimer);
+
+#endif /* __USB_TYPEC_RETIMER */
--
2.37.0.rc0.161.g10f37bed90-goog
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