usb: typec: ucsi: Add debugfs for ucsi commands

Add support for UCSI commands through the following debugfs:
  # /sys/kernel/debug/usb/ucsi/$UCSI_DEVICE/command
  # /sys/kernel/debug/usb/ucsi/$UCSI_DEVICE/response

Eg: To execute UCSI GetCapabilities:
  # echo 0x6 > /sys/kernel/debug/usb/ucsi/<ucsi device>/command
Then read the result,
  # cat /sys/kernel/debug/usb/ucsi/<ucsi device>/response
    0x02000320000000020000ff0400000445

UCSI command will be written into the command file and the
response for the command can be viewed under the response file.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Saranya Gopal <saranya.gopal@intel.com>
Co-developed-by: Rajaram Regupathy <rajaram.regupathy@intel.com>
Signed-off-by: Rajaram Regupathy <rajaram.regupathy@intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20230807105205.742819-1-saranya.gopal@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/ucsi/Kconfig

@@ -4,6 +4,7 @@ config TYPEC_UCSI
 	tristate "USB Type-C Connector System Software Interface driver"
 	depends on !CPU_BIG_ENDIAN
 	depends on USB_ROLE_SWITCH || !USB_ROLE_SWITCH
+	select USB_COMMON if DEBUG_FS
 	help
 	  USB Type-C Connector System Software Interface (UCSI) is a
 	  specification for an interface that allows the operating system to

drivers/usb/typec/ucsi/Makefile

@@ -5,6 +5,8 @@ obj-$(CONFIG_TYPEC_UCSI)		+= typec_ucsi.o
 
 typec_ucsi-y				:= ucsi.o
 
+typec_ucsi-$(CONFIG_DEBUG_FS)		+= debugfs.o
+
 typec_ucsi-$(CONFIG_TRACING)		+= trace.o
 
 ifneq ($(CONFIG_POWER_SUPPLY),)

drivers/usb/typec/ucsi/debugfs.c

@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * UCSI debugfs interface
+ *
+ * Copyright (C) 2023 Intel Corporation
+ *
+ * Authors: Rajaram Regupathy <rajaram.regupathy@intel.com>
+ *	    Gopal Saranya <saranya.gopal@intel.com>
+ */
+#include <linux/debugfs.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/usb.h>
+
+#include <asm/errno.h>
+
+#include "ucsi.h"
+
+static struct dentry *ucsi_debugfs_root;
+
+static int ucsi_cmd(void *data, u64 val)
+{
+	struct ucsi *ucsi = data;
+	int ret;
+
+	memset(&ucsi->debugfs->response, 0, sizeof(ucsi->debugfs->response));
+	ucsi->debugfs->status = 0;
+
+	switch (UCSI_COMMAND(val)) {
+	case UCSI_SET_UOM:
+	case UCSI_SET_UOR:
+	case UCSI_SET_PDR:
+	case UCSI_CONNECTOR_RESET:
+		ret = ucsi_send_command(ucsi, val, NULL, 0);
+		break;
+	case UCSI_GET_CAPABILITY:
+	case UCSI_GET_CONNECTOR_CAPABILITY:
+	case UCSI_GET_ALTERNATE_MODES:
+	case UCSI_GET_CURRENT_CAM:
+	case UCSI_GET_PDOS:
+	case UCSI_GET_CABLE_PROPERTY:
+	case UCSI_GET_CONNECTOR_STATUS:
+		ret = ucsi_send_command(ucsi, val,
+					&ucsi->debugfs->response,
+					sizeof(ucsi->debugfs->response));
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	if (ret < 0) {
+		ucsi->debugfs->status = ret;
+		return ret;
+	}
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(ucsi_cmd_fops, NULL, ucsi_cmd, "0x%llx\n");
+
+static int ucsi_resp_show(struct seq_file *s, void *not_used)
+{
+	struct ucsi *ucsi = s->private;
+
+	if (ucsi->debugfs->status)
+		return ucsi->debugfs->status;
+
+	seq_printf(s, "0x%016llx%016llx\n", ucsi->debugfs->response.high,
+		   ucsi->debugfs->response.low);
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ucsi_resp);
+
+void ucsi_debugfs_register(struct ucsi *ucsi)
+{
+	ucsi->debugfs = kzalloc(sizeof(*ucsi->debugfs), GFP_KERNEL);
+	if (!ucsi->debugfs)
+		return;
+
+	ucsi->debugfs->dentry = debugfs_create_dir(dev_name(ucsi->dev), ucsi_debugfs_root);
+	debugfs_create_file("command", 0200, ucsi->debugfs->dentry, ucsi, &ucsi_cmd_fops);
+	debugfs_create_file("response", 0400, ucsi->debugfs->dentry, ucsi, &ucsi_resp_fops);
+}
+
+void ucsi_debugfs_unregister(struct ucsi *ucsi)
+{
+	debugfs_remove_recursive(ucsi->debugfs->dentry);
+	kfree(ucsi->debugfs);
+}
+
+void ucsi_debugfs_init(void)
+{
+	ucsi_debugfs_root = debugfs_create_dir("ucsi", usb_debug_root);
+}
+
+void ucsi_debugfs_exit(void)
+{
+	debugfs_remove(ucsi_debugfs_root);
+}

drivers/usb/typec/ucsi/ucsi.c

@@ -1530,6 +1530,7 @@ EXPORT_SYMBOL_GPL(ucsi_create);
  */
 void ucsi_destroy(struct ucsi *ucsi)
 {
+	ucsi_debugfs_unregister(ucsi);
 	kfree(ucsi);
 }
 EXPORT_SYMBOL_GPL(ucsi_destroy);
@@ -1552,6 +1553,7 @@ int ucsi_register(struct ucsi *ucsi)
 
 	queue_delayed_work(system_long_wq, &ucsi->work, 0);
 
+	ucsi_debugfs_register(ucsi);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ucsi_register);
@@ -1611,6 +1613,19 @@ void ucsi_unregister(struct ucsi *ucsi)
 }
 EXPORT_SYMBOL_GPL(ucsi_unregister);
 
+static int __init ucsi_module_init(void)
+{
+	ucsi_debugfs_init();
+	return 0;
+}
+module_init(ucsi_module_init);
+
+static void __exit ucsi_module_exit(void)
+{
+	ucsi_debugfs_exit();
+}
+module_exit(ucsi_module_exit);
+
 MODULE_AUTHOR("Heikki Krogerus <heikki.krogerus@linux.intel.com>");
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("USB Type-C Connector System Software Interface driver");

drivers/usb/typec/ucsi/ucsi.h

@@ -15,6 +15,7 @@
 
 struct ucsi;
 struct ucsi_altmode;
+struct dentry;
 
 /* UCSI offsets (Bytes) */
 #define UCSI_VERSION			0
@@ -277,6 +278,16 @@ struct ucsi_connector_status {
 
 /* -------------------------------------------------------------------------- */
 
+struct ucsi_debugfs_entry {
+	u64 command;
+	struct ucsi_data {
+		u64 low;
+		u64 high;
+	} response;
+	u32 status;
+	struct dentry *dentry;
+};
+
 struct ucsi {
 	u16 version;
 	struct device *dev;
@@ -286,6 +297,7 @@ struct ucsi {
 
 	struct ucsi_capability cap;
 	struct ucsi_connector *connector;
+	struct ucsi_debugfs_entry *debugfs;
 
 	struct work_struct resume_work;
 	struct delayed_work work;
@@ -388,6 +400,18 @@ static inline void
 ucsi_displayport_remove_partner(struct typec_altmode *adev) { }
 #endif /* CONFIG_TYPEC_DP_ALTMODE */
 
+#ifdef CONFIG_DEBUG_FS
+void ucsi_debugfs_init(void);
+void ucsi_debugfs_exit(void);
+void ucsi_debugfs_register(struct ucsi *ucsi);
+void ucsi_debugfs_unregister(struct ucsi *ucsi);
+#else
+static inline void ucsi_debugfs_init(void) { }
+static inline void ucsi_debugfs_exit(void) { }
+static inline void ucsi_debugfs_register(struct ucsi *ucsi) { }
+static inline void ucsi_debugfs_unregister(struct ucsi *ucsi) { }
+#endif /* CONFIG_DEBUG_FS */
+
 /*
  * NVIDIA VirtualLink (svid 0x955) has two altmode. VirtualLink
  * DP mode with vdo=0x1 and NVIDIA test mode with vdo=0x3