linux-kernel - [PATCH v6 2/5] i3c: add sysfs attribute for device NACK retry

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Message-ID: <a12dcd1eee62e7394c233ce67e0463d4c3767fce.1764746266.git.adrianhoyin.ng@altera.com>
Date: Wed,  3 Dec 2025 15:21:03 +0800
From: adrianhoyin.ng@...era.com
To: alexandre.belloni@...tlin.com,
	Frank.Li@....com,
	linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: adrianhoyin.ng@...era.com
Subject: [PATCH v6 2/5] i3c: add sysfs attribute for device NACK retry

From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>

Add a `dev_nack_retry` sysfs attribute to allow reading and updating the
device NACK retry count. A new `dev_nack_retry` field and an optional
`set_dev_nack_retry()` callback are added to i3c_master_controller.
The attribute is created only when the callback is implemented.

Updates are applied under the I3C bus maintenance lock to ensure safe
hardware reconfiguration.

Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
---
 drivers/i3c/master.c       | 41 ++++++++++++++++++++++++++++++++++++++
 include/linux/i3c/master.h |  5 +++++
 2 files changed, 46 insertions(+)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index d946db75df70..e67f54c6e865 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -685,6 +685,41 @@ static ssize_t hotjoin_show(struct device *dev, struct device_attribute *da, cha
 
 static DEVICE_ATTR_RW(hotjoin);
 
+static ssize_t dev_nack_retry_show(struct device *dev, struct device_attribute *attr,
+				   char *buf)
+{
+	struct i3c_bus *i3cbus = dev_to_i3cbus(dev);
+
+	return sysfs_emit(buf, "%u\n", i3cbus->cur_master->common.master->dev_nack_retry);
+}
+
+static ssize_t dev_nack_retry_store(struct device *dev, struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	struct i3c_bus *i3cbus = dev_to_i3cbus(dev);
+	struct i3c_master_controller *master;
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	master = dev_to_i3cmaster(dev);
+	master->dev_nack_retry = val;
+
+	i3c_bus_maintenance_lock(i3cbus);
+	ret = master->ops->set_dev_nack_retry(master);
+	i3c_bus_maintenance_unlock(i3cbus);
+
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(dev_nack_retry);
+
 static struct attribute *i3c_masterdev_attrs[] = {
 	&dev_attr_mode.attr,
 	&dev_attr_current_master.attr,
@@ -2962,6 +2997,9 @@ int i3c_master_register(struct i3c_master_controller *master,
 	i3c_master_register_new_i3c_devs(master);
 	i3c_bus_normaluse_unlock(&master->bus);
 
+	if (master->ops->set_dev_nack_retry)
+		device_create_file(&master->dev, &dev_attr_dev_nack_retry);
+
 	return 0;
 
 err_del_dev:
@@ -2987,6 +3025,9 @@ void i3c_master_unregister(struct i3c_master_controller *master)
 {
 	i3c_bus_notify(&master->bus, I3C_NOTIFY_BUS_REMOVE);
 
+	if (master->ops->set_dev_nack_retry)
+		device_remove_file(&master->dev, &dev_attr_dev_nack_retry);
+
 	i3c_master_i2c_adapter_cleanup(master);
 	i3c_master_unregister_i3c_devs(master);
 	i3c_master_bus_cleanup(master);
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index c52a82dd79a6..ee254864c8d2 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -462,6 +462,8 @@ struct i3c_bus {
  * @enable_hotjoin: enable hot join event detect.
  * @disable_hotjoin: disable hot join event detect.
  * @set_speed: adjust I3C open drain mode timing.
+ * @set_dev_nack_retry: configure device NACK retry count for the master
+ *                      controller.
  */
 struct i3c_master_controller_ops {
 	int (*bus_init)(struct i3c_master_controller *master);
@@ -491,6 +493,7 @@ struct i3c_master_controller_ops {
 	int (*enable_hotjoin)(struct i3c_master_controller *master);
 	int (*disable_hotjoin)(struct i3c_master_controller *master);
 	int (*set_speed)(struct i3c_master_controller *master, enum i3c_open_drain_speed speed);
+	int (*set_dev_nack_retry)(struct i3c_master_controller *master);
 };
 
 /**
@@ -510,6 +513,7 @@ struct i3c_master_controller_ops {
  * @boardinfo: board-level information attached to devices connected on the bus
  * @bus: I3C bus exposed by this master
  * @wq: workqueue which can be used by master
+ * @dev_nack_retry: retry count when slave device nack
  *	drivers if they need to postpone operations that need to take place
  *	in a thread context. Typical examples are Hot Join processing which
  *	requires taking the bus lock in maintenance, which in turn, can only
@@ -534,6 +538,7 @@ struct i3c_master_controller {
 	} boardinfo;
 	struct i3c_bus bus;
 	struct workqueue_struct *wq;
+	unsigned int dev_nack_retry;
 };
 
 /**
-- 
2.49.GIT