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

Document sysfs attribute dev_nack_retry_cnt that controls the number of
automatic retries performed by the I3C controller when a target device
returns a NACK

Add a `dev_nack_retry_count` sysfs attribute to allow reading and updating
the device NACK retry count. A new `dev_nack_retry_count` 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@altera.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
---
 Documentation/ABI/testing/sysfs-bus-i3c | 11 +++++++
 drivers/i3c/master.c                    | 39 +++++++++++++++++++++++++
 include/linux/i3c/master.h              |  6 ++++
 3 files changed, 56 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-i3c b/Documentation/ABI/testing/sysfs-bus-i3c
index c812ab180ff4..c1e048957a01 100644
--- a/Documentation/ABI/testing/sysfs-bus-i3c
+++ b/Documentation/ABI/testing/sysfs-bus-i3c
@@ -161,3 +161,14 @@ Contact:	linux-i3c@vger.kernel.org
 Description:
 		These directories are just symbolic links to
 		/sys/bus/i3c/devices/i3c-<bus-id>/<bus-id>-<device-pid>.
+
+What:		/sys/bus/i3c/devices/i3c-<bus-id>/<bus-id>-<device-pid>/dev_nack_retry_count
+KernelVersion:  6.18
+Contact:	linux-i3c@vger.kernel.org
+Description:
+		Expose the dev_nak_retry_count which controls the number of
+		automatic retries that will be performed by the controller when
+		the target device returns a NACK response. A value of 0 disables
+		the automatic retries. Exist only when I3C constroller supports
+		this retry on nack feature.
+
diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index d946db75df70..87f0c7b5df80 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -685,6 +685,39 @@ static ssize_t hotjoin_show(struct device *dev, struct device_attribute *da, cha
 
 static DEVICE_ATTR_RW(hotjoin);
 
+static ssize_t dev_nack_retry_count_show(struct device *dev,
+					 struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%u\n", dev_to_i3cmaster(dev)->dev_nack_retry_count);
+}
+
+static ssize_t dev_nack_retry_count_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 = dev_to_i3cmaster(dev);
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	i3c_bus_maintenance_lock(i3cbus);
+	ret = master->ops->set_dev_nack_retry(master, val);
+	i3c_bus_maintenance_unlock(i3cbus);
+
+	if (ret)
+		return ret;
+
+	master->dev_nack_retry_count = val;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(dev_nack_retry_count);
+
 static struct attribute *i3c_masterdev_attrs[] = {
 	&dev_attr_mode.attr,
 	&dev_attr_current_master.attr,
@@ -2962,6 +2995,9 @@ 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_count);
+
 	return 0;
 
 err_del_dev:
@@ -2987,6 +3023,9 @@ 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_count);
+
 	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..b0fe3c266746 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 +493,8 @@ 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,
+				  unsigned long dev_nack_retry_cnt);
 };
 
 /**
@@ -514,6 +518,7 @@ struct i3c_master_controller_ops {
  *	in a thread context. Typical examples are Hot Join processing which
  *	requires taking the bus lock in maintenance, which in turn, can only
  *	be done from a sleep-able context
+ * @dev_nack_retry_count: retry count when slave device nack
  *
  * A &struct i3c_master_controller has to be registered to the I3C subsystem
  * through i3c_master_register(). None of &struct i3c_master_controller fields
@@ -534,6 +539,7 @@ struct i3c_master_controller {
 	} boardinfo;
 	struct i3c_bus bus;
 	struct workqueue_struct *wq;
+	unsigned int dev_nack_retry_count;
 };
 
 /**
-- 
2.49.GIT