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i3c: add sysfs entry and attribute for Device NACK Retry count

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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>
Link: https://patch.msgid.link/3c4b5082bde64024fc383c44bebeef89ad3c7ed3.1765529948.git.adrianhoyin.ng@altera.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Adrian Ng Ho Yin 2025-12-12 17:02:55 +08:00 committed by Alexandre Belloni
parent 8f0b4cce44
commit b58f47eb39
3 changed files with 56 additions and 0 deletions
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11
Documentation/ABI/testing/sysfs-bus-i3c
View File

@ -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.

39
drivers/i3c/master.c
View File

@ -683,6 +683,39 @@ 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,
@ -2959,6 +2992,9 @@ 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:
@ -2984,6 +3020,9 @@ 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);

6
include/linux/i3c/master.h
View File

@ -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;
};
/**