From b58f47eb392680d4c6626c8b3b1fcf6412a0a02c Mon Sep 17 00:00:00 2001 From: Adrian Ng Ho Yin Date: Fri, 12 Dec 2025 17:02:55 +0800 Subject: [PATCH] i3c: add sysfs entry and attribute for Device NACK Retry count 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 Reviewed-by: Frank Li Link: https://patch.msgid.link/3c4b5082bde64024fc383c44bebeef89ad3c7ed3.1765529948.git.adrianhoyin.ng@altera.com Signed-off-by: Alexandre Belloni --- 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 c812ab180ff40..c1e048957a010 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-/-. + +What: /sys/bus/i3c/devices/i3c-/-/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 7f606c8716480..5e37ccc758e47 100644 --- a/drivers/i3c/master.c +++ b/drivers/i3c/master.c @@ -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); diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h index 58d01ed4cce75..d231c4fbc58b8 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; }; /** -- 2.47.3