Re: [PATCH V2 4/8] i3c: master: Add helper to query bus wakeup requirements

[Adrian Hunter <adrian.hunter@intel.com>]

On 28/07/2026 23:03, Frank Li wrote:
> On Tue, Jul 28, 2026 at 06:53:04PM +0300, Adrian Hunter wrote:
>> Add i3c_master_any_wakeup_enabled(), which iterates over the devices on
>> an I3C bus and reports whether any of them are enabled for system
>> wakeup and have IBI enabled.
>>
>> Controller drivers can use this helper to determine whether wakeup
>> support must remain available while the system is suspended.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>
>>
>> Changes in V2:
>>
>> 	i3c_master_any_wakeup_enabled() now also requires the device to
>> 	have IBI enabled, not just system wakeup enabled, so that a
>> 	device with no active IBI request does not keep PCI PME enabled.
>> 	desc->ibi_lock is taken while checking.  The commit message and
>> 	kernel-doc are updated to match.
>>
>>
>>  drivers/i3c/master.c       | 30 ++++++++++++++++++++++++++++++
>>  include/linux/i3c/master.h |  1 +
>>  2 files changed, 31 insertions(+)
>>
>> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
>> index 9d56ca08569a..dd49652425b4 100644
>> --- a/drivers/i3c/master.c
>> +++ b/drivers/i3c/master.c
>> @@ -2048,6 +2048,36 @@ static void i3c_master_reg_work_fn(struct work_struct *work)
>>  	i3c_master_register_new_i3c_devs(master);
>>  }
>>
>> +/**
>> + * i3c_master_any_wakeup_enabled() - check if any device can wake the system
>> + * @master: I3C master controller
>> + *
>> + * Iterate over devices on the bus and return true if any device has
>> + * system wakeup enabled and IBI enabled.
>> + *
>> + * Return: true if any device may wake the system via IBI, false otherwise.
>> + */
>> +bool i3c_master_any_wakeup_enabled(struct i3c_master_controller *master)
>> +{
> 
> This check most like introdouce rise condition.
> 
> if (i3c_master_any_wakeup_enabled())
> 	do_some_thing()
> 
> no lock protection, so between check i3c_master_any_wakeup_enabled() and
> do_some_thing(), condtion may be changed.

It should be called when the condition cannot change anymore.

It is being called on controller suspend path.  device_may_wakeup()
should not change after user space is frozen.  I3C device drivers have
already had their ->suspend() callbacks called, but should not really
be doing anything that alters the outcome of i3c_master_any_wakeup_enabled()
anyway.

> 
> Frank
> 
>> +	struct i3c_dev_desc *desc;
>> +	bool wakeup = false;
>> +
>> +	i3c_bus_normaluse_lock(&master->bus);
>> +	i3c_bus_for_each_i3cdev(&master->bus, desc) {
>> +		if (!desc->dev || !device_may_wakeup(&desc->dev->dev))
>> +			continue;
>> +		guard(mutex)(&desc->ibi_lock);
>> +		if (desc->ibi && desc->ibi->enabled) {
>> +			wakeup = true;
>> +			break;
>> +		}
>> +	}
>> +	i3c_bus_normaluse_unlock(&master->bus);
>> +
>> +	return wakeup;
>> +}
>> +EXPORT_SYMBOL_GPL(i3c_master_any_wakeup_enabled);
>> +
>>  /**
>>   * i3c_master_dma_map_single() - Map buffer for single DMA transfer
>>   * @dev: device object of a device doing DMA
>> diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
>> index 99f89fef7653..d8cdc7ff2459 100644
>> --- a/include/linux/i3c/master.h
>> +++ b/include/linux/i3c/master.h
>> @@ -748,6 +748,7 @@ void i3c_generic_ibi_recycle_slot(struct i3c_generic_ibi_pool *pool,
>>  				  struct i3c_ibi_slot *slot);
>>
>>  void i3c_master_queue_ibi(struct i3c_dev_desc *dev, struct i3c_ibi_slot *slot);
>> +bool i3c_master_any_wakeup_enabled(struct i3c_master_controller *master);
>>
>>  struct i3c_ibi_slot *i3c_master_get_free_ibi_slot(struct i3c_dev_desc *dev);
>>
>> --
>> 2.53.0
>>