Re: [PATCH V2 12/13] i3c: mipi-i3c-hci-pci: Add LTR support for Intel controllers

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

On 14/11/2025 22:09, Frank Li wrote:
> On Fri, Nov 14, 2025 at 08:13:55PM +0200, Adrian Hunter wrote:
>> Add support for Latency Tolerance Reporting (LTR) for Intel controllers.
>>
>> Implement PM ->set_latency_tolerance() callback to set LTR register values.
>> Also expose LTR register values via debugfs.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>
>>
>> Changes in V2:
>>
>> 	Make use of FIELD_PREP()
>> 	Improve handling of values that exceed the maximum
>>
>>
>>  .../master/mipi-i3c-hci/mipi-i3c-hci-pci.c    | 125 ++++++++++++++++++
>>  1 file changed, 125 insertions(+)
>>
> ...
>> +static void intel_ltr_expose(struct device *dev)
>> +{
>> +	dev->power.set_latency_tolerance = intel_ltr_set;
>> +	dev_pm_qos_expose_latency_tolerance(dev);
>> +}
>> +
>> +static void intel_ltr_hide(struct device *dev)
>> +{
>> +	dev_pm_qos_hide_latency_tolerance(dev);
>> +	dev->power.set_latency_tolerance = NULL;
>> +}
>> +
>> +static struct dentry *intel_actualize_debugfs_root(bool add)
>> +{
>> +	static struct dentry *debugfs_root;
>> +	static DEFINE_MUTEX(lock);
>> +	static int ref_cnt;
>> +
>> +	guard(mutex)(&lock);
>> +
>> +	ref_cnt += add ? 1 : -1;
>> +
>> +	if (ref_cnt) {
>> +		if (IS_ERR_OR_NULL(debugfs_root))
>> +			debugfs_root = debugfs_create_dir("intel_i3c", NULL);
> 
> I think it'd better to create common "i3c" debugfs root. So your device
> use debugfs_create_dir(dev_name(&hci->pci->dev), ...) under this common
> root.

The debugfs files are being created for the PCI device to contain PCI
LTR information.  The i3c module has nothing to do with that.

Also, currently, there is no module dependency between this PCI driver
and i3c, but a dependency would be necessary to coordinate the creation
and deletion of an 'i3c' debugfs directory.

The extra complexity can't be justified.

> 
> ...
> 
>> +
>>  static const struct mipi_i3c_hci_pci_info intel_info = {
>>  	.init = intel_i3c_init,
>> +	.exit = intel_exit,
>>  };
>>
>>  static int mipi_i3c_hci_pci_probe(struct pci_dev *pci,
>> --
>> 2.51.0
>>
>>
>> --
>> linux-i3c mailing list
>> linux-i3c@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-i3c


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