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

[Adrian Hunter]

On 17/11/2025 17:59, Frank Li wrote:
> On Mon, Nov 17, 2025 at 01:36:36PM +0200, Adrian Hunter wrote:
>> 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 at 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.
> 
> Don't post new versin before we close open discussion. I see your post
> patch before this message.

Sorry, but it is late in the release cycle, and it saves time when we
are in different time zones.

> 
> So, I think not necessary to create to root, which cause complex, (need
> lock, and refer counter).

So you are OK with V3?

> 
> Frank
> 
>>
>>>
>>> ...
>>>
>>>> +
>>>>  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
>>>>
>>>>
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>>
>>
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