Re: [RFC PATCH net-next] dt-bindings: dpll: Add per-channel Ethernet reference property

[Ivan Vecera <ivecera@redhat.com>]

On 09. 09. 25 3:50 odp., Andrew Lunn wrote:
>>>> Yesterday I was considering the implementation from the DPLL driver's
>>>> perspective and encountered a problem when the relation is defined from
>>>> the Ethernet controller's perspective. In that case, it would be
>>>> necessary to enumerate all devices that contain a “dpll” property whose
>>>> value references this DPLL device.
>>>
>>> Why is that?
>>
>> Because the DPLL driver has to find a mac-address of the ethernet
>> controller to generate clock identity that is used for DPLL device
>> registration.
> 
> Maybe this API is the wrong way around? Maybe what you want is that
> the MAC driver says to the DPLL driver: hey, you are my clock
> provider, here is an ID to use, please start providing me a clock?

Yes, this could be fine but there is a problem because clock id is part
of DPLL device and pins registration and it is not possible to change
the clock id without full de-re-registration. I have provided in zl3073x
a user to change the clock id via devlink but it means that the driver
has to unregister all dpll devices and pins and register them under
different clock id.

> So it is the MAC driver which will follow the phandle, and then make a
> call to bind the dpll to the MAC, and then provide it with the ID?

In fact that would be enough to expose from the DPLL core a function
to change clock id of the existing DPLL devices.

E.g.

int dpll_clock_id_change(struct module *module, u64 clock_id,
			 u64 new_clock_id)
{
	struct dpll_device *dpll_pos;
	struct dpll_pin *pin_pos;
	unsigned long i;

	mutex_lock(&dpll_lock);
	/* Change clock_id of all devices registered by given module
	 * with given clock_id.
	 */
	xa_for_each(&dpll_device_xa, i, dpll_pos) {
		if (dpll->clock_id == clock_id &&
		    dpll->module == module)
			dpll_pos->clock_id = new_clock_id;
		}
	}
	/* Change clock_id of all pins registered by given module
	 * with given clock_id.
	 */
	xa_for_each(&dpll_pin_xa, i, pos) {
		if (pin_pos->clock_id == clock_id &&
		    pin_pos->module == module) {
			pos->clock_id = new_clock_id;
		}
	}
	mutex_unlock(&dpll_lock);
}

With this, the standalone DPLL driver can register devices and pins with
arbitrary clock_id and then the MAC driver can change it.

Thoughts?

Thanks,
Ivan