linux-kernel - RE: [RFC PATCH v8 08/10] ice: implement dpll interface to control cgu

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Message-ID: <DM6PR11MB4657161D2871747A7B404EDD9B5FA@DM6PR11MB4657.namprd11.prod.outlook.com>
Date:   Mon, 19 Jun 2023 20:34:12 +0000
From:   "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
To:     Jiri Pirko <jiri@...nulli.us>
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Subject: RE: [RFC PATCH v8 08/10] ice: implement dpll interface to control cgu

>From: Jiri Pirko <jiri@...nulli.us>
>Sent: Saturday, June 10, 2023 6:37 PM
>
>Fri, Jun 09, 2023 at 02:18:51PM CEST, arkadiusz.kubalewski@...el.com wrote:
>
>[...]
>
>
>>+static int ice_dpll_mode_get(const struct dpll_device *dpll, void *priv,
>>+			     enum dpll_mode *mode,
>>+			     struct netlink_ext_ack *extack)
>>+{
>>+	*mode = DPLL_MODE_AUTOMATIC;
>
>I don't understand how the automatic mode could work with SyncE. The
>There is one pin exposed for one netdev. The SyncE daemon should select
>exacly one pin. How do you achieve that?
>Is is by setting DPLL_PIN_STATE_SELECTABLE on the pin-netdev you want to
>select and DPLL_PIN_STATE_DISCONNECTED on the rest?
>
>
>[...]

AUTOMATIC mode autoselects highest priority valid signal.
As you have pointed out, for SyncE selection, the user must be able to manually
select a pin state to enable recovery of signal from particular port.

In "ice" case there are 2 pins for network PHY clock signal recovery, and both
are parent pins (MUX-type). There are also 4 pins assigned to netdevs (one per
port). Thus passing a signal from PHY to the pin is done through the MUX-pin,
by selecting proper state on pin-parent pair (where parent pins is highest prio
pin on dpll).

Thank you!
Arkadiusz