Date:   Tue, 11 Oct 2022 10:47:04 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Vadim Fedorenko <vfedorenko@...ek.ru>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, Vadim Fedorenko <vadfed@...com>
Subject: Re: [RFC PATCH v3 1/6] dpll: Add DPLL framework base functions

Tue, Oct 11, 2022 at 10:32:22AM CEST, jiri@...nulli.us wrote:
>Mon, Oct 10, 2022 at 09:54:26PM CEST, vfedorenko@...ek.ru wrote:
>>On 10.10.2022 10:18, Jiri Pirko wrote:
>>> Mon, Oct 10, 2022 at 03:17:59AM CEST, vfedorenko@...ek.ru wrote:
>>> > From: Vadim Fedorenko <vadfed@...com>

[...]


>>I see your point. We do have hardware which allows changing type of SMA
>>connector, and even the direction, each SMA could be used as input/source or
>>output of different signals. But there are limitation, like not all SMAs can
>>produce IRIG-B signal or only some of them can be used to get GNSS 1PPS. The
>
>Okay, so that is not the *type* of source, but rather attribute of it.
>Example:
>
>$ dpll X show
>index 0
>  type EXT
>  signal 1PPS
>  supported_signals
>     1PPS 10MHz
>
>$ dpll X set source index 1 signal_type 10MHz
>$ dpll X show
>index 0
>  type EXT
>  signal 10MHz
>  supported_signals
>     1PPS 10MHz
>
>So one source with index 0 of type "EXT" (could be "SMA", does not
>matter) supports 1 signal types.
>
>
>Thinking about this more and to cover the case when one SMA could be
>potencially used for input and output. It already occured to me that
>source/output are quite similar, have similar/same attributes. What if
>they are merged together to say a "pin" object only with extra
>PERSONALITY attribute?
>
>Example:
>
>-> DPLL_CMD_PIN_GET - dump
>      ATTR_DEVICE_ID X
>
><- DPLL_CMD_PIN_GET
>
>       ATTR_DEVICE_ID X
>       ATTR_PIN_INDEX 0
>       ATTR_PIN_TYPE EXT
>       ATTR_PIN_SIGNAL 1PPS   (selected signal)
>       ATTR_PIN_SUPPORTED_SIGNALS (nest)
>         ATTR_PIN_SIGNAL 1PPS
>         ATTR_PIN_SIGNAL 10MHZ
>       ATTR_PIN_PERSONALITY OUTPUT   (selected personality)
>       ATTR_PIN_SUPPORTED_PERSONALITIES (nest)
>         ATTR_PIN_PERSONALITY DISCONNECTED
>         ATTR_PIN_PERSONALITY INPUT
>         ATTR_PIN_PERSONALITY OUTPUT     (note this supports both input and
>					  output)
>
>       ATTR_DEVICE_ID X
>       ATTR_PIN_INDEX 1
>       ATTR_PIN_TYPE EXT
>       ATTR_PIN_SIGNAL 10MHz   (selected signal)
>       ATTR_PIN_SUPPORTED_SIGNALS (nest)
>         ATTR_PIN_SIGNAL 1PPS
>         ATTR_PIN_SIGNAL 10MHZ
>       ATTR_PIN_PERSONALITY DISCONNECTED   (selected personality - not
>					    connected currently)
>       ATTR_PIN_SUPPORTED_PERSONALITIES (nest)
>         ATTR_PIN_PERSONALITY DISCONNECTED
>         ATTR_PIN_PERSONALITY INPUT      (note this supports only input)
>
>       ATTR_DEVICE_ID X
>       ATTR_PIN_INDEX 2
>       ATTR_PIN_TYPE GNSS
>       ATTR_PIN_SIGNAL 1PPS   (selected signal)
>       ATTR_PIN_SUPPORTED_SIGNALS (nest)
>         ATTR_PIN_SIGNAL 1PPS
>       ATTR_PIN_PERSONALITY INPUT   (selected personality - note this is
>				     now he selected source, being only
>				     pin with INPUT personality)
>       ATTR_PIN_SUPPORTED_PERSONALITIES (nest)
>         ATTR_PIN_PERSONALITY DISCONNECTED
>         ATTR_PIN_PERSONALITY INPUT      (note this supports only input)
>
>       ATTR_DEVICE_ID X
>       ATTR_PIN_INDEX 3
>       ATTR_PIN_TYPE SYNCE_ETH_PORT
>       ATTR_PIN_NETDEV_IFINDEX 20
>       ATTR_PIN_PERSONALITY OUTPUT   (selected personality)
>       ATTR_PIN_SUPPORTED_PERSONALITIES (nest)
>         ATTR_PIN_PERSONALITY DISCONNECTED
>         ATTR_PIN_PERSONALITY INPUT
>         ATTR_PIN_PERSONALITY OUTPUT     (note this supports both input and
>					  output)
>
>       ATTR_DEVICE_ID X
>       ATTR_PIN_INDEX 4
>       ATTR_PIN_TYPE SYNCE_ETH_PORT
>       ATTR_PIN_NETDEV_IFINDEX 30
>       ATTR_PIN_PERSONALITY OUTPUT   (selected personality)
>       ATTR_PIN_SUPPORTED_PERSONALITIES (nest)
>         ATTR_PIN_PERSONALITY DISCONNECTED
>         ATTR_PIN_PERSONALITY INPUT
>         ATTR_PIN_PERSONALITY OUTPUT     (note this supports both input and
>					  output)
>
>
>This allows the user to actually see the full picture:
>1) all input/output pins in a single list, no duplicates
>2) each pin if of certain type (ATTR_PIN_TYPE) EXT/GNSS/SYNCE_ETH_PORT
>3) the pins that can change signal type contain the selected and list of
>   supported signal types (ATTR_PIN_SIGNAL, ATTR_PIN_SUPPORTED_SIGNALS)
>4) direction/connection of the pin to the DPLL is exposed over
>   ATTR_PIN_PERSONALITY. For each pin, the driver would expose it can
>   act as INPUT/OUTPUT and even more, it can indicate the pin can
>   disconnect from DPLL entirely (if possible).
>5) user can select the source by setting ATTR_PIN_PERSONALITY of certain
>   pin to INPUT. Only one pin could be set to INPUT and that is the
>   souce of DPLL.
>   In case no pin have personality set to INPUT, the DPLL is
>   free-running.

Okay, thinking about it some more, I would leave the source select
indepentent from the ATTR_PIN_PERSONALITY and selectable using device
set cmd and separate attribute. It works better even more when consider
autoselect mode.

Well of course only pins with ATTR_PIN_PERSONALITY INPUT could be
selected as source.


>
>This would introduce quite nice flexibility, exposes source/output
>capabilities and provides good visilibity of current configuration.
>
>
>>interface was created to cover such case. I believe we have to improve it to
>>cover SyncE configuration better, but I personally don't have SyncE hardware
>>ready to test and that's why I have to rely on suggestions from yours or
>>Arkadiusz's experience. From what I can see now there is need for special
>>attribute to link source to net device, and I'm happy to add it. In case of
>>fixed configuration of sources, the device should provide only one type as
>>supported and that's it.
>>

[...]

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