netdev - Re: [RFC PATCH v4 0/4] Create common DPLL/clock configuration API

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Message-ID: <Y8AeRnhwqT7Wo8OT@nanopsycho>
Date:   Thu, 12 Jan 2023 15:50:46 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
Cc:     Vadim Fedorenko <vfedorenko@...ek.ru>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [RFC PATCH v4 0/4] Create common DPLL/clock configuration API

Thu, Jan 12, 2023 at 01:23:29PM CET, arkadiusz.kubalewski@...el.com wrote:
>>From: Vadim Fedorenko <vfedorenko@...ek.ru>
>>Sent: Tuesday, November 29, 2022 10:37 PM
>>
>>Implement common API for clock/DPLL configuration and status reporting.
>>The API utilises netlink interface as transport for commands and event
>>notifications. This API aim to extend current pin configuration and make it
>>flexible and easy to cover special configurations.
>>
>>v3 -> v4:
>> * redesign framework to make pins dynamically allocated (Arkadiusz)
>> * implement shared pins (Arkadiusz)
>>v2 -> v3:
>> * implement source select mode (Arkadiusz)
>> * add documentation
>> * implementation improvements (Jakub)
>>v1 -> v2:
>> * implement returning supported input/output types
>> * ptp_ocp: follow suggestions from Jonathan
>> * add linux-clk mailing list
>>v0 -> v1:
>> * fix code style and errors
>> * add linux-arm mailing list
>>
>>
>>Arkadiusz Kubalewski (1):
>>  dpll: add dpll_attr/dpll_pin_attr helper classes
>>
>>Vadim Fedorenko (3):
>>  dpll: Add DPLL framework base functions
>>  dpll: documentation on DPLL subsystem interface
>>  ptp_ocp: implement DPLL ops
>>
>> Documentation/networking/dpll.rst  | 271 ++++++++
>> Documentation/networking/index.rst |   1 +
>> MAINTAINERS                        |   8 +
>> drivers/Kconfig                    |   2 +
>> drivers/Makefile                   |   1 +
>> drivers/dpll/Kconfig               |   7 +
>> drivers/dpll/Makefile              |  11 +
>> drivers/dpll/dpll_attr.c           | 278 +++++++++
>> drivers/dpll/dpll_core.c           | 760 +++++++++++++++++++++++
>> drivers/dpll/dpll_core.h           | 176 ++++++
>> drivers/dpll/dpll_netlink.c        | 963 +++++++++++++++++++++++++++++
>> drivers/dpll/dpll_netlink.h        |  24 +
>> drivers/dpll/dpll_pin_attr.c       | 456 ++++++++++++++
>> drivers/ptp/Kconfig                |   1 +
>> drivers/ptp/ptp_ocp.c              | 123 ++--
>> include/linux/dpll.h               | 261 ++++++++
>> include/linux/dpll_attr.h          | 433 +++++++++++++
>> include/uapi/linux/dpll.h          | 263 ++++++++
>> 18 files changed, 4002 insertions(+), 37 deletions(-)  create mode 100644
>>Documentation/networking/dpll.rst  create mode 100644 drivers/dpll/Kconfig
>>create mode 100644 drivers/dpll/Makefile  create mode 100644
>>drivers/dpll/dpll_attr.c  create mode 100644 drivers/dpll/dpll_core.c
>>create mode 100644 drivers/dpll/dpll_core.h  create mode 100644
>>drivers/dpll/dpll_netlink.c  create mode 100644 drivers/dpll/dpll_netlink.h
>>create mode 100644 drivers/dpll/dpll_pin_attr.c  create mode 100644
>>include/linux/dpll.h  create mode 100644 include/linux/dpll_attr.h  create
>>mode 100644 include/uapi/linux/dpll.h
>>
>>--
>>2.27.0
>
>New thread with regard of our yesterday's call.
>
>Is it possible to initialize a multiple output MUX?
>Yes it is. Let's consider 4 input/2 output MUX and DPLL it connects with:
>            +---+   
>          --|   |   
>  +---+     |   |   
>--|   |   --| D |--
>  |   |     | P |   
>--| M |-----| L |--
>  | U |     | L |   
>--| X |-----|   |--
>  |   |     |   |   
>--|   |   --|   |   
>  +---+     +---+  
> 
>Basically dpll pins are initialized and assigned ids, like:
>5 inputs (0-4), 3 outputs (5-7).
>   +---+   
>0--|   |   
>   |   |   
>1--| D |--5
>   | P |   
>2--| L |--6
>   | L |   
>3--|   |--7
>   |   |   
>4--|   |   
>   +---+
>
>Then we would create and register muxed pins with existing dpll pins.
>Each muxed pin is allocated and registered with each parent it can provide
>signal with, like below (number in bracket is parent idx):
>                           +---+   
>                        0--|   |   
>                +---+      |   |   
> 8(2) /  9(3)---|   |   1--| D |--5
>                |   |      | P |   
>10(2) / 11(3)---| M |---2--| L |--6
>                | U |      | L |   
>12(2) / 13(3)---| X |---3--|   |--7
>                |   |      |   |   
>14(2) / 15(3)---|   |   4--|   |   
>                +---+      +---+
>
>Controlling the mux input/output:
>In this case selecting pin #8 would provide its signal into DPLLs input#2 and
>selecting #9 would provide its signal into DPLLs input#3.

Duplication of the mux pin (for example 8,9) seems a bit silly. What if
the mux has 8 outputs? You would have to have 8 pin indexes for each mux
input.

One thing is not clear to me. The mux outputs are fixed or selectable?
I mean, can the outputs be enabled/disabled wired to a specific mux
input?


>
>BR,
>Arkadiusz