linux-kernel - Re: [PATCH v2 14/17] riscv: dts: microchip: add fpga fabric section to icicle kit

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Message-ID: <65370401-1d93-f869-9b85-cdc4d211fcba@microchip.com>
Date:   Wed, 12 Jan 2022 09:38:04 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <geert@...ux-m68k.org>
CC:     <linus.walleij@...aro.org>, <bgolaszewski@...libre.com>,
        <robh+dt@...nel.org>, <jassisinghbrar@...il.com>,
        <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <a.zummo@...ertech.it>,
        <alexandre.belloni@...tlin.com>, <broonie@...nel.org>,
        <gregkh@...uxfoundation.org>, <thierry.reding@...il.com>,
        <u.kleine-koenig@...gutronix.de>, <lee.jones@...aro.org>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        <linux-crypto@...r.kernel.org>, <linux-rtc@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <krzysztof.kozlowski@...onical.com>, <bin.meng@...driver.com>,
        <heiko@...ech.de>, <Lewis.Hanly@...rochip.com>,
        <Daire.McNamara@...rochip.com>, <Ivan.Griffin@...rochip.com>,
        <atishp@...shpatra.org>
Subject: Re: [PATCH v2 14/17] riscv: dts: microchip: add fpga fabric section
 to icicle kit

On 17/12/2021 16:00, Geert Uytterhoeven wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Hi Conor,
> 
> On Fri, Dec 17, 2021 at 4:32 PM <Conor.Dooley@...rochip.com> wrote:
>> On 17/12/2021 13:43, Geert Uytterhoeven wrote:
>>> On Fri, Dec 17, 2021 at 10:33 AM <conor.dooley@...rochip.com> wrote:
>>>> From: Conor Dooley <conor.dooley@...rochip.com>
>>>>
>>>> Split the device tree for the Microchip MPFS into two sections by adding
>>>> microchip-mpfs-fabric.dtsi, which contains peripherals contained in the
>>>> FPGA fabric.
>>>>
>>>> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
>>>
>>> Thanks for your patch!
>>>
>>>> --- /dev/null
>>>> +++ b/arch/riscv/boot/dts/microchip/microchip-mpfs-fabric.dtsi
>>>> @@ -0,0 +1,13 @@
>>>> +// SPDX-License-Identifier: (GPL-2.0 OR MIT)
>>>> +/* Copyright (c) 2020-2021 Microchip Technology Inc */
>>>> +
>>>> +/ {
>>>> +       corePWM0: pwm@...00000 {
>>>> +               compatible = "microchip,corepwm";
>>>> +               reg = <0x0 0x41000000 0x0 0xF0>;
>>>> +               microchip,sync-update = /bits/ 8 <0>;
>>>> +               #pwm-cells = <2>;
>>>> +               clocks = <&clkcfg CLK_FIC3>;
>>>> +               status = "disabled";
>>>> +       };
>>>
>>> I'm wondering if these should be grouped under a "fabric" subnode,
>>> like we have an "soc" subnode for on-SoC devices? Rob?
>>>
>>> BTW, do you already have a naming plan for different revisions of
>>> FPGA fabric cores?
>> Not yet (assuming you mean specifically how we will handle it in the
>> device tree) - although i was talking to someone about it yesterday.
>> It's possible that we might handle that via a register, but if you have
>> a suggestion or some precedence that you're aware of that would be useful.
>>
>> The actual naming convention of the IP cores themselves, yeah. I will
>> dig it up for you on Monday.
> 
> I meant what if corepwm is enhanced, and how to detect that?
> 
Looks like "microchip,core<name>-N" is the plan. More recent IP cores 
have a register from which the version number can be read but that isnt 
(and wont be) the case for all versions.
Where this register does exist, we will use it & if not fall back onto 
the compat. string.
> SiFive uses an integer version number, even for hard cores[1].
> OpenCores uses an "-rtlsvnN" suffix (isn't svn dead? ;-)
At least here, "hardware" people seem to be a fan of it still (sadly?)
> No idea what e.g. LiteX and Microwatt are planning. >
> [1] Documentation/devicetree/bindings/sifive/sifive-blocks-ip-versioning.txt
> 
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds