linux-kernel - Re: [PATCH] ARM: dts: aspeed: Add AMD DaytonaX BMC

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Message-ID: <CACPK8Xcc6Nem00zZdGmHF=U4T2O90aL+_vKO4YmAqSW9wKeegA@mail.gmail.com>
Date:   Tue, 16 Nov 2021 06:07:55 +0000
From:   Joel Stanley <joel@....id.au>
To:     Konstantin Aladyshev <aladyshev22@...il.com>,
        Patrick Williams <patrick@...cx.xyz>
Cc:     Supreeth Venkatesh <supreeth.venkatesh@....com>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        SoC Team <soc@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Andrew Jeffery <andrew@...id.au>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-aspeed <linux-aspeed@...ts.ozlabs.org>,
        Andrew Geissler <geissonator@...oo.com>
Subject: Re: [PATCH] ARM: dts: aspeed: Add AMD DaytonaX BMC

On Wed, 27 Oct 2021 at 10:59, Konstantin Aladyshev
<aladyshev22@...il.com> wrote:
>
> Thanks for the comments. Can I ask you some questions about this
> `device-tree-gpio-naming.md`?
>
> 1) First of all in my naming I've tried to use naming scheme the same
> as the EthanolX CRB DTS currently has
> (https://github.com/torvalds/linux/blob/d25f27432f80a800a3592db128254c8140bd71bf/arch/arm/boot/dts/aspeed-bmc-amd-ethanolx.dts#L102).
> Do you want me to change GPIO naming in the EthanolX CRB as well?

Yeah, that would make sense.

> 2) Also this naming comes from the signal names in the board
> schematics. This way it is clear to check schematics vs DTS. If we use
> this OpenBMC naming style, we will lose that correspondence. Is it
> really good?

This is a good point. The preference is to use human readable names
over the schematic net. I can see cases where this would be worse, but
hopefully on balance it results in consistent naming between machines.

> 3) In the initial version of the DTS file I've supplied only a minimal
> set of GPIO, that are used by OpenBMC. GPIOs for x86-power-control app
> and led id/fault gpios. With renaming these GPIOs I'm only sure about
> these GPIOs:
>
> FAULT_LED                  - led-fault
> CHASSIS_ID_BTN        - led-identify
>
> What about the rest? For example the document doesn't really state
> what the *-button postfix states? Is it for asserting or monitoring
> buttons? How should I name these signals?
>
> ASSERT_BMC_READY
> ASSERT_RST_BTN
> ASSERT_PWR_BTN
>
> MON_P0_RST_BTN
> MON_P0_PWR_BTN
> MON_P0_PWR_GOOD
> MON_PWROK
>
> Can you help me with those?

Patrick, do you have thoughts here?

>
> 4) And what should I do to the board GPIO signals that OpenBMC doesn't
> use? If you look at the EthanolX CRB DTS
> (https://github.com/torvalds/linux/blob/d25f27432f80a800a3592db128254c8140bd71bf/arch/arm/boot/dts/aspeed-bmc-amd-ethanolx.dts#L102)
> it has a ton of GPIOs. Should they be renamed to this OpenBMC style as
> well? Or can they be named exactly like in the schematics?

That's up to you.

>
> I've also CCed original author of the `device-tree-gpio-naming.md`
> document Andrew Geissler. Andrew, can you please provide your opinion
> on the subject?

I've also added Patrick, who is helping review this document.

Cheers,

Joel

>
> Best regards,
> Konstantin Aladyshev
>
> On Wed, Oct 27, 2021 at 12:03 AM Joel Stanley <joel@....id.au> wrote:
> >
> > Hello Konstantin,
> >
> > On Tue, 26 Oct 2021 at 20:01, Konstantin Aladyshev
> > <aladyshev22@...il.com> wrote:
> > >
> > > Add initial version of device tree for the BMC in the AMD DaytonaX
> > > platform.
> > >
> > > AMD DaytonaX platform is a customer reference board (CRB) with an
> > > Aspeed ast2500 BMC manufactured by AMD.
> > >
> > > Signed-off-by: Konstantin Aladyshev <aladyshev22@...il.com>
> >
> > This looks good. I have one comment about the GPIOs below.
> >
> > > +&gpio {
> > > +       status = "okay";
> > > +       gpio-line-names =
> > > +       /*A0-A7*/       "","","FAULT_LED","","","","","",
> > > +       /*B0-B7*/       "","","","","","","","",
> > > +       /*C0-C7*/       "CHASSIS_ID_BTN","","","","","","","",
> > > +       /*D0-D7*/       "","","ASSERT_BMC_READY","","","","","",
> > > +       /*E0-E7*/       "MON_P0_RST_BTN","ASSERT_RST_BTN","MON_P0_PWR_BTN","ASSERT_PWR_BTN","",
> > > +                       "MON_P0_PWR_GOOD","MON_PWROK","",
> >
> > For systems that will run openbmc, we try to use naming conventions
> > from this document:
> >
> > https://github.com/openbmc/docs/blob/master/designs/device-tree-gpio-naming.md
> >
> > If a GPIO is missing from that doc I encourage you to add it.