linux-kernel - Re: [PATCH 1/3] dt-bindings: ipmi: aspeed: Introduce a v2 binding for KCS

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Message-Id: <fffcd415-0c9e-43ca-8957-b951c2f047b5@www.fastmail.com>
Date:   Fri, 06 Dec 2019 09:49:04 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Rob Herring" <robh+dt@...nel.org>
Cc:     openipmi-developer@...ts.sourceforge.net,
        "Corey Minyard" <minyard@....org>,
        "Mark Rutland" <mark.rutland@....com>,
        "Joel Stanley" <joel@....id.au>, "Arnd Bergmann" <arnd@...db.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-aspeed@...ts.ozlabs.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: ipmi: aspeed: Introduce a v2 binding for KCS



On Fri, 6 Dec 2019, at 04:20, Rob Herring wrote:
> On Wed, Dec 4, 2019 at 11:12 PM Andrew Jeffery <andrew@...id.au> wrote:
> >
> >
> >
> > On Wed, 4 Dec 2019, at 01:01, Rob Herring wrote:
> > > On Tue, Dec 3, 2019 at 6:36 AM Andrew Jeffery <andrew@...id.au> wrote:
> > > >
> > > > The v2 binding utilises reg and renames some of the v1 properties.
> > > >
> > > > Signed-off-by: Andrew Jeffery <andrew@...id.au>
> > > > ---
> > > >  Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt | 20 +++++---
> > > >  1 file changed, 14 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt b/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
> > > > index d98a9bf45d6c..76b180ebbde4 100644
> > > > --- a/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
> > > > +++ b/Documentation/devicetree/bindings/ipmi/aspeed-kcs-bmc.txt
> > > > @@ -1,9 +1,10 @@
> > > > -* Aspeed KCS (Keyboard Controller Style) IPMI interface
> > > > +# Aspeed KCS (Keyboard Controller Style) IPMI interface
> > > >
> > > >  The Aspeed SOCs (AST2400 and AST2500) are commonly used as BMCs
> > > >  (Baseboard Management Controllers) and the KCS interface can be
> > > >  used to perform in-band IPMI communication with their host.
> > > >
> > > > +## v1
> > > >  Required properties:
> > > >  - compatible : should be one of
> > > >      "aspeed,ast2400-kcs-bmc"
> > > > @@ -12,14 +13,21 @@ Required properties:
> > > >  - kcs_chan : The LPC channel number in the controller
> > > >  - kcs_addr : The host CPU IO map address
> > > >
> > > > +## v2
> > > > +Required properties:
> > > > +- compatible : should be one of
> > > > +    "aspeed,ast2400-kcs-bmc-v2"
> > > > +    "aspeed,ast2500-kcs-bmc-v2"
> > > > +- reg : The address and size of the IDR, ODR and STR registers
> > > > +- interrupts : interrupt generated by the controller
> > > > +- slave-reg : The host CPU IO map address
> > >
> > > aspeed,slave-reg
> >
> > I don't agree, as it's not an aspeed-specific behaviour. This property
> > controls where the device appears in the host's LPC IO address space,
> > which is a common problem for any LPC IO device exposed by the BMC
> > to the host.
> 
> Then document it as such. Common properties go into common binding documents.

Fair call.

> 
> > > >  Example:
> > > >
> > > > -    kcs3: kcs3@0 {
> > > > -        compatible = "aspeed,ast2500-kcs-bmc";
> > > > -        reg = <0x0 0x80>;
> > > > +    kcs3: kcs@24 {
> > > > +        compatible = "aspeed,ast2500-kcs-bmc-v2";
> > > > +        reg = <0x24 0x1>, <0x30 0x1>, <0x3c 0x1>;
> > >
> > > What are the other registers in this address space? I'm not so sure
> > > this is an improvement if you end up with a bunch of nodes with single
> > > registers.
> >
> > Put into practice the bindings give the following patch: on the AST2500:
> 
> Okay, that's an unfortunate interleaving, but seems fine.

"Unfortunate" is a good description for the entire register layout of the LPC
slave controller.

I'll send a v2.

Thanks,

Andrew