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Date:   Thu, 05 Dec 2019 15:43:39 +1030
From:   "Andrew Jeffery" <andrew@aj.id.au>
To:     "Rob Herring" <robh+dt@kernel.org>
Cc:     openipmi-developer@lists.sourceforge.net,
        "Corey Minyard" <minyard@acm.org>,
        "Mark Rutland" <mark.rutland@arm.com>,
        "Joel Stanley" <joel@jms.id.au>, "Arnd Bergmann" <arnd@arndb.de>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        devicetree@vger.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        linux-aspeed@lists.ozlabs.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: =?UTF-8?Q?Re:_[PATCH_1/3]_dt-bindings:_ipmi:_aspeed:_Introduce_a_v2_bind?=
 =?UTF-8?Q?ing_for_KCS?=
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On Wed, 4 Dec 2019, at 01:01, Rob Herring wrote:
> On Tue, Dec 3, 2019 at 6:36 AM Andrew Jeffery <andrew@aj.id.au> wrote:
> >
> > The v2 binding utilises reg and renames some of the v1 properties.
> >
> > Signed-off-by: Andrew Jeffery <andrew@aj.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.

> 
> >
> >  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:

diff --git a/arch/arm/boot/dts/aspeed-g5.dtsi b/arch/arm/boot/dts/aspeed-g5.dtsi
index e8feb8b66a2f..5d51f469cbf0 100644
--- a/arch/arm/boot/dts/aspeed-g5.dtsi
+++ b/arch/arm/boot/dts/aspeed-g5.dtsi
@@ -399,22 +399,22 @@
                                        #size-cells = <1>;
                                        ranges = <0x0 0x0 0x80>;
 
-                                       kcs1: kcs1@0 {
-                                               compatible = "aspeed,ast2500-kcs-bmc";
+                                       kcs1: kcs@24 {
+                                               compatible = "aspeed,ast2500-kcs-bmc-v2";
+                                               reg = <0x24 0x1>, <0x30 0x1>, <0x3c 0x1>;
                                                interrupts = <8>;
-                                               kcs_chan = <1>;
                                                status = "disabled";
                                        };
-                                       kcs2: kcs2@0 {
-                                               compatible = "aspeed,ast2500-kcs-bmc";
+                                       kcs2: kcs@28 {
+                                               compatible = "aspeed,ast2500-kcs-bmc-v2";
+                                               reg = <0x28 0x1>, <0x34 0x1>, <0x40 0x1>;
                                                interrupts = <8>;
-                                               kcs_chan = <2>;
                                                status = "disabled";
                                        };
-                                       kcs3: kcs3@0 {
-                                               compatible = "aspeed,ast2500-kcs-bmc";
+                                       kcs3: kcs@2c {
+                                               compatible = "aspeed,ast2500-kcs-bmc-v2";
+                                               reg = <0x2c 0x1>, <0x38 0x1>, <0x44 0x1>;
                                                interrupts = <8>;
-                                               kcs_chan = <3>;
                                                status = "disabled";
                                        };
                                };
@@ -428,10 +428,10 @@
                                        #size-cells = <1>;
                                        ranges = <0x0 0x80 0x1e0>;
 
-                                       kcs4: kcs4@0 {
-                                               compatible = "aspeed,ast2500-kcs-bmc";
+                                       kcs4: kcs@94 {
+                                               compatible = "aspeed,ast2500-kcs-bmc-v2";
+                                               reg = <0x94 0x1>, <0x98 0x1>, <0x9c 0x1>;
                                                interrupts = <8>;
-                                               kcs_chan = <4>;
                                                status = "disabled";
                                        };

The aim is to fix these warnings which appear for every aspeed-based devicetree:

        arch/arm/boot/dts/aspeed-g5.dtsi:376.19-381.8: Warning (unit_address_vs_reg): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs1@0: node has a unit name, but no reg property
        arch/arm/boot/dts/aspeed-g5.dtsi:382.19-387.8: Warning (unit_address_vs_reg): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs2@0: node has a unit name, but no reg property
        arch/arm/boot/dts/aspeed-g5.dtsi:388.19-393.8: Warning (unit_address_vs_reg): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs3@0: node has a unit name, but no reg property
        arch/arm/boot/dts/aspeed-g5.dtsi:405.19-410.8: Warning (unit_address_vs_reg): /ahb/apb/lpc@1e789000/lpc-host@80/kcs4@0: node has a unit name, but no reg property
        arch/arm/boot/dts/aspeed-g5.dtsi:376.19-381.8: Warning (unique_unit_address): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs1@0: duplicate unit-address (also used in node /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs2@0)
        arch/arm/boot/dts/aspeed-g5.dtsi:376.19-381.8: Warning (unique_unit_address): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs1@0: duplicate unit-address (also used in node /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs3@0)
        arch/arm/boot/dts/aspeed-g5.dtsi:382.19-387.8: Warning (unique_unit_address): /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs2@0: duplicate unit-address (also used in node /ahb/apb/lpc@1e789000/lpc-bmc@0/kcs3@0)
        arch/arm/boot/dts/aspeed-g5.dtsi:405.19-410.8: Warning (unique_unit_address): /ahb/apb/lpc@1e789000/lpc-host@80/kcs4@0: duplicate unit-address (also used in node /ahb/apb/lpc@1e789000/lpc-host@80/lpc-ctrl@0)

Andrew