RE: [PATCH v1] ARM: dts: aspeed: Adding Facebook Bletchley BMC

["Howard Chiu (邱冠睿)" <Howard.Chiu@quantatw.com>]

> > > Is this board using 64MB or 128MB modules?  Many of the newer systems
> > > have been
> > > starting to use 128MB.  I just want to confirm this is correct.
> > 1Gb SPI flash, MX66L1G45GMI-08G
> 
> 1Gb = 1024Mb / 8 = 128MB, right?  Shouldn't we use the 128MB layout?
Will be fixed in the next patch
> 
> > > > +	sled0_ioexp: pca9539@76 {
> > > > +		compatible = "nxp,pca9539";
> > > > +		reg = <0x76>;
> > > > +		#address-cells = <1>;
> > > > +		#size-cells = <0>;
> > > > +		gpio-controller;
> > > > +		#gpio-cells = <2>;
> > > > +
> > > > +		gpio-line-names =
> > > > +
> > > 	"","SLED0_BMC_CCG5_INT","SLED0_INA230_ALERT","SLED0_P12V_STBY_
> > > ALERT",
> > > > +
> > > 	"SLED0_SSD_ALERT","SLED0_MS_DETECT","SLED0_MD_REF_PWM","",
> > > > +
> > > 	"SLED0_MD_STBY_RESET","SLED0_MD_IOEXP_EN_FAULT","SLED0_MD_D
> > > IR","SLED0_MD_DECAY",
> > > > +
> > > 	"SLED0_MD_MODE1","SLED0_MD_MODE2","SLED0_MD_MODE3","SLED
> > > 0_AC_PWR_EN";
> > >
> > > In general, in OpenBMC, we have a preference for the GPIOs to not be
> > > schematic
> > > names but to be named based on their [software-oriented] function.
> Please
> > > take
> > > a look at:
> > >
> > >
> > >
> https://github.com/openbmc/docs/blob/master/designs/device-tree-gpio-na
> > > ming.md
> > >
> > > Any function you see that isn't documented there we should try to get
> > > documented
> > > before fixing the GPIO name to match it.
> > >
> > I intend to delete them for now if I have to document them first, because
> > most of them are platform-specific GPIO, not for general purpose and also
> not
> > suitable to current OpenBMC.
> > For example, OpenBMC believes there is only one GPIO to be used to power
> on
> > the chassis, but Bletchley has six.
> > I define gpio-line-names for gpioset/geioget/phosphor-multi-gpio-monitor
> > usage, and they can be replaced with gpiochip number and offset instead.
> > The disadvantage is that they won't be human-friendly when TEs develop
> their tool to test these GPIOs.
> > > > +		gpio-line-names =
> > > > +
> 	"SLED0_EMBER_LED","SLED0_BLUE_LED","SLED0_RST_IOEXP","",
> 
> Deleting them entirely sounds even less desirable.  If these were just for
> humans, then having a schematic name is better than nothing.  But when you
> suggest their usage to be "TEs develop their tool to test these GPIOs" that
> seems to indicate this becomes ABI and we want stable, documented names,
> to
> limit the churn on users.
> 
> I don't believe the gpiochip/pin numbers are considered stable ABI.  Our
> team
> has previously had to do an abstraction between 4.x and 5.x kernel because of
> changes in that space.
> 
> My initial preference would be that you leave them in as schematic names, for
> human purposes, until you start using them in code at which point they should
> be
> well-documented and using the style we've set out in the document above.
> 
> Re: "OpenBMC believes there is only one GPIO to be used to power on the
> chassis,
> but Bletchley has six."... This does not make it system-specific.  Yosemite-v2
> has 4 independently managed systems, with their own power sequencing.
> There
> should be work going on by that team to expand the GPIO documentation to
> cover N
> sub-chassis as well; it just might be that you are ahead of them in documenting
> it.
> 
> It should be trivial to expand the `power-chassis-control` and
> `power-chassis-good` documentation to support sub-chassis.  I can do this for
> you if you need.  Many of your GPIOs were related to LEDs which are also
> already
> covered by this doc (except might need minor wording for sub-chassis as well).
> Can you let me know which other GPIO functions you think you'll need that
> aren't
> already in that document and we can work to get them added?
I don't have enough experience with LF-OpenBMC so that I tried not to modify any present documentation since I don't know how to make them reliable to LF-OpenBMC community for common usage 
If you have idea to expand the naming rule, I will follow it.

For LEDs, they are not really necessary because led-manager only used the node name. gpio-lines-name is only human-friendly for debug purpose when user uses GPIO tool, which make them easier to control GPIO directly.
In general purpose, controlling LED via D-Bus is better. 
> 
> > > > +&i2c13 {
> > > > +	multi-master;
> > > > +	aspeed,hw-timeout-ms = <1000>;
> > > > +	status = "okay";
> > > > +};
> > >
> > > Was this intentional to have defined a multi-master bus with nothing on it?
> > There is a OCP debug card which is a hot plugging device.
> > We only need to specify this bus with "multi-mater" property for IPMB
> support.
> 
> Got it.
> 
> --
> Patrick Williams