linux-kernel - Re: [PATCH] arm: dts: am33xx-bone-common: add gpio-line-names

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Message-ID: <20200518142402.GB916914@x1>
Date:   Mon, 18 May 2020 16:24:02 +0200
From:   Drew Fustini <drew@...gleboard.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Benoît Cousson <bcousson@...libre.com>,
        Tony Lindgren <tony@...mide.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>
Subject: Re: [PATCH] arm: dts: am33xx-bone-common: add gpio-line-names

On Mon, May 18, 2020 at 03:34:23PM +0300, Felipe Balbi wrote:
> Linus Walleij <linus.walleij@...aro.org> writes:
> 
> > On Mon, May 18, 2020 at 10:18 AM Felipe Balbi <balbi@...nel.org> wrote:
> >> Linus Walleij <linus.walleij@...aro.org> writes:
> >> >> gpiochip0 - 32 lines:
> >> >>         line   0:   "ethernet"       unused   input  active-high
> >> >>         line   1:   "ethernet"       unused   input  active-high
> >> >
> >> > Why are the ethernet lines not tagged with respective signal name
> >> > when right below the SPI lines are explicitly tagged with
> >> > sclk, cs0 etc?
> >> >
> >> > Ethernet is usually RGMII and has signal names like
> >> > tx_clk, tx_d0, tx_en etc.
> >> >
> >> > Also some lines seem to be tagged with the pin number
> >> > like P9_22, P2_21 below, it seems a bit inconsistent
> >> > to have much information on some pins and very sketchy
> >> > information on some.
> >>
> >> the pin names match the beagle bone documentation and would help users
> >> figure out which pins on the expansion headers match to a gpio signal.

Thank you for pointing this out.  That is my goal with the line names.

> >
> > OK if it is how it looks in the documentation I agree that is what
> > users need, maybe the documentation is confusing but there is not
> > much to do about that.
> 
> the board has two expansion headers, P1 and P2:
> 
> https://github.com/beagleboard/pocketbeagle/wiki/System-Reference-Manual#531_Expansion_Headers
> 
> Pins are always the pin number on the header, hence P2_21 and P1_10 and
> so on.

Just to clarify, the patch was for the BeagleBone {White,Green,Black}
which have P8 and P9 headers.

The PocketBeagle has lower pin count headers labeled P1 and P2.  I do 
plan to submit a patch for am335x-pocketbeagle.dts with the respective
line names, but I wanted to first integrate feedback regarding P8/P9 on
the bone.

thanks,
drew