linux-kernel - Re: [PATCH] arm: dts: Add am335x-boneblack-pps.dts

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Date:   Fri, 28 Apr 2023 15:53:16 -0500
From:   Robert Nelson <robertcnelson@...il.com>
To:     Julien Panis <jpanis@...libre.com>
Cc:     arnd@...db.de, olof@...om.net, soc@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, tony@...mide.com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org
Subject: Re: [PATCH] arm: dts: Add am335x-boneblack-pps.dts

On Fri, Apr 28, 2023 at 9:44 AM Robert Nelson <robertcnelson@...il.com> wrote:
>
> On Fri, Apr 28, 2023 at 6:00 AM Julien Panis <jpanis@...libre.com> wrote:
> >
> > From: Lokesh Vutla <lokeshvutla@...com>
> >
> > Add a new am335x-boneblack-pps.dts that can be used to configure TIMER7
> > in PWM mode. This PWM signal can be used as a PPS signal when
> > synchronized to PTP clock. Typically this synchronization is done by a
> > userspace program. This PPS signal can be observed on pin P8.8.
> >
> > Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
> > Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
> > Signed-off-by: Adrien Ricciardi <aricciardi@...libre.com>
> > Signed-off-by: Julien Panis <jpanis@...libre.com>
> > ---
> >  arch/arm/boot/dts/Makefile                 |  1 +
> >  arch/arm/boot/dts/am335x-boneblack-pps.dts | 25 ++++++++++++++++++++++
> >  2 files changed, 26 insertions(+)
> >  create mode 100644 arch/arm/boot/dts/am335x-boneblack-pps.dts
> >
> > diff --git a/arch/arm/boot/dts/Makefile b/arch/arm/boot/dts/Makefile
> > index efe4152e5846..d74158aae72d 100644
> > --- a/arch/arm/boot/dts/Makefile
> > +++ b/arch/arm/boot/dts/Makefile
> > @@ -939,6 +939,7 @@ dtb-$(CONFIG_SOC_AM33XX) += \
> >         am335x-base0033.dtb \
> >         am335x-bone.dtb \
> >         am335x-boneblack.dtb \
> > +       am335x-boneblack-pps.dtb \
> >         am335x-boneblack-wireless.dtb \
> >         am335x-boneblue.dtb \
> >         am335x-bonegreen.dtb \
> > diff --git a/arch/arm/boot/dts/am335x-boneblack-pps.dts b/arch/arm/boot/dts/am335x-boneblack-pps.dts
> > new file mode 100644
> > index 000000000000..88d2bc3fd759
> > --- /dev/null
> > +++ b/arch/arm/boot/dts/am335x-boneblack-pps.dts
> > @@ -0,0 +1,25 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2023 Texas Instruments Incorporated - http://www.ti.com/
> > + */
> > +
> > +#include "am335x-boneblack.dts"
> > +
> > +&am33xx_pinmux {
> > +       pwm7_pins: pinmux_pwm7_pins {
> > +               pinctrl-single,pins = <
> > +                       AM33XX_PADCONF(AM335X_PIN_GPMC_OEN_REN, PIN_OUTPUT_PULLDOWN, MUX_MODE2)
> > +               >;
> > +       };
> > +};
> > +
> > +/{
> > +       pwm7: dmtimer-pwm7 {
> > +               compatible = "ti,omap-dmtimer-pwm";
> > +               pinctrl-names = "default";
> > +               pinctrl-0 = <&pwm7_pins>;
> > +               #pwm-cells = <3>;
> > +               ti,timers = <&timer7>;
> > +               ti,clock-source = <0x00>; /* timer_sys_ck */
> > +       };
> > +};
>
> I know this commit is pretty small, but mainline now has overlay support:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0fff0e49d72a53c51d8903fbadb2e6a84e531c4a
>
> At what point do we finally merge in the many dozen *BeagleBone*
> overlays, or do we still wait for :
> https://lore.kernel.org/lkml/20220328000915.15041-1-ansuelsmth@gmail.com/

OH SIde note, #2... thanks @Nishanth Menon !

We do have this example:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8e01fb15b8157a825d309ea2598b494dd81a7b42

So instead of `am335x-boneblack-pps.dtb` it could be: ....
am335x-bone-dmtimer-pwm7.dtbo or even am335x-dmtimer-pwm7.dtbo ?

Thoughts?

-- 
Robert Nelson
https://rcn-ee.com/