RE: [PATCH 3/3] arm64: dts: renesas: rzg2l-smarc: Enable MTU3a counter using DT overlay

From: Biju Das <biju.das.jz@bp.renesas.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Magnus Damm <magnus.damm@gmail.com>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: RE: [PATCH 3/3] arm64: dts: renesas: rzg2l-smarc: Enable MTU3a counter using DT overlay
Date: Fri, 21 Apr 2023 07:45:43 +0000	[thread overview]
Message-ID: <OS0PR01MB5922D327CD46A5BC183656F186609@OS0PR01MB5922.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <CAMuHMdV4LOsJf+bnb8XRQo5_1Mdby1EArSdnW2oY6t0_yR1Oug@mail.gmail.com>

Hi Geert,

> > > > > Enable MTU3a counter using DT overlay
> > > > >
> > > > > Hi Biju,
> > > > >
> > > > > On Mon, Apr 17, 2023 at 11:02 AM Biju Das
> > > > > <biju.das.jz@bp.renesas.com>
> > > > > wrote:
> > > > > > Enable mtu3 node using dt overlay and disable scif2 node and
> > > > > > delete {sd1_mux,sd1_mux_uhs} nodes as the pins are shared with
> > > > > > mtu3 external clock input pins and Z phase signal(MTIOC1A).
> > > > > >
> > > > > > Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> > >
> > > > > > --- /dev/null
> > > > > > +++ b/arch/arm64/boot/dts/renesas/rzg2l-smarc-pmod.dtso
> > > > > > @@ -0,0 +1,43 @@
> > > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > > +/*
> > > > > > + * Device Tree Source for the RZ/{G2L,V2L} SMARC EVK PMOD
> > > > > > +parts
> > > > > > + *
> > > > > > + * Copyright (C) 2023 Renesas Electronics Corp.
> > > > > > + */
> > > > > > +
> > > > > > +/dts-v1/;
> > > > > > +/plugin/;
> > > > > > +
> > > > > > +#include <dt-bindings/pinctrl/rzg2l-pinctrl.h>
> > > > > > +
> > > > > > +&mtu3 {
> > > > > > +       pinctrl-0 = <&mtu3_pins>;
> > > > > > +       pinctrl-names = "default";
> > > > > > +
> > > > > > +       status = "okay";
> > > > > > +};
> > > > > > +
> > > > > > +&pinctrl {
> > > > > > +       mtu3_pins: mtu3 {
> > > > > > +               mtu3-zphase-clk {
> > > > > > +                       pinmux = <RZG2L_PORT_PINMUX(19, 0,
> > > > > > +3)>; /* MTIOC1A
> > > > > */
> > > > > > +               };
> > > > >
> > > > > Unless I'm missing something, this signal is not available on
> > > > > the PMOD connector?
> > > >
> > > > Yes, it is not available on the PMOD connector. SD card detection
> > > > signal, is muxed with MTIOC1A (Z Phase signal). So for counter use
> > > > case, we use it as MTIOC1A pins.
> > >
> > > As the signal is not available on the PMOD connector, can't you just
> > > ignore the Z Phase signal, and keep the SD card CD signal available
> instead?
> >
> >
> > Some customers are using Z phase signal in their product to clear the
> counter.
> > Maybe we define a macro in overlay, by default Z phase signal is disabled.
> >
> > Is it ok?
> >
> > Note:-
> > I use SD card removal/insert which changes the Z phase signal level
> > for clearing the counter.
> 
> After giving this some more thought, I don't think this overlay belongs
> upstream: it does not just enable hardware support, but provides a way to
> test hardware, by redefining the meaning of signals on the PMOD interface.
> 

> Do you agree?

Like any other PMOD interface, we can test real counter device with PMOD interface[1]

https://www.mouser.co.uk/ProductDetail/Alps-Alpine/EC11E15244B2?qs=m0BA540hBPfDpUEkDmFV5A%3D%3D

I have used this device for testing as well, later I switched to gpios for generating phase signals.

> 
> I can add (a future version of) the overlay file (without the build
> glue) to my topic/renesas-overlays branch[1], though.
> 

Without any hassles, if anyone wants to test counter interface using RZ/{G2L,G2LC,G2UL,Five, V2L}
SMARC EVK then I am ok for adding it to topic/renesas-overlays branch.

I believe the current overlay patch will provide that flexibility.

Cheers,
Biju