linux-kernel - Re: [PATCH] watchdog: rzg2l_wdt: Issue a reset before we put the PM clocks

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Message-ID: <CAMuHMdUzNA7CP1zGHSEMK9Jo+76fzEkZ+RXa7ecL0HD4y2gfMg@mail.gmail.com>
Date:   Tue, 15 Nov 2022 09:11:05 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Prabhakar <prabhakar.csengg@...il.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH] watchdog: rzg2l_wdt: Issue a reset before we put the PM clocks

Hi Biju,

On Tue, Nov 15, 2022 at 8:48 AM Biju Das <biju.das.jz@...renesas.com> wrote:
> > > -----Original Message-----
> > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > On Mon, Nov 14, 2022 at 7:42 PM Biju Das
> > <biju.das.jz@...renesas.com> wrote:
> > > > > From: Prabhakar <prabhakar.csengg@...il.com>
> > > > > On RZ/Five SoC it was observed that setting timeout (to say 1
> > sec)
> > > > > wouldn't reset the system. To fix this we make sure we issue a
> > > > > reset before putting the PM clocks to make sure the registers
> > have
> > > > > been
> > > cleared.
> > > > >
> > > > > While at it re-used rzg2l_wdt_stop() in rzg2l_wdt_set_timeout()
> > as
> > > > > we were calling the same functions here.
> > > > >
> > > > > Signed-off-by: Lad Prabhakar
> > > > > <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > ---
> > > > > Note,
> > > > > - This patch has been tested on RZ/G2L, RZ/V2M and RZ/Five.
> > > > > - My initial investigation showed adding the delay after
> > > > > pm_runtime_get_sync()
> > > > >   also fixed this issue.
> > > > > - Do I need add the fixes tag ? what should be the operation
> > PUT-
> > > > > >RESET/RESET->PUT?
> > > >
> > > > It looks like timing issue, None of the previous devices are
> > > > affected by
> > > this.
> > >
> > > To me it looks like the device must be clocked for the reset signal
> > to
> > > be propagated?
> >
> > Yep, provide clk supply for a device, then apply reset.
>
> Maybe we need to make it consistent by taking care of  [1]
>
> Current patch: CLK ON -> apply Reset for V2M.
> [1]:  Apply Reset -> CLK ON for V2M.

Yes, that would also simplify that patch: just add the call to reset?

> [1] https://lore.kernel.org/linux-renesas-soc/CAMuHMdUWbT6VArm9B56VE0yUYWCTm=3vMGrrONSv9cdsQQnhpg@mail.gmail.com/T/#mdb78503524a8f4207f59a40f7ff573e210656988

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds