linux-kernel - RE: [PATCH 2/2] watchdog: rzg2l_wdt: Handle TYPE-B reset for RZ/V2M

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Message-ID: <TYWPR01MB87757FCB3CDA549DB4DC4743C2C19@TYWPR01MB8775.jpnprd01.prod.outlook.com>
Date:   Mon, 16 Jan 2023 16:24:57 +0000
From:   Fabrizio Castro <fabrizio.castro.jz@...esas.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Biju Das <biju.das.jz@...renesas.com>,
        "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jacopo Mondi <jacopo@...ndi.org>
Subject: RE: [PATCH 2/2] watchdog: rzg2l_wdt: Handle TYPE-B reset for RZ/V2M

Hi Geert,

Thanks for your reply!

> 
> Hi Fabrizio,
> 
> On Mon, Jan 16, 2023 at 5:18 PM Fabrizio Castro
> <fabrizio.castro.jz@...esas.com> wrote:
> > > On Thu, Nov 17, 2022 at 12:49 PM Fabrizio Castro
> > > <fabrizio.castro.jz@...esas.com> wrote:
> > > > As per section 48.4 of the HW User Manual, IPs in the RZ/V2M
> > > > SoC need either a TYPE-A reset sequence or a TYPE-B reset
> > > > sequence. More specifically, the watchdog IP needs a TYPE-B
> > > > reset sequence.
> > > >
> > > > If the proper reset sequence isn't implemented, then resetting
> > > > IPs may lead to undesired behaviour. In the restart callback of
> > > > the watchdog driver the reset has basically no effect on the
> > > > desired funcionality, as the register writes following the reset
> > > > happen before the IP manages to come out of reset.
> > > >
> > > > Implement the TYPE-B reset sequence in the watchdog driver to
> > > > address the issues with the restart callback on RZ/V2M.
> > > >
> > > > Fixes: ec122fd94eeb ("watchdog: rzg2l_wdt: Add rzv2m support")
> > > > Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
> > >
> > > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > >
> > > Perhaps this logic can be incorporated into the RZ/V2M reset
> controller
> > > driver later, so reset consumers don't have to care about TYPE-A
> and
> > > TYPE-B reset, but can just call reset_control_reset()?
> > > I understand that's not gonna be easy, as it needs to know about
> the
> > > relation between resets and clocks, and how to handle both cases
> (clock
> > > (not) switched off) for TYPE-B resets.
> >
> > Yeah, we have been thinking about dealing with this in the reset
> controller
> > driver, but as you pointed out it's not going to be simple, and
> therefore
> > it'll take some time. This change will guarantee the correct
> behaviour of
> > the watchdog for now, we'll tackle the larger issue later on, if
> that's okay
> > with you.
> 
> Fine for me.

Awesome, thanks for that.

Cheers,
Fab

> 
> 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