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

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Date:   Mon, 14 Nov 2022 19:45:38 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Biju Das <biju.das.jz@...renesas.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        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,

Thank you for the review.

On Mon, Nov 14, 2022 at 6:42 PM Biju Das <biju.das.jz@...renesas.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Prabhakar <prabhakar.csengg@...il.com>
> > Sent: 14 November 2022 18:09
> > To: Geert Uytterhoeven <geert+renesas@...der.be>; Wim Van Sebroeck
> > <wim@...ux-watchdog.org>; Guenter Roeck <linux@...ck-us.net>; Philipp Zabel
> > <p.zabel@...gutronix.de>; linux-watchdog@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org; linux-renesas-soc@...r.kernel.org;
> > Prabhakar <prabhakar.csengg@...il.com>; Biju Das
> > <biju.das.jz@...renesas.com>; Fabrizio Castro
> > <fabrizio.castro.jz@...esas.com>; Prabhakar Mahadev Lad <prabhakar.mahadev-
> > lad.rj@...renesas.com>
> > Subject: [PATCH] watchdog: rzg2l_wdt: Issue a reset before we put the PM
> > clocks
> >
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.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.
>
yep.

> >   in case we need the tag is:
> >   Fixes: 4055ee81009e6 ("watchdog: rzg2l_wdt: Add set_timeout callback")
> > ---
> >  drivers/watchdog/rzg2l_wdt.c | 7 ++-----
> >  1 file changed, 2 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
> > index 00438ceed17a..d1271cc7750f 100644
> > --- a/drivers/watchdog/rzg2l_wdt.c
> > +++ b/drivers/watchdog/rzg2l_wdt.c
> > @@ -115,16 +115,14 @@ static int rzg2l_wdt_stop(struct watchdog_device *wdev)
> > {
> >       struct rzg2l_wdt_priv *priv = watchdog_get_drvdata(wdev);
> >
> > -     pm_runtime_put(wdev->parent);
> >       reset_control_reset(priv->rstc);
> > +     pm_runtime_put(wdev->parent);
> >
> >       return 0;
> >  }
> >
> >  static int rzg2l_wdt_set_timeout(struct watchdog_device *wdev, unsigned int
> > timeout)  {
> > -     struct rzg2l_wdt_priv *priv = watchdog_get_drvdata(wdev);
> > -
> >       wdev->timeout = timeout;
> >
> >       /*
> > @@ -132,8 +130,7 @@ static int rzg2l_wdt_set_timeout(struct watchdog_device
> > *wdev, unsigned int time
> >        * register so that it is updated with new timeout values.
> >        */
>
>
> Maybe update the comment above with new code change.
>
    /*
     * If the watchdog is active, reset the module for updating the WDTSET
     * register so that it is updated with new timeout values.
     */

The above existing comment holds good with this code change. If you
prefer something else please let me know I'll update it accordingly.

Cheers,
Prabhakar