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 19:59:42 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.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



> -----Original Message-----
> From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> Sent: 14 November 2022 19:56
> 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-
> kernel@...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
> 
> On Mon, Nov 14, 2022 at 7:53 PM Biju Das <biju.das.jz@...renesas.com>
> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > > Sent: 14 November 2022 19:46
> > > 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- kernel@...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.
> >
> > Maybe mention, The resetting of the module is done in wdt_stop
> function.
> >
>     /*
>      * If the watchdog is active, reset the module for updating the
> WDTSET
>      * register by calling rzg2l_wdt_stop() (which internally calls
> reset_control_reset() and pm_runtime_put()

(which internally calls reset_control_reset() to reset the module)

>      * so that it is updated with new timeout values.
>      */