linux-kernel - Re: [PATCH v6 08/17] reset: npcm: using syscon instead of device data

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Date:   Thu, 30 Jun 2022 16:53:01 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Tomer Maimon <tmaimon77@...il.com>
Cc:     Avi Fishman <avifishman70@...il.com>,
        Tali Perry <tali.perry1@...il.com>,
        Joel Stanley <joel@....id.au>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Olof Johansson <olof@...om.net>,
        Jiri Slaby <jirislaby@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Vinod Koul <vkoul@...nel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>,
        Robert Hancock <robert.hancock@...ian.com>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        Lubomir Rintel <lkundrak@...sk>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        LINUXWATCHDOG <linux-watchdog@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 08/17] reset: npcm: using syscon instead of device
 data

On Do, 2022-06-30 at 14:20 +0300, Tomer Maimon wrote:
> Hi Philipp,
> 
> Thanks for your comment.
> 
> On Thu, 30 Jun 2022 at 13:59, Philipp Zabel <p.zabel@...gutronix.de> wrote:
> > 
> > Hi Tomer,
> > 
> > On Do, 2022-06-30 at 13:35 +0300, Tomer Maimon wrote:
> > Using syscon device tree property instead of device data to handle the
> > NPCM general control registers.
> > 
> > In case the syscon not found the code still search for nuvoton,npcm750-gcr
> > to support DTS backward compatibility.
> > 
> > Signed-off-by: Tomer Maimon <tmaimon77@...il.com>
> > ---
> >  drivers/reset/reset-npcm.c | 17 ++++++++---------
> >  1 file changed, 8 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/reset/reset-npcm.c b/drivers/reset/reset-npcm.c
> > index 2ea4d3136e15..431ff2b602c5 100644
> > --- a/drivers/reset/reset-npcm.c
> > +++ b/drivers/reset/reset-npcm.c
> > @@ -138,8 +138,7 @@ static int npcm_reset_xlate(struct reset_controller_dev *rcdev,
> >  }
> > 
> > 
> >  static const struct of_device_id npcm_rc_match[] = {
> > -       { .compatible = "nuvoton,npcm750-reset",
> > -               .data = (void *)"nuvoton,npcm750-gcr" },
> > +       { .compatible = "nuvoton,npcm750-reset"},
> > 
> > Add a space.                                  ^^
> Will modify in V7
> > 
> >         { }
> >  };
> > 
> > 
> > @@ -155,15 +154,15 @@ static int npcm_usb_reset(struct platform_device *pdev, struct npcm_rc_data *rc)
> >         u32 ipsrst1_bits = 0;
> >         u32 ipsrst2_bits = NPCM_IPSRST2_USB_HOST;
> >         u32 ipsrst3_bits = 0;
> > -       const char *gcr_dt;
> > 
> > 
> > -       gcr_dt = (const char *)
> > -       of_match_device(dev->driver->of_match_table, dev)->data;
> > -
> > -       gcr_regmap = syscon_regmap_lookup_by_compatible(gcr_dt);
> > +       gcr_regmap = syscon_regmap_lookup_by_phandle(dev->of_node, "nuvoton,sysgcr");
> >         if (IS_ERR(gcr_regmap)) {
> > -               dev_err(&pdev->dev, "Failed to find %s\n", gcr_dt);
> > -               return PTR_ERR(gcr_regmap);
> > +               dev_warn(&pdev->dev, "Failed to find nuvoton,sysgcr search for nuvoton,npcm750-gcr for Poleg backward compatibility");
> > 
> > Is this warning useful to the user? Maybe add suggestion like "please
> > update the device tree". Also there is no further message if
> > nuvoton,npcm750-gcr is found and all is well.
> 
> O.K.
> I think about two options:
> 
> 1. Modify the message "Failed to find nuvoton,sysgcr property, please
> update the device tree\n Search for nuvoton,npcm750-gcr for Poleg
> backward compatibility"

I would replace "Search for" with "Using"
The second line probably should be dev_info() level.

> OR
> 
> 2.
>         if (IS_ERR(rc->gcr_regmap)) {
>                 dev_warn(&pdev->dev, "Failed to find nuvoton,sysgcr
> please update the device tree");
>                 rc->gcr_regmap =
> syscon_regmap_lookup_by_compatible("nuvoton,npcm750-gcr");
>                 if (IS_ERR(rc->gcr_regmap)) {
>                         dev_err(&pdev->dev, "Failed to find
> nuvoton,npcm750-gcr");
>                         return PTR_ERR(rc->gcr_regmap);
>                 }
>                  dev_info(&pdev->dev, "found nuvoton,npcm750-gcr for
> Poleg backward compatibility");
>         }
> 
> The only problem that I have with option 2 is if our customers will
> use the latest reset driver and they will not update their device tree
> they will see all the time the dev_info message.
> 
> What do you think?

I'm fine with either. With the "please update DT" prompt it's clear how
to get rid of the warning.

regards
Philipp