linux-kernel - Re: [PATCH 1/2] watchdog: s3c2410_wdt: Use Use devm_clk_get[_optional]

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Date:   Sun, 5 Mar 2023 12:15:00 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] watchdog: s3c2410_wdt: Use Use
 devm_clk_get[_optional]_enabled() helpers

Hello Guenter,

On Sat, Mar 04, 2023 at 02:10:47PM -0800, Guenter Roeck wrote:
> On 3/4/23 13:46, Christophe JAILLET wrote:
> > Le 04/03/2023 à 17:56, Guenter Roeck a écrit :
> > > The devm_clk_get[_optional]_enabled() helpers:
> > >      - call devm_clk_get[_optional]()
> > >      - call clk_prepare_enable() and register what is needed in order to
> > >        call clk_disable_unprepare() when needed, as a managed resource.
> > > 
> > > This simplifies the code and avoids the calls to clk_disable_unprepare().
> > > 
> > > While at it, use dev_err_probe consistently, and use its return value
> > > to return the error code.
> > > 
> > > Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > > ---
> > >   drivers/watchdog/s3c2410_wdt.c | 45 +++++++---------------------------
> > >   1 file changed, 9 insertions(+), 36 deletions(-)
> > > 
> > > diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> > > index 200ba236a72e..a1fcb79b0b7c 100644
> > > --- a/drivers/watchdog/s3c2410_wdt.c
> > > +++ b/drivers/watchdog/s3c2410_wdt.c
> > > @@ -661,35 +661,17 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
> > >       if (IS_ERR(wdt->reg_base))
> > >           return PTR_ERR(wdt->reg_base);
> > > -    wdt->bus_clk = devm_clk_get(dev, "watchdog");
> > > -    if (IS_ERR(wdt->bus_clk)) {
> > > -        dev_err(dev, "failed to find bus clock\n");
> > > -        return PTR_ERR(wdt->bus_clk);
> > > -    }
> > > -
> > > -    ret = clk_prepare_enable(wdt->bus_clk);
> > > -    if (ret < 0) {
> > > -        dev_err(dev, "failed to enable bus clock\n");
> > > -        return ret;
> > > -    }
> > > +    wdt->bus_clk = devm_clk_get_enabled(dev, "watchdog");
> > > +    if (IS_ERR(wdt->bus_clk))
> > > +        return dev_err_probe(dev, PTR_ERR(wdt->bus_clk), "failed to get bus clock\n");
> > >       /*
> > >        * "watchdog_src" clock is optional; if it's not present -- just skip it
> > >        * and use "watchdog" clock as both bus and source clock.
> > >        */
> > > -    wdt->src_clk = devm_clk_get_optional(dev, "watchdog_src");
> > > -    if (IS_ERR(wdt->src_clk)) {
> > > -        dev_err_probe(dev, PTR_ERR(wdt->src_clk),
> > > -                  "failed to get source clock\n");
> > > -        ret = PTR_ERR(wdt->src_clk);
> > > -        goto err_bus_clk;
> > > -    }
> > > -
> > > -    ret = clk_prepare_enable(wdt->src_clk);
> > > -    if (ret) {
> > > -        dev_err(dev, "failed to enable source clock\n");
> > > -        goto err_bus_clk;
> > > -    }
> > > +    wdt->src_clk = devm_clk_get_optional_enabled(dev, "watchdog_src");
> > > +    if (IS_ERR(wdt->src_clk))
> > > +        return dev_err_probe(dev, PTR_ERR(wdt->src_clk), "failed to get source clock\n");
> > >       wdt->wdt_device.min_timeout = 1;
> > >       wdt->wdt_device.max_timeout = s3c2410wdt_max_timeout(wdt);
> > > @@ -710,7 +692,7 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
> > >                    S3C2410_WATCHDOG_DEFAULT_TIME);
> > >           } else {
> > >               dev_err(dev, "failed to use default timeout\n");
> > > -            goto err_src_clk;
> > > +            return ret;
> > 
> > Hi,
> > 
> > Nit: this also could be "return dev_err_probe()"
> > 
> > >           }
> > >       }
> > > @@ -718,7 +700,7 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
> > >                      pdev->name, pdev);
> > >       if (ret != 0) {
> > >           dev_err(dev, "failed to install irq (%d)\n", ret);
> > > -        goto err_src_clk;
> > > +        return ret;
> > 
> > Nit: this also could be "return dev_err_probe()"
> > 
> 
> The primary reason to call dev_err_probe() is that the error may be
> -EPROBE_DEFER, in which case the error message is suppressed.
> That is not the case for those two functions; they never return
> -EPROBE_DEFER. Calling dev_err_probe() would give the false impression
> that the functions _might_ return -EPROBE_DEFER.

That is subjective. In my book dev_err_probe() handling -EPROBE_DEFER is
only one aspect. Another is that using it allows to have return and error
message in a single line and also that if already other exit paths use
it to get a consistent style for the emitted messages. Having said that
*I* wouldn't assume that the previous call might return -EPROBE_DEFER
just because dev_err_probe() is used.

Having said that, I also don't think there is much harm if someone
thinks that a given function (here devm_request_irq()) might return
-EPROBE_DEFER.

Just my 0.02€
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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