linux-kernel - Re: [PATCH v3 6/7] soc: renesas: rmobile-sysc: Convert to readl_poll_timeout

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Date:   Mon, 5 Jun 2023 15:15:16 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Magnus Damm <magnus.damm@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Dejin Zheng <zhengdejin5@...il.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Lindgren <tony@...mide.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Tero Kristo <tero.kristo@...ux.intel.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/7] soc: renesas: rmobile-sysc: Convert to readl_poll_timeout_atomic()

On Fri, Jun 2, 2023 at 10:51 AM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> Use readl_poll_timeout_atomic() instead of open-coding the same
> operation.
>
>   1. rmobile_pd_power_down(): as typically less than 20 retries are
>      needed, PSTR_RETRIES (100) µs is a suitable timeout value.
>
>   2. __rmobile_pd_power_up(): the old method of first polling some
>      cycles with a 1 µs delay, followed by more polling cycles without
>      any delay didn't make much sense, as the latter was insignificant
>      compared to the former.  Furthermore, typically no retries are
>      needed.  Hence just retain the polling with delay.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

> diff --git a/drivers/soc/renesas/rmobile-sysc.c b/drivers/soc/renesas/rmobile-sysc.c
> index 728ebac98e14a5cc..5d621c35fba1116a 100644

> @@ -74,25 +71,17 @@ static int rmobile_pd_power_down(struct generic_pm_domain *genpd)
>
>  static int __rmobile_pd_power_up(struct rmobile_pm_domain *rmobile_pd)
>  {
> -       unsigned int mask = BIT(rmobile_pd->bit_shift);
> -       unsigned int retry_count;
> -       int ret = 0;
> +       unsigned int val, mask = BIT(rmobile_pd->bit_shift);
> +       int ret;

Oops, "ret" should still be initialized to zero.

>
>         if (readl(rmobile_pd->base + PSTR) & mask)
>                 return ret;
>
>         writel(mask, rmobile_pd->base + SWUCR);
>
> -       for (retry_count = 2 * PSTR_RETRIES; retry_count; retry_count--) {
> -               if (!(readl(rmobile_pd->base + SWUCR) & mask))
> -                       break;
> -               if (retry_count > PSTR_RETRIES)
> -                       udelay(PSTR_DELAY_US);
> -               else
> -                       cpu_relax();
> -       }
> -       if (!retry_count)
> -               ret = -EIO;
> +       ret = readl_poll_timeout_atomic(rmobile_pd->base + SWUCR, val,
> +                                       (val & mask), PSTR_DELAY_US,
> +                                       PSTR_RETRIES * PSTR_DELAY_US);
>
>         pr_debug("%s: Power on, 0x%08x -> PSTR = 0x%08x\n",
>                  rmobile_pd->genpd.name, mask,

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