Re: [PATCH 12/37] clk: renesas: rzg2l: reduce the critical area

[Geert Uytterhoeven]

Hi Claudiu,

On Tue, Sep 12, 2023 at 6:52 AM Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
> spinlock in rzg2l_mod_clock_endisable() is intended to protect the accesses
> to hardware register. There is no need to protect the instructions that set
> temporary variable which will be then written to register. Thus limit the
> spinlock only to the hardware register access.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

Thanks for your patch!

> --- a/drivers/clk/renesas/rzg2l-cpg.c
> +++ b/drivers/clk/renesas/rzg2l-cpg.c
> @@ -912,13 +912,13 @@ static int rzg2l_mod_clock_endisable(struct clk_hw *hw, bool enable)
>
>         dev_dbg(dev, "CLK_ON %u/%pC %s\n", CLK_ON_R(reg), hw->clk,
>                 enable ? "ON" : "OFF");
> -       spin_lock_irqsave(&priv->rmw_lock, flags);
>
>         value = bitmask << 16;
>         if (enable)
>                 value |= bitmask;
> -       writel(value, priv->base + CLK_ON_R(reg));
>
> +       spin_lock_irqsave(&priv->rmw_lock, flags);
> +       writel(value, priv->base + CLK_ON_R(reg));
>         spin_unlock_irqrestore(&priv->rmw_lock, flags);

After this, it becomes obvious there is nothing to protect at all,
so the locking can just be removed from this function?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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