linux-kernel - Re: [PATCH 06/37] clk: renesas: rzg2l: wait for status bit of SD mux before continuing

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Date:   Thu, 14 Sep 2023 13:42:04 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Claudiu <claudiu.beznea@...on.dev>
Cc:     mturquette@...libre.com, sboyd@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        ulf.hansson@...aro.org, linus.walleij@...aro.org,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        magnus.damm@...il.com, catalin.marinas@....com, will@...nel.org,
        prabhakar.mahadev-lad.rj@...renesas.com,
        biju.das.jz@...renesas.com, quic_bjorande@...cinc.com,
        arnd@...db.de, konrad.dybcio@...aro.org, neil.armstrong@...aro.org,
        nfraprado@...labora.com, rafal@...ecki.pl,
        wsa+renesas@...g-engineering.com,
        linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 06/37] clk: renesas: rzg2l: wait for status bit of SD mux
 before continuing

Hi Claudiu,

On Tue, Sep 12, 2023 at 6:52 AM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> Hardware user manual of RZ/G2L (r01uh0914ej0130-rzg2l-rzg2lc.pdf,
> chapter 7.4.7 Procedure for Switching Clocks by the Dynamic Switching
> Frequency Selectors) specifies that we need to check CPG_PL2SDHI_DSEL for
> SD clock switching status.
>
> Fixes: eaff33646f4cb ("clk: renesas: rzg2l: Add SDHI clk mux support")
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Thanks for your patch!

> --- a/drivers/clk/renesas/rzg2l-cpg.c
> +++ b/drivers/clk/renesas/rzg2l-cpg.c
> @@ -188,7 +188,8 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
>         u32 off = GET_REG_OFFSET(hwdata->conf);
>         u32 shift = GET_SHIFT(hwdata->conf);
>         const u32 clk_src_266 = 2;
> -       u32 bitmask;
> +       u32 msk, val, bitmask;
> +       int ret;
>
>         /*
>          * As per the HW manual, we should not directly switch from 533 MHz to
> @@ -203,9 +204,6 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
>          */
>         bitmask = (GENMASK(GET_WIDTH(hwdata->conf) - 1, 0) << shift) << 16;
>         if (index != clk_src_266) {
> -               u32 msk, val;
> -               int ret;
> -
>                 writel(bitmask | ((clk_src_266 + 1) << shift), priv->base + off);
>
>                 msk = off ? CPG_CLKSTATUS_SELSDHI1_STS : CPG_CLKSTATUS_SELSDHI0_STS;
> @@ -221,7 +219,13 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
>
>         writel(bitmask | ((index + 1) << shift), priv->base + off);
>
> -       return 0;
> +       ret = readl_poll_timeout(priv->base + CPG_CLKSTATUS, val,
> +                                !(val & msk), 100,

"msk" may be uninitialized.

> +                                CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US);
> +       if (ret)
> +               dev_err(priv->dev, "failed to switch clk source\n");
> +
> +       return ret;

This is now (supposed to be) doing the same thing twice, once using
clk_src_266, and then again with the wanted index, so why not introduce
a small helper? That would have avoided the uninitialized variable, too.

I know you're rewriting this code in "[PATCH 18/37] clk: renesas:
rzg2l: refactor sd mux driver", but even after that, you always do
a register write before calling rzg2l_cpg_wait_clk_update_done(),
so it may still be a net win.

>  }
>
>  static u8 rzg2l_cpg_sd_clk_mux_get_parent(struct clk_hw *hw)

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