linux-kernel - Re: [PATCH 3/3] serial: sh-sci: Add reset support for RZ/G2L SoC

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Date:   Mon, 8 Nov 2021 17:39:52 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Prabhakar <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH 3/3] serial: sh-sci: Add reset support for RZ/G2L SoC

Hi Prabhakar,

On Wed, Nov 3, 2021 at 6:31 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> On RZ/G2L devices should be explicitly pulled out of reset for it
> to work. This patch adds support to read the "resets" property and
> performs deassert/assert when required.
>
> Also, propagate the error to the caller of sci_parse_dt() instead of
> returning NULL in case of failure.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Reviewed-by: Biju Das <biju.das.jz@...renesas.com>

Thanks for your patch!

> ---
> Hi Geert,
> For handling the resets I was in dual mind whether to perform
> reset based on compatible strings or soc-id, let me know your
> thoughts. Currently no SoC's use "renesas,sci" so using the same
> for performing the reset operation for SCI.

We do, on H8/300.

> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -3203,23 +3204,58 @@ static const struct of_device_id of_sci_match[] = {
>  };
>  MODULE_DEVICE_TABLE(of, of_sci_match);
>
> +static void sci_reset_control_assert(void *data)
> +{
> +       reset_control_assert(data);
> +}
> +
>  static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
>                                           unsigned int *dev_id)
>  {
>         struct device_node *np = pdev->dev.of_node;
> +       const struct of_device_id *of_id;
>         struct plat_sci_port *p;
>         struct sci_port *sp;
>         const void *data;
>         int id;
>
>         if (!IS_ENABLED(CONFIG_OF) || !np)
> -               return NULL;
> +               return ERR_PTR(-EINVAL);
> +
> +       of_id = of_match_device(of_sci_match, &pdev->dev);
> +       if (!of_id)
> +               return ERR_PTR(-EINVAL);
>
> -       data = of_device_get_match_data(&pdev->dev);
> +       if (!strcmp(of_id->compatible, "renesas,scif-r9a07g044") ||
> +           !strcmp(of_id->compatible, "renesas,sci")) {

This will match on H8/300, too, which doesn't have resets.
Please match against "renesas,sci-r9a07g044" instead.

Please don't use explicit strcmp() calls here, but add a flag to
of_sci_match[].data.

> +               struct reset_control *rstc;
> +               int ret;
> +
> +               rstc = devm_reset_control_get_exclusive(&pdev->dev, NULL);
> +               if (IS_ERR(rstc)) {
> +                       dev_err(&pdev->dev, "Error: missing reset ctrl\n");
> +                       return ERR_PTR(PTR_ERR(rstc));
> +               }
> +
> +               ret = reset_control_deassert(rstc);
> +               if (ret) {
> +                       dev_err(&pdev->dev, "failed to deassert %d\n", ret);
> +                       return ERR_PTR(ret);
> +               }
> +
> +               ret = devm_add_action_or_reset(&pdev->dev, sci_reset_control_assert, rstc);
> +               if (ret) {
> +                       dev_err(&pdev->dev, "failed to register assert devm action, %d\n",
> +                               ret);
> +                       return ERR_PTR(ret);
> +               }
> +       }
> +
> +       data = of_id->data;
>

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