linux-kernel - Re: [PATCH v2 3/3] serial: sh-sci: Add support to deassert/assert reset line

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Date:   Tue, 9 Nov 2021 13:07:19 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        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>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2 3/3] serial: sh-sci: Add support to deassert/assert
 reset line

Hi Geert,

Thank you for the review.

On Tue, Nov 9, 2021 at 12:58 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Tue, Nov 9, 2021 at 1:17 PM Lad Prabhakar
> <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > On RZ/G2L SoC we need to explicitly deassert the reset line
> > for the device to work, use this opportunity to deassert/assert
> > reset line in sh-sci driver.
> >
> > This patch adds support to read the "resets" property (if available)
> > from DT and perform 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>
> > ---
> > v1->v2
> > * deassert/assert reset line if available on all SoC's
> > * Updated commit message
>
> Thanks for the update!
>
> > --- a/drivers/tty/serial/sh-sci.c
> > +++ b/drivers/tty/serial/sh-sci.c
> > @@ -37,6 +37,7 @@
> >  #include <linux/of_device.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/reset.h>
> >  #include <linux/scatterlist.h>
> >  #include <linux/serial.h>
> >  #include <linux/serial_sci.h>
> > @@ -3203,23 +3204,53 @@ 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;
>
> Not needed.
>
Agreed.

> > +       struct reset_control *rstc;
> >         struct plat_sci_port *p;
> >         struct sci_port *sp;
> >         const void *data;
> > -       int id;
> > +       int id, ret;
> >
> >         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);
>
> Please keep the old construct using of_device_get_match_data().
>
OK.

> > +       rstc = devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
> > +       if (IS_ERR(rstc)) {
> > +               dev_err(&pdev->dev, "failed to get reset ctrl %ld\n", PTR_ERR(rstc));
> > +               return ERR_PTR(PTR_ERR(rstc));
>
> The error might be -EPROBE_DEFER, so please use
> "return ERR_PTR(dev_err_probe(...))", to avoid printing the message
> in case of probe deferral.
>
Agreed, will use dev_err_probe().

> BTW, ERR_CAST() is a shorthand for ERR_PTR(PTR_ERR()).
>
Thanks for the pointer.

> > +       }
> > +
> > +       ret = reset_control_deassert(rstc);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "failed to deassert reset %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;
> >
> >         p = devm_kzalloc(&pdev->dev, sizeof(struct plat_sci_port), GFP_KERNEL);
> >         if (!p)
> > -               return NULL;
> > +               return ERR_PTR(-ENOMEM);
> >
> >         /* Get the line number from the aliases node. */
> >         id = of_alias_get_id(np, "serial");
>
> I gave this a try on Salvator-XS, and noticed no regressions.
> I will test this on more SCIF variants later.
>
Thanks, I will re-spin a v3 just for this lone patch. I hope that's OK.

Cheers,
Prabhakar

> 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