linux-kernel - Re: [PATCH v4 11/22] phy: renesas: rcar-gen3-usb2: Use mux-state for phyrst management

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Message-ID: <CAMuHMdVYvV8WXBKmQEMnw_qgMdoUDLreNJM3UqEtoZ29AR6NoA@mail.gmail.com>
Date: Wed, 26 Nov 2025 08:43:00 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>
Cc: tomm.merciai@...il.com, linux-renesas-soc@...r.kernel.org, 
	biju.das.jz@...renesas.com, Peter Rosin <peda@...ntia.se>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Philipp Zabel <p.zabel@...gutronix.de>, 
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, Magnus Damm <magnus.damm@...il.com>, 
	Sebastian Reichel <sebastian.reichel@...labora.com>, Andi Shyti <andi.shyti@...nel.org>, 
	Jonathan Cameron <jonathan.cameron@...wei.com>, Uwe Kleine-König <ukleinek@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org
Subject: Re: [PATCH v4 11/22] phy: renesas: rcar-gen3-usb2: Use mux-state for
 phyrst management

Hi Tommaso,

On Tue, 25 Nov 2025 at 16:57, Tommaso Merciai
<tommaso.merciai.xr@...renesas.com> wrote:
> On Tue, Nov 25, 2025 at 03:10:22PM +0100, Geert Uytterhoeven wrote:
> > On Fri, 21 Nov 2025 at 16:14, Tommaso Merciai
> > <tommaso.merciai.xr@...renesas.com> wrote:
> > > Add support for selecting the phyrst mux-state using the Linux mux
> > > subsystem in the R-Car Gen3 USB2 PHY driver. This ensures correct hardware
> > > initialization and integration with systems utilizing the mux-state device
> > > tree property.
> > >
> > > A temporary wrapper for optional muxes is introduced until native support
> > > is available in the multiplexer subsystem.
> > >
> > > Signed-off-by: Tommaso Merciai <tommaso.merciai.xr@...renesas.com>

> > > --- a/drivers/phy/renesas/phy-rcar-gen3-usb2.c
> > > +++ b/drivers/phy/renesas/phy-rcar-gen3-usb2.c
> > > @@ -938,11 +939,27 @@ static int rcar_gen3_phy_usb2_vbus_regulator_register(struct rcar_gen3_chan *cha
> > >         return rcar_gen3_phy_usb2_vbus_regulator_get_exclusive_enable(channel, enable);
> > >  }
> > >
> > > +/* Temporary wrapper until the multiplexer subsystem supports optional muxes */
> > > +static inline struct mux_state *
> > > +devm_mux_state_get_optional(struct device *dev, const char *mux_name)
> > > +{
> > > +       if (!of_property_present(dev->of_node, "mux-states"))
> > > +               return NULL;
> > > +
> > > +       return devm_mux_state_get(dev, mux_name);
> > > +}
> > > +
> > > +static void rcar_gen3_phy_mux_state_deselect(void *data)
> > > +{
> > > +       mux_state_deselect(data);
> > > +}
> > > +
> > >  static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
> > >  {
> > >         struct device *dev = &pdev->dev;
> > >         struct rcar_gen3_chan *channel;
> > >         struct phy_provider *provider;
> > > +       struct mux_state *mux_state;
> > >         int ret = 0, i, irq;
> > >
> > >         if (!dev->of_node) {
> > > @@ -1019,6 +1036,23 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
> > >                 phy_set_drvdata(channel->rphys[i].phy, &channel->rphys[i]);
> > >         }
> > >
> > > +       mux_state = devm_mux_state_get_optional(dev, NULL);
> > > +       if (IS_ERR(mux_state)) {
> > > +               if (PTR_ERR(mux_state) == -EPROBE_DEFER)
> > > +                       return PTR_ERR(mux_state);
> > > +               mux_state = NULL;
> >
> > No need to set mux_state to NULL, as mux_state is not used below.
> >
> > However, shouldn't you propagate all errors up?
> > If the mux is not present, mux_state should already be NULL,
> > i.e. IS_ERR(mux_state) would be false.
> >
> > > +       } else {
> > > +               ret = mux_state_select(mux_state);
> >
> > This causes a crash on R-Car Gen3 and RZ/Five, as mux_state_select()
> > doesn't handle NULL pointers gracefully yet.
> >
> > Adding a check like
> >
> >     -       } else {
> >     +       } else if (mux_state) {
> >
> > fixes the issue.
>
> Thank you for checking this!
>
> Ack :)
> I will switch to:
>
>         mux_state = devm_mux_state_get_optional(dev, NULL);
>         if (IS_ERR(mux_state)) {
>                 return PTR_ERR(mux_state);
>         } else if (mux_state) {

Please no else after return.

>                 ret = mux_state_select(mux_state);
>                 if (ret)
>                         return dev_err_probe(dev, ret, "Failed to select USB mux\n");
>
>                 ret = devm_add_action_or_reset(dev, rcar_gen3_phy_mux_state_deselect,
>                                                mux_state);
>                 if (ret)
>                         return dev_err_probe(dev, ret,
>                                              "Failed to register USB mux state deselect\n");
>         }
>
> In v5.

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