linux-kernel - Re: [PATCH 2/4] phy: s32g: Add serdes subsystem phy

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Message-ID: <CAKfTPtAg201wXU_LuO-Y0M8k6ew8-vhKsjoHzJ1sxqp3Pn=wVQ@mail.gmail.com>
Date: Thu, 29 Jan 2026 14:02:09 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: vkoul@...nel.org, neil.armstrong@...aro.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, ciprianmarian.costea@....nxp.com, s32@....com, 
	p.zabel@...gutronix.de, ghennadi.procopciuc@....com, Ionut.Vicovan@....com, 
	linux-phy@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	netdev@...r.kernel.org, Frank.li@....com
Subject: Re: [PATCH 2/4] phy: s32g: Add serdes subsystem phy

On Thu, 29 Jan 2026 at 12:17, Russell King (Oracle)
<linux@...linux.org.uk> wrote:
>
> On Mon, Jan 26, 2026 at 10:21:57AM +0100, Vincent Guittot wrote:
> > +/*
> > + * Until now, there is no generic way to describe and set PCIe clock mode.
> > + * PCIe controller uses the default CRNS = 0 mode.
> > + */
> > +enum pcie_phy_mode {
> > +     CRNS = 0, /* Common Reference Clock, No Spread Spectrum */
> > +     CRSS = 1, /* Common Reference Clock, Spread Spectrum */
> > +     SRNS = 2, /* Separate Reference Clock, No Spread Spectrum */
> > +     SRIS = 3  /* Separate Reference Clock, Spread Spectrum */
> > +};
>
> So this is a PCIe thing. If it's part of the driver's API, then it
> should be common and not driver-private.
>
> > +static inline bool is_pcie_phy_mode_valid(int mode)
> > +{
> > +     switch (mode) {
> > +     case CRNS:
> > +     case CRSS:
> > +     case SRNS:
> > +     case SRIS:
> > +             return true;
> > +     default:
> > +             return false;
> > +     }
> > +}
>
> This checks that the submode is one of the PCIe private modes that this
> driver wants to see.
>
> > +
> > +static int s32g_serdes_phy_set_mode_ext(struct phy *p,
> > +                                     enum phy_mode mode, int submode)
> > +{
> > +     struct s32g_serdes *serdes = phy_get_drvdata(p);
> > +
> > +     if (mode == PHY_MODE_PCIE)
> > +             return -EINVAL;
> > +
> > +     if (!is_pcie_phy_mode_valid(submode))
> > +             return -EINVAL;
>
> This checks for the PCIe submode, but notice the test immediately
> above. PCIE mode is being rejected. So, this driver supports
> everything else but PCIe.
>
> That doesn't seem right.

It's a mistake

>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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