linux-kernel - Re: [PATCHv4 net-next] net: ag71xx: get reset control using devm api

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Message-ID: <CAJq09z6JvN4t=xSsxAY97FAtkL2YfkVCGJ6G5YA_PTsC=jFtHg@mail.gmail.com>
Date: Thu, 29 Aug 2024 19:20:05 -0300
From: Luiz Angelo Daros de Luca <luizluca@...il.com>
To: Rosen Penev <rosenp@...il.com>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org, davem@...emloft.net, 
	edumazet@...gle.com, pabeni@...hat.com, linux@...linux.org.uk, 
	linux-kernel@...r.kernel.org, o.rempel@...gutronix.de, p.zabel@...gutronix.de
Subject: Re: [PATCHv4 net-next] net: ag71xx: get reset control using devm api

> On Tue, Aug 27, 2024 at 4:13 PM Jakub Kicinski <kuba@...nel.org> wrote:
> >
> > On Mon, 26 Aug 2024 14:21:57 -0700 Rosen Penev wrote:
> > > Currently, the of variant is missing reset_control_put in error paths.
> > > The devm variant does not require it.
> > >
> > > Allows removing mdio_reset from the struct as it is not used outside the
> > > function.
> >
> > > @@ -683,6 +682,7 @@ static int ag71xx_mdio_probe(struct ag71xx *ag)
> > >       struct device *dev = &ag->pdev->dev;
> > >       struct net_device *ndev = ag->ndev;
> > >       static struct mii_bus *mii_bus;
> > > +     struct reset_control *mdio_reset;
> >
> > nit: maintain the longest to shortest ordering of the variables
> > (sorted by line length not type length)
> >
> > >       struct device_node *np, *mnp;
> > >       int err;
> > >
> > > @@ -698,10 +698,10 @@ static int ag71xx_mdio_probe(struct ag71xx *ag)
> > >       if (!mii_bus)
> > >               return -ENOMEM;
> > >
> > > -     ag->mdio_reset = of_reset_control_get_exclusive(np, "mdio");
> > > -     if (IS_ERR(ag->mdio_reset)) {
> > > +     mdio_reset = devm_reset_control_get_exclusive(dev, "mdio");



> > > +     if (IS_ERR(mdio_reset)) {
> > >               netif_err(ag, probe, ndev, "Failed to get reset mdio.\n");
> > > -             return PTR_ERR(ag->mdio_reset);
> > > +             return PTR_ERR(mdio_reset);
> > >       }
> > >
> > >       mii_bus->name = "ag71xx_mdio";
> > > @@ -712,10 +712,10 @@ static int ag71xx_mdio_probe(struct ag71xx *ag)
> > >       mii_bus->parent = dev;
> > >       snprintf(mii_bus->id, MII_BUS_ID_SIZE, "%s.%d", np->name, ag->mac_idx);
> > >
> > > -     if (!IS_ERR(ag->mdio_reset)) {
> > > -             reset_control_assert(ag->mdio_reset);
> > > +     if (!IS_ERR(mdio_reset)) {
> >
> > Are you planning to follow up to remove this check?
> > Would be nice to do that as second patch in the same series
> I actually have no idea why this is here. I assume it's some mistake.
> I don't think it's meant to be optional...

{devm,of}_reset_control_get_exclusive() will return an error if the OF
node is missing. If it should be optional, it should be
devm_reset_control_get_optional_exclusive(), which would return NULL
if it is missing.

The equivalent driver used in OpenWrt does explicitly make it
optional. https://github.com/openwrt/openwrt/blob/4646aa169986036772b9f75393c08508d20ddf8b/target/linux/ath79/files/drivers/net/ethernet/atheros/ag71xx/ag71xx_main.c#L1532,
while the mac_reset is mandatory. They might have a reason for that or
maybe only heritage from Atheros AG7100 driver.

> >
> > > +             reset_control_assert(mdio_reset);
> > >               msleep(100);
> > > -             reset_control_deassert(ag->mdio_reset);
> > > +             reset_control_deassert(mdio_reset);
> > >               msleep(200);
> > >       }

Regards,

Luiz