[V4,2/2] net: ethernet: ravb: Enable optional refclk

For devices that use a programmable clock for the AVB reference clock,
the driver may need to enable them.  Add code to find the optional clock
and enable it when available.

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>

---
V4:  Eliminate the NULL check when disabling refclk, and add a line
     to disable the refclk if there is a failure after it's been
     initialized.

V3:  Change 'avb' to 'AVB'
     Remove unnessary else statement and pointer maniupluation when
     enabling the refclock.
     Add disable_unprepare call in remove funtion.

V2:  The previous patch to fetch the fclk was dropped.  In its place
     is code to enable the refclk

On Tue, Apr 13, 2021 at 2:33 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Adam,
>
> On Mon, Apr 12, 2021 at 3:27 PM Adam Ford <aford173@gmail.com> wrote:
> > For devices that use a programmable clock for the AVB reference clock,
> > the driver may need to enable them.  Add code to find the optional clock
> > and enable it when available.
> >
> > Signed-off-by: Adam Ford <aford173@gmail.com>
> > Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> >
> > ---
> > V4:  Eliminate the NULL check when disabling refclk, and add a line
> >      to disable the refclk if there is a failure after it's been
> >      initialized.
>
> Thanks for the update!
>
> > --- a/drivers/net/ethernet/renesas/ravb_main.c
> > +++ b/drivers/net/ethernet/renesas/ravb_main.c
> > @@ -2148,6 +2148,13 @@ static int ravb_probe(struct platform_device *pdev)
> >                 goto out_release;
> >         }
> >
> > +       priv->refclk = devm_clk_get_optional(&pdev->dev, "refclk");
> > +       if (IS_ERR(priv->refclk)) {
> > +               error = PTR_ERR(priv->refclk);
> > +               goto out_release;
>
> Note that this will call clk_disable_unprepare() in case of failure, which is
> fine, as that function is a no-op in case of a failed clock.

Geert,

A bot reported that if I jump to out_release may try to free a clock
if some instances where priv isn't defined.
Currently, the priv->clk isn't freed either.  I have heard some
back-and-forth discussions in other threads on whether or not devm
functions auto free or not.

I'm fine with sending a V5 to make the free for the refclock happen
only when the priv has successfully initialized.  Should I also add
one for freeing priv->clk and change all the other goto out_release
commands to point to this new section?

I am thinking it would like something like:

free_refclk:
    clk_disable_unprepare(priv->refclk);
free_clk;
    clk_disable_unprepare(priv->clk);
out_release:
    free_netdev(ndev);
    ....


adam
>
> > +       }
> > +       clk_prepare_enable(priv->refclk);
> > +
> >         ndev->max_mtu = 2048 - (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN);
> >         ndev->min_mtu = ETH_MIN_MTU;
> >
> > @@ -2244,6 +2251,7 @@ static int ravb_probe(struct platform_device *pdev)
> >         if (chip_id != RCAR_GEN2)
> >                 ravb_ptp_stop(ndev);
> >  out_release:
> > +       clk_disable_unprepare(priv->refclk);
> >         free_netdev(ndev);
> >
> >         pm_runtime_put(&pdev->dev);
>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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

Hi Adam,

On Wed, Apr 14, 2021 at 3:08 PM Adam Ford <aford173@gmail.com> wrote:
> On Tue, Apr 13, 2021 at 2:33 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > On Mon, Apr 12, 2021 at 3:27 PM Adam Ford <aford173@gmail.com> wrote:
> > > For devices that use a programmable clock for the AVB reference clock,
> > > the driver may need to enable them.  Add code to find the optional clock
> > > and enable it when available.
> > >
> > > Signed-off-by: Adam Ford <aford173@gmail.com>
> > > Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> > >
> > > ---
> > > V4:  Eliminate the NULL check when disabling refclk, and add a line
> > >      to disable the refclk if there is a failure after it's been
> > >      initialized.
> >
> > Thanks for the update!
> >
> > > --- a/drivers/net/ethernet/renesas/ravb_main.c
> > > +++ b/drivers/net/ethernet/renesas/ravb_main.c
> > > @@ -2148,6 +2148,13 @@ static int ravb_probe(struct platform_device *pdev)
> > >                 goto out_release;
> > >         }
> > >
> > > +       priv->refclk = devm_clk_get_optional(&pdev->dev, "refclk");
> > > +       if (IS_ERR(priv->refclk)) {
> > > +               error = PTR_ERR(priv->refclk);
> > > +               goto out_release;
> >
> > Note that this will call clk_disable_unprepare() in case of failure, which is
> > fine, as that function is a no-op in case of a failed clock.
>
> Geert,
>
> A bot reported that if I jump to out_release may try to free a clock
> if some instances where priv isn't defined.

As priv is allocated using alloc_etherdev_mqs(), priv->refclk is
NULL initially, but priv itself may indeed not be initialized when the first
"goto out_release" is taken.  Sorry for missing that.

> Currently, the priv->clk isn't freed either.  I have heard some
> back-and-forth discussions in other threads on whether or not devm
> functions auto free or not.

The devm_clk_get_optional() will be undone automatically, so there
is no need to handle that explicitly.

> I'm fine with sending a V5 to make the free for the refclock happen
> only when the priv has successfully initialized.  Should I also add

As this patch has been applied to net-next, you''ll have to send
a follow-up fix patch, not a v5.

> one for freeing priv->clk and change all the other goto out_release
> commands to point to this new section?

No, not for priv->clk, due to devm_*().

> I am thinking it would like something like:
>
> free_refclk:
>     clk_disable_unprepare(priv->refclk);

OK.

> free_clk;
>     clk_disable_unprepare(priv->clk);

NAK, as priv->clk is not enabled in ravb_probe().

> out_release:
>     free_netdev(ndev);
>     ....

OK.

Thanks!

Gr{oetje,eeting}s,

                        Geert