Re: [RFC PATCH net 5/5] net: dsa: xrs700x: be compatible with masters which unregister on shutdown

George McCollister
2021-09-13T13:40:01Z

On Sun, Sep 12, 2021 at 7:09 AM Vladimir Oltean <vladimir.oltean@nxp.com> wrote:
>
> Since commit 2f1e8ea726e9 ("net: dsa: link interfaces with the DSA
> master to get rid of lockdep warnings"), DSA gained a requirement which
> it did not fulfill, which is to unlink itself from the DSA master at
> shutdown time.
>
> Since the Arrow SpeedChips XRS700x driver was introduced after the bad
> commit, it has never worked with DSA masters which decide to unregister
> their net_device on shutdown, effectively hanging the reboot process.
> To fix that, we need to call dsa_switch_shutdown.
>
> These devices can be connected by I2C or by MDIO, and if I search for
> I2C or MDIO bus drivers that implement their ->shutdown by redirecting
> it to ->remove I don't see any, however this does not mean it would not
> be possible. To be compatible with that pattern, it is necessary to
> implement an "if this then not that" scheme, to avoid ->remove and
> ->shutdown from being called both for the same struct device.
>
> Fixes: ee00b24f32eb ("net: dsa: add Arrow SpeedChips XRS700x driver")
> Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
> Reported-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> ---
> drivers/net/dsa/xrs700x/xrs700x.c | 6 ++++++
> drivers/net/dsa/xrs700x/xrs700x.h | 1 +
> drivers/net/dsa/xrs700x/xrs700x_i2c.c | 18 ++++++++++++++++++
> drivers/net/dsa/xrs700x/xrs700x_mdio.c | 18 ++++++++++++++++++
> 4 files changed, 43 insertions(+)
>
> diff --git a/drivers/net/dsa/xrs700x/xrs700x.c b/drivers/net/dsa/xrs700x/xrs700x.c
> index 130abb0f1438..469420941054 100644
> --- a/drivers/net/dsa/xrs700x/xrs700x.c
> +++ b/drivers/net/dsa/xrs700x/xrs700x.c
> @@ -822,6 +822,12 @@ void xrs700x_switch_remove(struct xrs700x *priv)
> }
> EXPORT_SYMBOL(xrs700x_switch_remove);
>
> +void xrs700x_switch_shutdown(struct xrs700x *priv)
> +{
> + dsa_switch_shutdown(priv->ds);
> +}
> +EXPORT_SYMBOL(xrs700x_switch_shutdown);
> +
> MODULE_AUTHOR("George McCollister <george.mccollister@gmail.com>");
> MODULE_DESCRIPTION("Arrow SpeedChips XRS700x DSA driver");
> MODULE_LICENSE("GPL v2");
> diff --git a/drivers/net/dsa/xrs700x/xrs700x.h b/drivers/net/dsa/xrs700x/xrs700x.h
> index ff62cf61b091..4d58257471d2 100644
> --- a/drivers/net/dsa/xrs700x/xrs700x.h
> +++ b/drivers/net/dsa/xrs700x/xrs700x.h
> @@ -40,3 +40,4 @@ struct xrs700x {
> struct xrs700x *xrs700x_switch_alloc(struct device *base, void *devpriv);
> int xrs700x_switch_register(struct xrs700x *priv);
> void xrs700x_switch_remove(struct xrs700x *priv);
> +void xrs700x_switch_shutdown(struct xrs700x *priv);
> diff --git a/drivers/net/dsa/xrs700x/xrs700x_i2c.c b/drivers/net/dsa/xrs700x/xrs700x_i2c.c
> index 489d9385b4f0..6deae388a0d6 100644
> --- a/drivers/net/dsa/xrs700x/xrs700x_i2c.c
> +++ b/drivers/net/dsa/xrs700x/xrs700x_i2c.c
> @@ -109,11 +109,28 @@ static int xrs700x_i2c_remove(struct i2c_client *i2c)
> {
> struct xrs700x *priv = i2c_get_clientdata(i2c);
>
> + if (!priv)
> + return 0;
> +
> xrs700x_switch_remove(priv);
>
> + i2c_set_clientdata(i2c, NULL);
> +
> return 0;
> }
>
> +static void xrs700x_i2c_shutdown(struct i2c_client *i2c)
> +{
> + struct xrs700x *priv = i2c_get_clientdata(i2c);
> +
> + if (!priv)
> + return;
> +
> + xrs700x_switch_shutdown(priv);
> +
> + i2c_set_clientdata(i2c, NULL);
> +}
> +
> static const struct i2c_device_id xrs700x_i2c_id[] = {
> { "xrs700x-switch", 0 },
> {},
> @@ -137,6 +154,7 @@ static struct i2c_driver xrs700x_i2c_driver = {
> },
> .probe = xrs700x_i2c_probe,
> .remove = xrs700x_i2c_remove,
> + .shutdown = xrs700x_i2c_shutdown,
> .id_table = xrs700x_i2c_id,
> };
>
> diff --git a/drivers/net/dsa/xrs700x/xrs700x_mdio.c b/drivers/net/dsa/xrs700x/xrs700x_mdio.c
> index 44f58bee04a4..d01cf1073d49 100644
> --- a/drivers/net/dsa/xrs700x/xrs700x_mdio.c
> +++ b/drivers/net/dsa/xrs700x/xrs700x_mdio.c
> @@ -136,7 +136,24 @@ static void xrs700x_mdio_remove(struct mdio_device *mdiodev)
> {
> struct xrs700x *priv = dev_get_drvdata(&mdiodev->dev);
>
> + if (!priv)
> + return;
> +
> xrs700x_switch_remove(priv);
> +
> + dev_set_drvdata(&mdiodev->dev, NULL);
> +}
> +
> +static void xrs700x_mdio_shutdown(struct mdio_device *mdiodev)
> +{
> + struct xrs700x *priv = dev_get_drvdata(&mdiodev->dev);
> +
> + if (!priv)
> + return;
> +
> + xrs700x_switch_shutdown(priv);
> +
> + dev_set_drvdata(&mdiodev->dev, NULL);
> }
>
> static const struct of_device_id __maybe_unused xrs700x_mdio_dt_ids[] = {
> @@ -155,6 +172,7 @@ static struct mdio_driver xrs700x_mdio_driver = {
> },
> .probe = xrs700x_mdio_probe,
> .remove = xrs700x_mdio_remove,
> + .shutdown = xrs700x_mdio_shutdown,
> };
>
> mdio_module_driver(xrs700x_mdio_driver);
> --
> 2.25.1
>

Looks good to me.
Assuming we do Reviewed-by for RFCs:
Reviewed-by: George McCollister <george.mccollister@gmail.com>