netdev - Re: [PATCH net-next] mdio: mdiobus: setup of

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Date:   Tue, 15 Jun 2021 22:09:07 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Ioana Ciornei <ciorneiioana@...il.com>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        calvin.johnson@....nxp.com, hkallweit1@...il.com,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: Re: [PATCH net-next] mdio: mdiobus: setup of_node for the MDIO device

On Tue, Jun 15, 2021 at 08:31:06PM +0200, Andrew Lunn wrote:
> On Tue, Jun 15, 2021 at 06:13:31PM +0100, Russell King (Oracle) wrote:
> > On Tue, Jun 15, 2021 at 06:44:01PM +0300, Ioana Ciornei wrote:
> > > From: Ioana Ciornei <ioana.ciornei@....com>
> > > 
> > > By mistake, the of_node of the MDIO device was not setup in the patch
> > > linked below. As a consequence, any PHY driver that depends on the
> > > of_node in its probe callback was not be able to successfully finish its
> > > probe on a PHY, thus the Generic PHY driver was used instead.
> > > 
> > > Fix this by actually setting up the of_node.
> > > 
> > > Fixes: bc1bee3b87ee ("net: mdiobus: Introduce fwnode_mdiobus_register_phy()")
> > > Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
> > > ---
> > >  drivers/net/mdio/fwnode_mdio.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/net/mdio/fwnode_mdio.c b/drivers/net/mdio/fwnode_mdio.c
> > > index e96766da8de4..283ddb1185bd 100644
> > > --- a/drivers/net/mdio/fwnode_mdio.c
> > > +++ b/drivers/net/mdio/fwnode_mdio.c
> > > @@ -65,6 +65,7 @@ int fwnode_mdiobus_phy_device_register(struct mii_bus *mdio,
> > >  	 * can be looked up later
> > >  	 */
> > >  	fwnode_handle_get(child);
> > > +	phy->mdio.dev.of_node = to_of_node(child);
> > >  	phy->mdio.dev.fwnode = child;
> > 
> > Yes, this is something that was missed, but let's first look at what
> > other places to when setting up a device:
> > 
> >         pdev->dev.fwnode = pdevinfo->fwnode;
> >         pdev->dev.of_node = of_node_get(to_of_node(pdev->dev.fwnode));
> >         pdev->dev.of_node_reused = pdevinfo->of_node_reused;
> > 
> >         dev->dev.of_node = of_node_get(np);
> >         dev->dev.fwnode = &np->fwnode;
> > 
> >         dev->dev.of_node = of_node_get(node);
> >         dev->dev.fwnode = &node->fwnode;
> > 
> > That seems to be pretty clear that an of_node_get() is also needed.
> 
> I think it also shows we have very little consistency, and the recent
> patchset needs a bit of cleanup. Maybe yet another helper which when
> passed a struct device * and a node pointer, it sets both values?

I do like that idea - maybe a couple of helpers, one that takes the
of_node for a struct device, and another that takes a fwnode and
does the appropriate stuff.

Note that platform_device_release() does this:

	of_node_put(pa->pdev.dev.of_node);

which is currently fine, because platform devices appear to only
have their DT refcount increased. From what I can tell from looking
at drivers/acpi/arm64/iort.c, ACPI fwnodes don't look like they're
refcounted. Seems we're wading into something of a mess here. :(

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