Re: [RESEND PATCH] driver core: Clear FWNODE_FLAG_LINKS_ADDED in device_links_purge()

[Zhenhua Huang]

On 2023/9/27 13:57, Greg KH wrote:
> On Wed, Sep 27, 2023 at 10:30:10AM +0800, Zhenhua Huang wrote:
> > Flag FWNODE_FLAG_LINKS_ADDED stops fwnode links creation. Current kernel
> > only adds it once after fwnode links creation in fw_devlink_parse_fwnode().
> > After that even device links being purged, the flag will not be cleared.
> >
> > Fwnode links are converted to device links and will not be added back
> > forever in normal case. Essentially if a device is registered and
> > unregisted (also deleted) before it is probed (due to missing fwlink
> > dependencies, abort in device_links_check_suppliers), the fwlink is not
> > setup next when device is newly created again. This means the probe gets
> > called without meeting all dependencies.
> >
> > It usuallly happens in the case of a glue driver. Of_platform_populate()
> > allows us to populate subnodes. We may do it in ancestor node probing
> > function, then check subnode's probing status because there may be chances
> > that suppliers of subnode are not ready. We may further need to do
> > of_platform_depopulate(which purges device links) and in some time
> > of_platform_populate() again. Such case we miss fwnode links(so that device
> > links) during second time of populating subnodes.
> >
> > Fix it by Clearing FWNODE_FLAG_LINKS_ADDED flag in purging device link
> > func, indicates both fwnode links and device links are absent.
> >
> > Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx>
> > ---
> >   drivers/base/core.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index b7d7f41..2a1975d 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1630,6 +1630,10 @@ static void device_links_purge(struct device *dev)
> >   		__device_link_del(&link->kref);
> >   	}
> >   
> > +	/* Clear flags in fwnode. Give a chance to create fwnode link again */
> > +	if (dev->fwnode)
> > +		dev->fwnode->flags &= ~FWNODE_FLAG_LINKS_ADDED;
> > +
> >   	device_links_write_unlock();
> >   }
> >   
> > --
> > 2.7.4
>
> What commit id does this fix?

This commit c2c724c868c4("driver core: Add fw_devlink_parse_fwtree()"). 
Changelog mentioned:
"This function also ensures that no fwnode is parsed more than once by
    marking the fwnodes as parsed."

Thanks,
Zhenhua