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

Zhenhua Huang
2023-09-27T06:34:59Z

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@quicinc.com>
>> ---
>> 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
>>
>
> Why is this a RESEND? What was wrong with the first version?

As per request of codes author, I CCed saravanak this time :)
Nothing else changed.

Thanks,
Zhenhua