linux-kernel - Re: [RESEND PATCH] driver core: Clear FWNODE_FLAG_LINKS_ADDED in device_links

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Message-ID: <dcb9094a-8e58-83ed-83af-05b879c23788@quicinc.com>
Date:   Wed, 27 Sep 2023 14:32:25 +0800
From:   Zhenhua Huang <quic_zhenhuah@...cinc.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <rafael@...nel.org>, <linux-kernel@...r.kernel.org>,
        <quic_pkondeti@...cinc.com>, <quic_tingweiz@...cinc.com>,
        <saravanak@...gle.com>
Subject: Re: [RESEND PATCH] driver core: Clear FWNODE_FLAG_LINKS_ADDED in
 device_links_purge()



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@...cinc.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
>>
> 
> 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