Re: [PATCH net] net: bcmgenet: add hwtstamp callbacks to restore PHY timestamping

[Kory Maincent <kory.maincent@bootlin.com>]

On 9/18/26 10:20, Nicolai Buchwitz wrote:
> Hi James
> 
> On 18.9.2026 05:01, James Clark wrote:
>> Hardware timestamp configuration fails with EOPNOTSUPP on BCMGENET
>> interfaces connected to a timestamp-capable PHY. On a Raspberry Pi
>> CM4, "hwstamp_ctl -i eth0 -t 1 -r 12" fails with "SIOCSHWTSTAMP failed:
>> Operation not supported", preventing ptp4l from using hardware
>> timestamping.
>>
>> Commit 5062245a5a7f ("net: remove legacy way to get/set HW timestamp
>> config") removed the legacy ioctl fallback, assuming that all MAC
>> drivers supporting hardware timestamping implement ndo_hwtstamp_get()
>> and ndo_hwtstamp_set(), even when timestamping is provided only by
>> an attached PHY. BCMGENET does not implement these callbacks, so the
>> core rejects timestamp configuration requests before they reach
>> the PHY.
>>
>> Add ndo_hwtstamp_get() and ndo_hwtstamp_set() callbacks so the core
>> can dispatch timestamp configuration requests through its phylib
>> helpers. Both callbacks return -EOPNOTSUPP because the MAC itself
>> does not support hardware timestamping; requests for the PHY are
>> handled by the core without invoking these callbacks.
> 
> I've tested with and without your patch and can reproduce the issue / fix.
> IMHO the commit message should mention that 'get' isn't restored - it was
> already broken as the legacy path through phy_mii_ioctl() only handled
> SIOCSHWTSTAMP.
> 
>>
>> Fixes: 5062245a5a7f ("net: remove legacy way to get/set HW timestamp 
>> config")
>> Assisted-by: LLM
>> Signed-off-by: James Clark <jjc@jclark.com>
>> ---
>>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 15 +++++++++++++++
>>  1 file changed, 15 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/ 
>> net/ethernet/broadcom/genet/bcmgenet.c
>> index a2305e642..8ead37ff9 100644
>> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
>> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
>> @@ -3712,6 +3712,19 @@ static int bcmgenet_change_carrier(struct 
>> net_device *dev, bool new_carrier)
>>      return 0;
>>  }
>>
>> +static int bcmgenet_hwtstamp_get(struct net_device *dev,
>> +                 struct kernel_hwtstamp_config *cfg)
>> +{
>> +    return -EOPNOTSUPP;
>> +}
>> +
>> +static int bcmgenet_hwtstamp_set(struct net_device *dev,
>> +                 struct kernel_hwtstamp_config *cfg,
>> +                 struct netlink_ext_ack *extack)
>> +{
>> +    return -EOPNOTSUPP;
>> +}
> 
> The check that rejects the request is in dev_set_hwtstamp():
> 
>          if (!ops->ndo_hwtstamp_set)
>                  return -EOPNOTSUPP;
> 
> It runs before dev_set_hwtstamp_phylib() checks phy_is_default_hwtstamp()
> and nothing about this is specific to bcmgenet. Personally, I think this 
> should
> be better handled by the core than adding -EOPNOTSUPP stubs to the drivers.
> 
> I will send a patch for this.

I agree. Now that the legacy ioctl fallback has been removed from all 
NIC drivers we don't need this check to verify its support anymore.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com