Re: [PATCH net-next v3 1/2] net: macb: Poll for link state changes when using the internal PCS.

On 8/5/26 15:43, Théo Lebrun wrote:
> Hello Nathan,
>
> On Wed Jul 29, 2026 at 9:21 PM CEST, Nathan Whitehorn wrote:
>> When used with an offboard transceiver (e.g. an SFP), link state needs
>> to be measured at the PCS rather than an onboard PHY. Poll the link
>> state when the PCS is active to allow the kernel to detect link state
>> changes in this case.
>>
>> Signed-off-by: Nathan Whitehorn <[email protected]>
>> ---
>>   drivers/net/ethernet/cadence/macb_main.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
>> index d394f1f43b68..c15a9c7e69d3 100644
>> --- a/drivers/net/ethernet/cadence/macb_main.c
>> +++ b/drivers/net/ethernet/cadence/macb_main.c
>> @@ -1025,6 +1025,7 @@ static int macb_mii_probe(struct net_device *dev)
>>   	struct macb *bp = netdev_priv(dev);
>>   
>>   	bp->phylink_sgmii_pcs.ops = &macb_phylink_pcs_ops;
>> +	bp->phylink_sgmii_pcs.poll = true;
>>   	bp->phylink_usx_pcs.ops = &macb_phylink_usx_pcs_ops;
>>   
>>   	bp->phylink_config.dev = &dev->dev;
> Hardware has an IRQ for that, would you want to use it instead of
> polling? The user guide contains more info.
>
>     /* Bitfields in ISR/IER/IDR/IMR */
>     ...
>     #define MACB_ISR_LINK_OFFSET  9 /* Enable link change interrupt */
>     #define MACB_ISR_LINK_SIZE 1
>     ...
>
> I've checked with an on-board SGMII PHY and I get an IRQ once unmasked.
>
> If you don't care, then:
>
> Reviewed-by: Théo Lebrun <[email protected]>

Thanks, that's really good to know! I will look into it. For right now, 
though, if it is all right, I think I would prefer to keep this as-is 
and come back with a later patch that switches this to use the 
interrupt, just to get the base functionality into the tree.
-Nathan

>
> Regards,
>
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>

-- 
Nathan Whitehorn (he/him)
Associate Professor
Department of Physics and Astronomy
Michigan State University
Biomedical and Physical Sciences 3225
East Lansing, MI 48824
(517) 884-5563