ClearFog GT 8K not initialising SFP-H10GB-CU1M transceiver on 5.4.150

[Greg KH]

On Mon, Nov 22, 2021 at 07:53:44PM +0000, Russell King (Oracle) wrote:
> On Mon, Nov 22, 2021 at 02:51:36PM +0400, Jordan Vrtanoski wrote:
> > Hi,
> >     After bisecting, the regression defect was introduced in 5.4.90 with the following patch:
> > "[PATCH net v3] net: mvpp2: disable force link UP during port init procedure”
> > 
> >     The patch is changing the configuration of the port during the initialisation of MVPP22_XLG_CTRL0_REG, which
> > on ClearFog GT 8K is preventing the MVPP2 to properly start the MAC after the transceiver is detected. After reverting 
> > the patch, the transceiver works properly.
> 
> Right, the problem will be 875082244853 ("net: mvpp2: disable force
> link UP during port init procedure") that has been backported to
> kernels that it shouldn't have been applied to.
> 
> There is a subtle interaction between that commit and development work
> leading up to it that wasn't obvious during the review. Specifically,
> any kernel without fefeae73ac7a ("net: mvpp2: ensure the port is forced
> down while changing modes") will now be broken.
> 
> However, fefeae73ac7a is development work, and so can't be backported.
> 
> Adding stable to this thread so they're aware of the issue.

I've now reverted the commit in the 5.4.y tree.

thanks,

greg k-h