[PATCH net v2 2/9] net: axienet: Wait for PhyRstCmplt after core reset

[Robert Hancock]

On Thu, 2022-01-13 at 11:53 +0000, Radhey Shyam Pandey wrote:
> > -----Original Message-----
> > From: Robert Hancock <robert.hancock at calian.com>
> > Sent: Wednesday, January 12, 2022 11:07 PM
> > To: netdev at vger.kernel.org
> > Cc: Radhey Shyam Pandey <radheys at xilinx.com>; davem at davemloft.net;
> > kuba at kernel.org; linux-arm-kernel at lists.infradead.org; Michal Simek
> > <michals at xilinx.com>; ariane.keller at tik.ee.ethz.ch; daniel at iogearbox.net;
> > Robert Hancock <robert.hancock at calian.com>
> > Subject: [PATCH net v2 2/9] net: axienet: Wait for PhyRstCmplt after core
> > reset
> > 
> > When resetting the device, wait for the PhyRstCmplt bit to be set
> > in the interrupt status register before continuing initialization, to
> > ensure that the core is actually ready. The MgtRdy bit could also be
> > waited for, but unfortunately when using 7-series devices, the bit does
> 
> Just to understand - can you share 7- series design details.
> Based on documentation - This MgtRdy bit indicates if the TEMAC core is
> out of reset and ready for use. In systems that use an serial transceiver, 
> this bit goes to 1 when the serial transceiver is ready to use.

From what I saw, the bit behaved as described on ZynqMP where it would go to 1
during initialization, but on a Kintex-7 design with this core, the bit never
seemed to go to 1 until an actual link was established on the transceiver, so
it wasn't really usable in this situation.

> 
> Also if we don't wait for phy reset - what is the issue we are seeing?

This is more for the case of using an external PHY device - we shouldn't be
proceeding to MDIO initialization and potentially trying to talk to the PHY
when it is potentially still in reset..

> 
> > not appear to work as documented (it seems to behave as some sort of
> > link state indication and not just an indication the transceiver is
> > ready) so it can't really be relied on.
> > 
> > Fixes: 8a3b7a252dca9 ("drivers/net/ethernet/xilinx: added Xilinx AXI
> > Ethernet
> > driver")
> > Signed-off-by: Robert Hancock <robert.hancock at calian.com>
> > ---
> >  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > index f950342f6467..f425a8404a9b 100644
> > --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > @@ -516,6 +516,16 @@ static int __axienet_device_reset(struct axienet_local
> > *lp)
> >  		return ret;
> >  	}
> > 
> > +	/* Wait for PhyRstCmplt bit to be set, indicating the PHY reset has
> > finished */
> > +	ret = read_poll_timeout(axienet_ior, value,
> > +				value & XAE_INT_PHYRSTCMPLT_MASK,
> > +				DELAY_OF_ONE_MILLISEC, 50000, false, lp,
> > +				XAE_IS_OFFSET);
> > +	if (ret) {
> > +		dev_err(lp->dev, "%s: timeout waiting for PhyRstCmplt\n",
> > __func__);
> > +		return ret;
> > +	}
> > +
> >  	return 0;
> >  }
> > 
> > --
> > 2.31.1
-- 
Robert Hancock
Senior Hardware Designer, Calian Advanced Technologies
www.calian.com