netdev - Re: [PATCH v2] fsl/fman: Use random MAC address when none is given

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Date:   Thu, 5 Mar 2020 16:35:50 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Madalin Bucur <madalin.bucur@....com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] fsl/fman: Use random MAC address when none is given

On Thu, Mar 05, 2020 at 03:03:48PM +0000, Madalin Bucur wrote:
> > -----Original Message-----
> > From: Sascha Hauer <s.hauer@...gutronix.de>
> > Sent: Thursday, March 5, 2020 4:48 PM
> > To: Madalin Bucur <madalin.bucur@....com>
> > Cc: netdev@...r.kernel.org
> > Subject: Re: [PATCH v2] fsl/fman: Use random MAC address when none is
> > given
> > 
> > On Thu, Mar 05, 2020 at 01:38:01PM +0000, Madalin Bucur wrote:
> > > > -----Original Message-----
> > > > From: Sascha Hauer <s.hauer@...gutronix.de>
> > > > Sent: Thursday, March 5, 2020 2:34 PM
> > > > To: netdev@...r.kernel.org
> > > > Cc: Madalin Bucur <madalin.bucur@....com>; Sascha Hauer
> > > > <s.hauer@...gutronix.de>
> > > > Subject: [PATCH v2] fsl/fman: Use random MAC address when none is
> > given
> > > >
> > > > There's no need to fail probing when no MAC address is given in the
> > > > device tree, just use a random MAC address.
> > > >
> > > > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > > > ---
> > > >
> > > > Changes since v1:
> > > > - Remove printing of permanent MAC address
> > > >
> > > >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c   | 11 +++++++++--
> > > >  drivers/net/ethernet/freescale/fman/fman_memac.c |  4 ----
> > > >  drivers/net/ethernet/freescale/fman/mac.c        | 10 ++--------
> > > >  3 files changed, 11 insertions(+), 14 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > index fd93d542f497..fc117eab788d 100644
> > > > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > @@ -233,8 +233,15 @@ static int dpaa_netdev_init(struct net_device
> > > > *net_dev,
> > > >  	net_dev->features |= net_dev->hw_features;
> > > >  	net_dev->vlan_features = net_dev->features;
> > > >
> > > > -	memcpy(net_dev->perm_addr, mac_addr, net_dev->addr_len);
> > > > -	memcpy(net_dev->dev_addr, mac_addr, net_dev->addr_len);
> > > > +	if (is_valid_ether_addr(mac_addr)) {
> > > > +		dev_info(dev, "FMan MAC address: %pM\n", mac_addr);
> > > > +		memcpy(net_dev->perm_addr, mac_addr, net_dev->addr_len);
> > > > +		memcpy(net_dev->dev_addr, mac_addr, net_dev->addr_len);
> > > > +	} else {
> > > > +		eth_hw_addr_random(net_dev);
> > > > +		dev_info(dev, "Using random MAC address: %pM\n",
> > > > +			 net_dev->dev_addr);
> > > > +	}
> > >
> > > To make the HW MAC aware of the new random address you set in the
> > dpaa_eth,
> > > you also need to call mac_dev->change_addr() after
> > eth_hw_addr_random(), like
> > > it's done in dpaa_set_mac_address():
> > >
> > >         err = mac_dev->change_addr(mac_dev->fman_mac,
> > >                                    (enet_addr_t *)net_dev->dev_addr);
> > >
> > > This will write the new MAC address in the MAC HW registers.
> > 
> > Ok, I see.
> > 
> > So when I call mac_dev->change_addr() here in dpaa_netdev_init() it
> > means I can remove all the code setting the MAC address in hardware
> > before this point, right?
> 
> It's not an issue if you just write it here for the random address and leave
> the previous functionality in place.

No, it's not. It's only that the code becomes rather useless once we
overwrite the MAC address here anyway.

> Do you have a board to validate your changes?

I have a LS1046a based board, yes.

Sascha

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