netdev - Re: [PATCH][NET] several cleanups and bugfixes for fec.c: preserve MII/RMII setting in fec

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Message-ID: <20191.17573.87285.411253@ipc1.ka-ro>
Date:	Wed, 7 Dec 2011 11:49:09 +0100
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Shawn Guo <shawn.guo@...escale.com>
Cc:	<netdev@...r.kernel.org>, Shawn Guo <shawn.guo@...aro.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH][NET] several cleanups and bugfixes for fec.c: preserve
 MII/RMII setting in fec_stop()

Hi,

Shawn Guo writes:
> On Wed, Dec 07, 2011 at 11:42:28AM +0100, Lothar Waßmann wrote:
> > Hi,
> > 
> > Shawn Guo writes:
> > > On Tue, Dec 06, 2011 at 11:27:14AM +0100, Lothar Waßmann wrote:
> > > > Additionally to setting the ETHER_EN bit in FEC_ECNTRL the MII/RMII
> > > > setting in FEC_R_CNTRL needs to be preserved to keep the MII interface
> > > 
> > > s/MII/RMII?  From what I see from imx28 and imx6q RM, the reset state
> > > for this setting is MII mode.
> > > 
> > > > functional.
> > > > 
> > > > Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> > > > ---
> > > >  drivers/net/ethernet/freescale/fec.c |    5 ++++-
> > > >  1 files changed, 4 insertions(+), 1 deletions(-)
> > > 
> > > I assume this is fixing a problem you are seeing on imx28 only.
> > > Do you see the problem on imx53/51?
> > > 
> > No. i.MX53 uses the RMII gasket which is not affected by resetting the
> > controller. And imMX51 does not support RMII at all.
> > 
> > > > 
> > > > diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
> > > > index 11534b9..ab0afb5 100644
> > > > --- a/drivers/net/ethernet/freescale/fec.c
> > > > +++ b/drivers/net/ethernet/freescale/fec.c
> > > > @@ -515,6 +515,7 @@ fec_stop(struct net_device *ndev)
> > > >  	struct fec_enet_private *fep = netdev_priv(ndev);
> > > >  	const struct platform_device_id *id_entry =
> > > >  				platform_get_device_id(fep->pdev);
> > > > +	u32 rmii_mode = readl(fep->hwp + FEC_R_CNTRL) & (1 << 8);
> > > 
> > > This bit is only available on ENET (imx28 and imx6q).  Do we want to
> > > do the same thing for FEC (imx25/27/35/51/53)?
> > > 
> > No. AFAICT that's not necessary there.
> > 
> So you need to check it's actually running on ENET before accessing
> the bit.
> 
That's done in the place where the register is being written:
|	if (id_entry->driver_data & FEC_QUIRK_ENET_MAC) {
|		writel(2, fep->hwp + FEC_ECNTRL);
|		writel(rmii_mode, fep->hwp + FEC_R_CNTRL);
|	}

We could save one register read by doing the check also for the read,
but that would further complicate the code.


Lothar Waßmann
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