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

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Message-ID: <20191.17172.493079.722098@ipc1.ka-ro>
Date:	Wed, 7 Dec 2011 11:42:28 +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 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.

> >  	/* We cannot expect a graceful transmit stop without link !!! */
> >  	if (fep->link) {
> > @@ -531,8 +532,10 @@ fec_stop(struct net_device *ndev)
> >  	writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
> >  
> >  	/* We have to keep ENET enabled to have MII interrupt stay working */
> > -	if (id_entry->driver_data & FEC_QUIRK_ENET_MAC)
> > +	if (id_entry->driver_data & FEC_QUIRK_ENET_MAC) {
> >  		writel(2, fep->hwp + FEC_ECNTRL);
> > +		writel(rmii_mode, fep->hwp + FEC_R_CNTRL);
> > +	}
> >  }
> 
> On imx6q, we have two bits, bit 6 and 8 of FEC_R_CNTRL, to select MII
> interface among MII, RMII and RGMII modes.  I'm not sure if we will
> run into the same problem for RGMII mode.  What's your test setup?
> I would try to reproduce it here.
> 
I'm using a TX28 which has the Ethernet PHY connected in RMII
mode. You should see the problem, if you unplug the ethernet cable on
a configured link. Without this patch the kernel will not detect when
the cable is plugged back in.


Lothar Waßmann
-- 
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