Re: [PATCHv2 0/2] net: fec: Reset ethernet PHY whenever the enet_out clock is being enabled

From: "Jörg Krause" <joerg.krause@embedded.rocks>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Lothar Waßmann" <LW@KARO-electronics.de>
Cc: Mark Rutland <mark.rutland@arm.com>, Andrew Lunn <andrew@lunn.ch>,
	Stefan Agner <stefan@agner.ch>, Greg Ungerer <gerg@uclinux.org>,
	Nimrod Andy <B38611@freescale.com>,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	Richard Cochran <richardcochran@gmail.com>,
	devicetree@vger.kernel.org, Pawel Moll <pawel.moll@arm.com>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Rob Herring <robh+dt@kernel.org>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	linux-arm-kernel@lists.infradead.org,
	Fabio Estevam <fabio.estevam@freescale.com>,
	Kevin Hao <haokexin@gmail.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Sascha Hauer <kernel@pengutronix.de>,
	Kumar Gala <galak@codeaurora.org>,
	Philippe Reynes <tremyfr@gmail.com>,
	Shawn Guo <shawnguo@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Lucas Stach <l.stach@pengutronix.de>
Subject: Re: [PATCHv2 0/2] net: fec: Reset ethernet PHY whenever the enet_out clock is being enabled
Date: Mon, 26 Sep 2016 17:37:49 +0200	[thread overview]
Message-ID: <1474904269.8465.2.camel@embedded.rocks> (raw)
In-Reply-To: <20160112203002.GZ24441@pengutronix.de>

Hi all,

On Tue, 2016-01-12 at 21:30 +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Tue, Jan 12, 2016 at 05:04:44PM +0100, Lothar Waßmann wrote:
> > 
> > > 
> > > On Tue, Jan 12, 2016 at 04:17:54PM +0100, Lothar Waßmann wrote:
> > > > 
> > > > This patchset fixes a regression introduced by
> > > > commit e8fcfcd5684a ("net: fec: optimize the clock management
> > > > to save power")
> > > > for ethernet PHYs that are using ENET_OUT as reference clock
> > > > (on i.MX6 or i.MX28)
> > > > 
> > > > Changes vs. v1:
> > > > - fixed reference to the commit that introduced the regression.
> > > > - dropped patch to use gpiod framework. This should be added
> > > > later,
> > > >   after the affected DTBs have been updated to specify the
> > > > correct
> > > >   gpio_flags.
> > > > 
> > > > Patch overview:
> > > > 1. cleanup patch to remove redundant NULL checks
> > > > 2. call fec_reset_phy() after the ENET_OUT clock has been
> > > > enabled
> > > 
> > > I definitely want to test these on my SolidRun boards before
> > > these get
> > > merged: the AR8035 on there is configured via pin-straps, and
> > > then
> > > further tweaked with PHY quirks.  Resetting with the iMX6 in the
> > > wrong state may result in the AR8035 being reconfigured (even
> > > jumping
> > > to a different MDIO address) and certainly would need the PHY
> > > quirks
> > > re-running.
> > > 
> > As far as I can tell, all SolidRun boards do not specify the
> > enet_out
> > clock in the dtb, so the PHY reset behaviour should be unaffected
> > by
> > this patch on those boards, since the additional fec_reset_phy()
> > call is
> > framed by:
> > if (fep->clk_enet_out) {
> > 	...
> > }
> > 
> > But verifying this explicitly is of course a good idea.
> 
> If the SolidRun boards don't do this, this doesn't mean it's safe in
> general. The problem is real, isn't it?

Anything new on this topic? I am facing the same issue with Linux
Kernel 4.7 and the MCSC LAN8720A on an i.MX28 board.

I found this patch on patchwork and it works for me.

Best regard
Jörg Krause