linux-kernel - Re: [PATCHv2 0/2] net: fec: Reset ethernet PHY whenever the enet

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Date:   Mon, 26 Sep 2016 17:37:49 +0200
From:   Jörg Krause <joerg.krause@...edded.rocks>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Lothar Waßmann <LW@...O-electronics.de>
Cc:     Mark Rutland <mark.rutland@....com>, Andrew Lunn <andrew@...n.ch>,
        Stefan Agner <stefan@...er.ch>,
        Greg Ungerer <gerg@...inux.org>,
        Nimrod Andy <B38611@...escale.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Richard Cochran <richardcochran@...il.com>,
        devicetree@...r.kernel.org, Pawel Moll <pawel.moll@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Russell King - ARM Linux <linux@....linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Fabio Estevam <fabio.estevam@...escale.com>,
        Kevin Hao <haokexin@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Sascha Hauer <kernel@...gutronix.de>,
        Kumar Gala <galak@...eaurora.org>,
        Philippe Reynes <tremyfr@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCHv2 0/2] net: fec: Reset ethernet PHY whenever the
 enet_out clock is being enabled

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