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

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Message-ID: <20160112203002.GZ24441@pengutronix.de>
Date:	Tue, 12 Jan 2016 21:30:02 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	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>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	devicetree@...r.kernel.org, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Richard Cochran <richardcochran@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	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>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Philippe Reynes <tremyfr@...il.com>
Subject: Re: [PATCHv2 0/2] net: fec: Reset ethernet PHY whenever the enet_out
 clock is being enabled

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?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |