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Date: Tue, 23 Jun 2020 10:56:46 +0100 From: Russell King - ARM Linux admin <linux@...linux.org.uk> To: Bartosz Golaszewski <bgolaszewski@...libre.com> Cc: Bartosz Golaszewski <brgl@...ev.pl>, Andrew Lunn <andrew@...n.ch>, Alexandre Belloni <alexandre.belloni@...tlin.com>, devicetree <devicetree@...r.kernel.org>, Vladimir Oltean <vladimir.oltean@....com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Fabien Parent <fparent@...libre.com>, Iyappan Subramanian <iyappan@...amperecomputing.com>, Quan Nguyen <quan@...amperecomputing.com>, Frank Rowand <frowand.list@...il.com>, Florian Fainelli <f.fainelli@...il.com>, Jakub Kicinski <kuba@...nel.org>, Vivien Didelot <vivien.didelot@...il.com>, Tom Lendacky <thomas.lendacky@....com>, Andrew Perepech <andrew.perepech@...iatek.com>, Stephane Le Provost <stephane.leprovost@...iatek.com>, Keyur Chudgar <keyur@...amperecomputing.com>, Jassi Brar <jaswinder.singh@...aro.org>, Claudiu Manoil <claudiu.manoil@....com>, Mark Brown <broonie@...nel.org>, "moderated list:ARM/Mediatek SoC..." <linux-mediatek@...ts.infradead.org>, Matthias Brugger <matthias.bgg@...il.com>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, netdev <netdev@...r.kernel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, Liam Girdwood <lgirdwood@...il.com>, Rob Herring <robh+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>, Pedro Tsai <pedro.tsai@...iatek.com>, "David S . Miller" <davem@...emloft.net>, Heiner Kallweit <hkallweit1@...il.com> Subject: Re: [PATCH 14/15] net: phy: add PHY regulator support On Tue, Jun 23, 2020 at 11:46:15AM +0200, Bartosz Golaszewski wrote: > wt., 23 cze 2020 o 11:43 Russell King - ARM Linux admin > <linux@...linux.org.uk> napisał(a): > > > > On Tue, Jun 23, 2020 at 11:41:11AM +0200, Bartosz Golaszewski wrote: > > > pon., 22 cze 2020 o 15:29 Russell King - ARM Linux admin > > > <linux@...linux.org.uk> napisał(a): > > > > > > > > > > [snip!] > > > > > > > > > > > This is likely to cause issues for some PHY drivers. Note that we have > > > > some PHY drivers which register a temperature sensor in the probe > > > > function, which means they can be accessed independently of the lifetime > > > > of the PHY bound to the network driver (which may only be while the > > > > network device is "up".) We certainly do not want hwmon failing just > > > > because the network device is down. > > > > > > > > That's kind of worked around for the reset stuff, because there are two > > > > layers to that: the mdio device layer reset support which knows nothing > > > > of the PHY binding state to the network driver, and the phylib reset > > > > support, but it is not nice. > > > > > > > > > > Regulators are reference counted so if the hwmon driver enables it > > > using mdio_device_power_on() it will stay on even after the PHY driver > > > calls phy_device_power_off(), right? Am I missing something? > > > > If that is true, you will need to audit the PHY drivers to add that. > > > > This change doesn't have any effect on devices which don't have a > regulator assigned in DT though. The one I'm adding in the last patch > is the first to use this. It's quality of implementation. Should we wait for someone else to make use of the new regulator support that has been added with a PHY that uses hwmon, and they don't realise that it breaks hwmon on it, and several kernel versions go by without it being noticed. It will only be a noticable issue when the associated network device is down, and that network device driver detaches from the PHY, so _is_ likely not to be noticed. Or should we do a small amount of work now to properly implement regulator support, which includes a trivial grep for "hwmon" amongst the PHY drivers, and add the necessary call to avoid the regulator being shut off. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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