On Wed, Jun 24, 2020 at 05:57:19PM +0100, Russell King - ARM Linux admin wrote: > On Tue, Jun 23, 2020 at 06:27:06PM +0200, Bartosz Golaszewski wrote: > > wt., 23 cze 2020 o 11:56 Russell King - ARM Linux admin > > <linux@xxxxxxxxxxxxxxx> napisał(a): > > > > > > 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@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx> 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. > > > > > > > I'm not sure what the correct approach is here. Provide some helper > > that, when called, would increase the regulator's reference count even > > more to keep it enabled from the moment hwmon is registered to when > > the driver is detached? > > I think a PHY driver needs the utility to control this. We need to be > careful here with naming, because phylib is not the only code in the > kernel that uses the phy_ prefix. > > If we had runtime PM support for PHYs, with regulator support hooked > into runtime PM, then we already have standard interfaces that drivers > can use to control whether the device gets powered down. Other ideas: - using genpd outside of the SoC to provide power domain management. This is already hooked into runtime PM, but would need their agreement, a genpd provider written, and runtime PM added to phylib. - if we're going for some core driver model approach, then the driver model only knows when devices are bound and unbound to their driver, it knows nothing of phylib's attach/detach from the network interface. If we want to shut off power when a PHY is not attached, we would likely need some kind of interface to do that. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
