Hi Andrew, On Tue, Jul 07, 2020 at 04:19:18PM +0200, Andrew Lunn wrote: > On Mon, Jul 06, 2020 at 08:13:31PM +0200, Maxime Ripard wrote: > > I came across an issue today on an Allwinner board, but I believe it's a > > core issue. > > > > That board is using the stmac driver together with a phy that happens to > > have a reset GPIO, except that that GPIO will never be claimed, and the > > PHY will thus never work. > > > > You can find an example of such a board here: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/sun6i-a31-hummingbird.dts#n195 > > > > It looks like when of_mdiobus_register() will parse the DT, it will then > > call of_mdiobus_register_phy() for each PHY it encounters [1]. > > of_mdiobus_register_phy() will then if the phy doesn't have an > > ethernet-phy-id* compatible call get_phy_device() [2], and will later on > > call phy_register_device [3]. > > > > get_phy_device() will then call get_phy_id() [4], that will try to > > access the PHY through the MDIO bus [5]. > > > > The code that deals with the PHY reset line / GPIO is however only done > > in mdiobus_device_register, called through phy_device_register. Since > > this is happening way after the call to get_phy_device, our PHY might > > still very well be in reset if the bootloader hasn't put it out of reset > > and left it there. > > Hi Maxime > > If you look at the history of this code, > > commit bafbdd527d569c8200521f2f7579f65a044271be > Author: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx> > Date: Mon Dec 4 13:35:05 2017 +0100 > > phylib: Add device reset GPIO support > > you will see there is an assumption the PHY can be detected while in > reset. The reset was originally handled inside the at803x PHY driver > probe function, before it got moved into the core. > > What you are asking for it reasonable, but you have some history to > deal with, changing some assumptions as to what the reset is all > about. Thanks for the pointer. It looks to me from the commit log that the assumption was that a bootloader could leave the PHY into reset though? It starts with: > The PHY devices sometimes do have their reset signal (maybe even power > supply?) tied to some GPIO and sometimes it also does happen that a > boot loader does not leave it deasserted. This is exactly the case I was discussing. The bootloader hasn't used the PHY, and thus the PHY reset signal is still asserted? Maxime
