On 19/11/2018 16:28:30+0100, Andrew Lunn wrote: > On Mon, Nov 19, 2018 at 04:13:10PM +0100, Andreas Schwab wrote: > > On Nov 19 2018, Andrew Lunn <and...@lunn.ch> wrote: > > > > > On Mon, Nov 19, 2018 at 03:57:17PM +0100, Andreas Schwab wrote: > > >> On Okt 08 2018, Quentin Schulz <quentin.sch...@bootlin.com> wrote: > > >> > > >> > The Microsemi PHYs have multiple banks of registers (called pages). > > >> > Registers can only be accessed from one page, if we need a register > > >> > from > > >> > another page, we need to switch the page and the registers of all other > > >> > pages are not accessible anymore. > > >> > > > >> > Basically, to read register 5 from page 0, 1, 2, etc., you do the same > > >> > phy_read(phydev, 5); but you need to set the desired page beforehand. > > >> > > > >> > In order to guarantee that two concurrent functions do not change the > > >> > page, we need to do some locking per page. This can be achieved with > > >> > the > > >> > use of phy_select_page and phy_restore_page functions but > > >> > phy_write/read > > >> > calls in-between those two functions shall be replaced by their > > >> > lock-free alternative __phy_write/read. > > >> > > > >> > Let's migrate this driver to those functions. > > >> > > >> This has some serious locking problem. > > > > > > Hi Andreas > > > > > > Could you be more specific. Are you getting a deadlock? A WARN_ON? > > > > See the stack trace. That's where it hangs. > > So you never said it hangs. The stacktrace helps, but a description of > what actually happens also helps. And i expect Quentin has booted this > code lots of times and not had a hang. So some hits how to reproduce > it would also help. Maybe your kernel config? > > I'm interested because he is using the core mdio locking > primitives. If those are broken, i want to know. >
My first intuition is that he mac driver quentin is using does phy_connect when the interface is opened while macb is doing it at probe time. I didn't investigate but maybe this can help :) -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
