From: andrew@lunn.ch (Andrew Lunn) Date: Mon, 19 Nov 2018 16:28:30 +0100 Subject: [PATCH net-next v3 1/6] net: phy: mscc: migrate to phy_select/restore_page functions In-Reply-To: References: <20181008100728.24959-1-quentin.schulz@bootlin.com> <20181008100728.24959-2-quentin.schulz@bootlin.com> <20181119151057.GC26852@lunn.ch> Message-ID: <20181119152830.GE26852@lunn.ch> To: linux-riscv@lists.infradead.org List-Id: linux-riscv.lists.infradead.org On Mon, Nov 19, 2018 at 04:13:10PM +0100, Andreas Schwab wrote: > On Nov 19 2018, Andrew Lunn wrote: > > > On Mon, Nov 19, 2018 at 03:57:17PM +0100, Andreas Schwab wrote: > >> On Okt 08 2018, Quentin Schulz 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. Thanks Andrew