From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Belloni Subject: Re: [PATCH net-next v3 1/6] net: phy: mscc: migrate to phy_select/restore_page functions Date: Mon, 19 Nov 2018 16:40:05 +0100 Message-ID: <20181119154005.GA8367@piout.net> References: <20181008100728.24959-1-quentin.schulz@bootlin.com> <20181008100728.24959-2-quentin.schulz@bootlin.com> <20181119151057.GC26852@lunn.ch> <20181119152830.GE26852@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Schwab , Quentin Schulz , davem@davemloft.net, f.fainelli@gmail.com, allan.nielsen@microchip.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, thomas.petazzoni@bootlin.com, linux-riscv@lists.infradead.org To: Andrew Lunn Return-path: Content-Disposition: inline In-Reply-To: <20181119152830.GE26852@lunn.ch> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 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. > 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