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Date: Sun, 27 Mar 2022 14:02:29 +0530 From: Raag Jadav <raagjadav@...il.com> To: "Russell King (Oracle)" <linux@...linux.org.uk> Cc: Andrew Lunn <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Steen Hegelund <steen.hegelund@...rochip.com>, Bjarni Jonasson <bjarni.jonasson@...rochip.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] net: phy: mscc: enable MAC SerDes autonegotiation On Sat, Feb 26, 2022 at 04:31:57PM +0000, Russell King (Oracle) wrote: > On Sat, Feb 26, 2022 at 12:53:27PM +0530, Raag Jadav wrote: > > On Thu, Feb 24, 2022 at 10:48:57AM +0000, Russell King (Oracle) wrote: > > > Sorry for the late comment on this patch. > > > > > > On Sat, Feb 05, 2022 at 12:14:52PM +0530, Raag Jadav wrote: > > > > +static int vsc85xx_config_inband_aneg(struct phy_device *phydev, bool enabled) > > > > +{ > > > > + int rc; > > > > + u16 reg_val = 0; > > > > + > > > > + if (enabled) > > > > + reg_val = MSCC_PHY_SERDES_ANEG; > > > > + > > > > + mutex_lock(&phydev->lock); > > > > + > > > > + rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_3, > > > > + MSCC_PHY_SERDES_PCS_CTRL, MSCC_PHY_SERDES_ANEG, > > > > + reg_val); > > > > + > > > > + mutex_unlock(&phydev->lock); > > > > > > What is the reason for the locking here? > > > > > > phy_modify_paged() itself is safe due to the MDIO bus lock, so you > > > shouldn't need locking around it. > > > > > > > True. > > > > My initial thought was to have serialized access at PHY level, > > as we have multiple ports to work with. > > But I guess MDIO bus lock could do the job as well. > > The MDIO bus lock is the only lock that will guarantee that no other > users can nip onto the bus and possibly access your PHY in the middle > of an operation that requires more than one access to complete. Adding > local locking at PHY driver level does not give you those guarantees. > This is exactly why phy_modify() etc was added - because phy_read().. > phy_write() does not give that guarantee. > > As an example of something that could interfere - the userspace MII > ioctls. > > > I've gone through Vladimir's patches and they look more promising > > than this approach. > > Let me know if I could be of any help. > > I haven't seen them - so up to you. > Definitely worth a look. > Thanks. > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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