On 1/16/2015 5:47 PM, Florian Fainelli wrote: > Hi Ray, > > On 16/01/15 17:10, Ray Jui wrote: >> Hi, >> >> Our SoC, Cygnus, uses a generic MDC/MDIO controller to talk to various >> PHYs, including 2 x Ethernet GPHY, 2 x PCIe Serdes, and 3 x USB PHYs. In >> this case, how should I work out a generic PHY driver to handle this? > > Interesting, I have typically seen separate MDIO controllers for at > least Ethernet and USB/PCIe/SATA. > >> >> I notice that most generic PHY drivers are in drivers/phy/*, but >> Ethernet seems to have its own interface of talking to a PHY through >> MDIO (drivers/net/phy/*). > > That's right, the Ethernet PHY library predates the generic PHY library > from Kishon and they have little to no common ground. > >> >> I need a single driver to handle these so there isn't any race condition >> for this single MDIO access in our system. > > How about the following design: > > - you create a MDIO bus controller library in e.g: > drivers/phy/cygnus-mdio.c which offers generic generic read/write > operations with a prototype looking like this: > > int mdio_read(void *device, enum device_type, int reg, int addr); > - int mdio_write(void *device, enum device_type, int reg, int addr, int > value) > - where device_type is MDIO_DEV_SERDES or MDIO_DEV_GPHY > > - these reads and writes are protected by a local spinlock which is not > exposed to the caller, it just needs to know that it gets serialized > access to the controller > > - you write a MDIO controller in drivers/phy/ for the USB and PCIe PHYs > which uses this library and interfaces with Kishon's PHY Library operations > > - you create a MDIO bus controller driver in drivers/net/phy/ which also > uses this library and registers with Linux using mdiobus_register() > > This is imho the easiest way to achieve what you want here, however, you > could also stash all of what I describe above in a single MDIO bus > driver in drivers/phy/ and ifdef out what is relevant based on your > kernel configuration, up to you, there could be some tricky dependencies > to solve though. > Thanks, Florian. This makes sense to me.
Note this means I'll need to create public headers under include/linux for the mdio library. But yes, having a shared mdio library and protected with spinlock is the only way to guarantee serialized access to the mdio controller. Ray -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
