On Tue, Mar 27, 2018 at 9:24 AM, Andrew Lunn <andrew@xxxxxxx> wrote: >> > This is a 2nd MDIO address, right? Can't you just append this to reg property? > > Hi Rob > > It is a sub address. > > There are two different MDIO addressing schemes. Clause 22 allowed for > 32 different addresses on an MDIO bus. Clause 45 extended that. You > have the existing 32 addresses for a package. However, within a > package, you can have 32 devices. Sounds similar to functions in PCI land (which are part of reg address). > You are supposed to be able to look are registers inside the package, > and it will tell you which devices in the packages are in use. You can > then look at those devices and figure out what they are using ID > registers. > > However some vendors get this wrong, they don't fill in the devices in > package information. So the generic probe code never finds them. We > need to pass it a hint, go looking at this specific device in the > package. If this is a rare case and something future devices should get right, then I'm more inclined to use 'dev-addr' rather than extending reg. > You can mix Clause 22 and Clause 45 on the same bus. Does DT allow two > different reg formats to be used at once? Can we have some reg > properties with a single value, and some with two values? I thought > #address-cells = <1> means there should be a single address in reg. #address-cells is how many cells (aka u32) it takes to store an address, not how many addresses you have. The number of addresses is (sizeof(reg) / 4) / (#address-cells + #size-cells). So yes, you can have different number of addresses for each device, but you can't have different sizes of addresses (e.g. 32-bit and 64-bit) in one bus. But I think in this case it would logically be 1 address with 2 cells because it is the port and device together that make up the address. If you did that, you'd have to define how to express a clause 22 device with 2 cells. You could either set a high bit in the first cell to indicate clause 45 address or use an illegal device address in the 2nd cell. However, the MDIO core would need to handle 2 address cells. If more than 1 address cell is an error currently, that causes a compatibility problem with new dtb and older kernels (but could be addressed with stable updates). Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
