Messages in this thread | | | Date | Wed, 02 Aug 2023 17:33:20 +0200 | From | Michael Walle <> | Subject | Re: [PATCH net-next v3 02/11] net: phy: introduce phy_has_c45_registers() |
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Am 2023-08-01 17:57, schrieb Russell King (Oracle): > On Tue, Aug 01, 2023 at 05:20:22PM +0200, Michael Walle wrote: >> > In the case of the above (the code in __phy_read_mmd()), I wouldn't >> > at least initially change the test there. >> > >> > phydev->is_c45 will only be true if we probed the PHY using clause >> > 45 accesses. Thus, it will be set if "the bus supports clause 45 >> > accesses" _and_ "the PHY responds to those accesses". >> > >> > Changing that to only "the bus supports clause 45 accesses" means >> > that a PHY supporting only clause 22 access with indirect clause >> > 45 access then fails if it's used with a bus that supports both >> > clause 22 and clause 45 accesses. >> >> Yeah of course. It was more about the naming, but I just realized >> that with mdiobus_supports_c45() you can't access the original >> "is_c45" property of the PHY. So maybe this patch needs to be split >> into two to get rid of .is_c45: >> >> First a mechanical one: >> phy_has_c45_registers() { >> return phydev->is_c45; >> } > > Andrew's objection was that "phy_has_c45_registers" is a misnomer, and > suggested "_transfers" instead - because a PHY can have C45 registers > that are accessible via the indirect registers in C22 space.
I'm confused now. Andrew suggested to split it into four different functions:
phy_has_c22_registers() phy_has_c45_registers() phy_has_c22_transfers() phy_has_c45_transfers()
Without a functional change. That is, either return phydev->is_c45 or the inverse.
You seem to suggest to use either phy_supports_c45_transfers() or phy_has_c22_registers()
I'm not sure how to continue now.
> I'd go one further: > > static bool phy_supports_c45_transfers(struct phy_device *phydev) > { > return phydev->is_c45; > } > > Since that covers that (a) the bus needs to support C45 transfers and > (b) the PHY also needs to respond to C45 transfers. > > If we want to truly know whether a clause 22 PHY has clause 45 > registers, that's difficult to answer, because then you're into the > realms of "does this PHY implement the indirect access method" and > we haven't been keeping track of that for the PHYs we have drivers > for - many will do, but it's optional in clause 22. The problem is > that when it's not implemented, the registers could be serving some > other function. > >> phy_has_c22_registers() { >> return !phydev->is_c45; >> } > > The reverse is not true, as clause 45 PHYs can also support clause 22 > registers - from 802.3: > > "For cases where a single entity combines Clause 45 MMDs with Clause > 22 > registers, then the Clause 22 registers may be accessed using the > Clause > 45 electrical interface and the Clause 22 management frame structure." > > "Bit 5.0 is used to indicate that Clause 22 functionality has been > implemented within a Clause 45 electrical interface device." > > Therefore, this would more accurately describe when Clause 22 registers > are present for a PHY: > > static bool phy_has_c22_registers(struct phy_device *phydev) > { > /* If we probed the PHY without clause 45 accesses, then by > * definition, clause 22 registers must be present. > */ > if (!phydev->is_c45) > return true; > > /* If we probed the PHY with clause 45 accesses, clause 22 > * registers may be present if bit 0 in the Devices-in-pacakge > * register pair is set. > */ > return phydev->c45_ids.devices_in_package & BIT(0); > } > > Note that this doesn't take account of whether the bus supports clause > 22 register access - there are a number of MDIO buses that do not > support such accesses, and they may be coupled with a PHY that does > support clause 22 registers. > > I'm aware of a SFP with a Realtek PHY on that falls into this exact > case, and getting that working is progressing at the moment. > >> For all the places Andrew said it's correct. Leave all the >> other uses of .is_c45 as is for now and rework them in a >> later patch to use mdiobus_supports_{c22,c45}(). > > For the two cases in marvell10g and bcm84881, the test there for > is_c45 is purely to determine "was this ID found on a PHY supporting > clause 45 access" - however, in both cases, a check is made for MMDs > present in devices_in_package which will fail if the PHY wasn't > discovered in clause 45 mode. > > Note that 88x3310 does not support clause 22 access. I forget whether > bcm84881 does or not.
So a simple "phydev->is_c45" should be enough? Why do you test for the MMD presence bits?
-michael
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