Re: [PATCH net-next v3 06/12] net: ethernet: oa_tc6: implement internal PHY initialization

Andrew Lunn
2024-03-08T13:32:59Z

> Ok, as per the table 6 in the spec, PHY C45 registers are mapped in the
> MMS like below,
>
> PHY – PCS Registers (MMD 3) ---> MMS 2
> PHY – PMA/PMD Registers (MMD 1) ---> MMS 3
> PHY – Vendor Specific and PLCA Registers (MMD 31) ---> MMS 4
> PHY – Auto-Negotiation Registers (MMD 7) ---> MMS 5
> PHY – Power Unit (MMD 13) ---> MMS 6
>
> MMD 13 for PHY - Power Unit is not defined in the mdio.h. So in the
> below code I have defined it locally (MDIO_MMD_POWER_UNIT). May be
> needed to do this in the mdio.h file when coming to this patch.

Yes, please add it to mdio.h

> /* PHY – Clause 45 registers memory map selector (MMS) as per table 6 in
> the OPEN Alliance specification.
> */
> #define OA_TC6_PHY_PCS_MMS2 2 /* MMD 3 */
> #define OA_TC6_PHY_PMA_PMD_MMS3 3 /* MMD 1 */
> #define OA_TC6_PHY_VS_PLCA_MMS4 4 /* MMD 31 */
> #define OA_TC6_PHY_AUTO_NEG_MMS5 5 /* MMD 7 */
> #define OA_TC6_PHY_POWER_UNIT_MMS6 6 /* MMD 13 */
>
> /* MDIO Manageable Device (MMD) for PHY Power Unit */
> #define MDIO_MMD_POWER_UNIT 13 /* PHY Power Unit */
>
> static int oa_tc6_mdiobus_read_c45(struct mii_bus *bus, int addr, int
> devnum, int regnum)
> {
>
> struct oa_tc6 *tc6 = bus->priv;
>
> u32 regval;
>
> bool ret;
>
> u32 mms;
>
>
>
> if (devnum == MDIO_MMD_PCS)
>
> mms = OA_TC6_PHY_PCS_MMS2;
>
> else if (devnum == MDIO_MMD_PMAPMD)
>
> mms = OA_TC6_PHY_PMA_PMD_MMS3;
>
> else if (devnum == MDIO_MMD_VEND2)
>
> mms = OA_TC6_PHY_VS_PLCA_MMS4;
>
> else if (devnum == MDIO_MMD_AN)
>
> mms = OA_TC6_PHY_AUTO_NEG_MMS5;
>
> else if (devnum == MDIO_MMD_POWER_UNIT)
>
> mms = OA_TC6_PHY_POWER_UNIT_MMS6;

I would probably use a switch statement.

>
> else
>
> return -ENOTSUPP;

802.3 says:

If a device supports the MDIO interface it shall respond to all
possible register addresses for the device and return a value of
zero for undefined and unsupported registers. Writes to undefined
registers and read-only registers shall have no effect. The
operation of an MMD shall not be affected by writes to reserved and
unsupported register bits, and such register bits shall return a
value of zero when read.

So maybe return 0. ENOTSUPP is wrong, that is an NFS only error
code. The generic one is EOPNOTSUPP. I would say -EOPNOTSUPP is also
O.K.

> ret = oa_tc6_read_register(tc6, (mms << 16) | regnum, &regval);
>
> if (ret)
>
> return -ENODEV;

oa_tc6_read_register() should return an error code, so return whatever
is returns. Don't overwrite error codes. It makes it harder to track
errors through the call stack.

Andrew