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

Parthiban.Veerasooran
2024-03-18T11:01:45Z

Hi Andrew,

On 08/03/24 7:03 pm, Andrew Lunn wrote:
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>
>> 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
Sure will add it in the mdio.h file.
>
>> /* 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.
Ah ok, I will use switch here.
>
>>
>> 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.
Sure, I will use -EOPNOTSUPP in the next version instead of -ENOTSUPP.
>
>> 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.
Ah ok, will return the error code from oa_tc6_read_register() in the
next version.

Best regards,
Parthiban V
>
> Andrew
>