Horatiu.vultur:

Commit 85ede044f43d ("phy: mscc: Fix PTP for VSC8574 and VSC8572"),
which is a backport of upstream ea5df88aeca1, introduces a regression
on 6.6.y stable.

The commit changes the probe function for VSC8574 and VSC8572 from
vsc8574_probe to vsc8584_probe. However, vsc8584_probe on 6.6.y
contains a PHY ID check that rejects anything that is not VSC8584 revB:

    if ((phydev->phy_id & MSCC_DEV_REV_MASK) != VSC8584_REVB) {
        dev_err(..., "Only VSC8584 revB is supported.\n");
        return -ENOTSUPP;
    }

This causes VSC8574/VSC8572 to fail to probe:
logs:
Microsemi GE VSC8574 SyncE ff0d0000.ethernet-ffffffff:08: Only VSC8584 revB is supported.
Microsemi GE VSC8574 SyncE: probe of ff0d0000.ethernet-ffffffff:08 failed with error -524

On mainline, this check was removed by commit 1bc80d673087 ("phy: mscc:
Use PHY_ID_MATCH_EXACT for VSC8584, VSC8582, VSC8575, VSC856X"), which
was patch 1/2 of the same series. However, only patch 2/2 (ea5df88aeca1)
was backported to 6.6.y, without its prerequisite.

Who know why? 


Regards,
Guocai He