On Tue, May 26, 2020 at 12:20:10PM -0500, Jeremy Linton wrote:
> Hi,
>
> On 5/26/20 12:14 PM, Russell King - ARM Linux admin wrote:
> > On Tue, May 26, 2020 at 03:31:16PM +0100, Russell King wrote:
> > > Add support for probing MMDs above 7 for a valid devices-in-package
> > > specifier.
> > >
> > > Signed-off-by: Russell King <rmk+ker...@armlinux.org.uk>
> > > ---
> > > drivers/net/phy/phy_device.c | 39 ++++++++++++++++++++++++++++++++++--
> > > include/linux/phy.h | 2 ++
> > > 2 files changed, 39 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > > index 0d6b6ca66216..fa9164ac0f3d 100644
> > > --- a/drivers/net/phy/phy_device.c
> > > +++ b/drivers/net/phy/phy_device.c
> > > @@ -659,6 +659,28 @@ struct phy_device *phy_device_create(struct mii_bus
> > > *bus, int addr, u32 phy_id,
> > > }
> > > EXPORT_SYMBOL(phy_device_create);
> > > +/* phy_c45_probe_present - checks to see if a MMD is present in the
> > > package
> > > + * @bus: the target MII bus
> > > + * @prtad: PHY package address on the MII bus
> > > + * @devad: PHY device (MMD) address
> > > + *
> > > + * Read the MDIO_STAT2 register, and check whether a device is responding
> > > + * at this address.
> > > + *
> > > + * Returns: negative error number on bus access error, zero if no device
> > > + * is responding, or positive if a device is present.
> > > + */
> > > +static int phy_c45_probe_present(struct mii_bus *bus, int prtad, int
> > > devad)
> > > +{
> > > + int stat2;
> > > +
> > > + stat2 = mdiobus_c45_read(bus, prtad, devad, MDIO_STAT2);
> > > + if (stat2 < 0)
> > > + return stat2;
> > > +
> > > + return (stat2 & MDIO_STAT2_DEVPRST) == MDIO_STAT2_DEVPRST_VAL;
> > > +}
> > > +
> > > /* get_phy_c45_devs_in_pkg - reads a MMD's devices in package registers.
> > > * @bus: the target MII bus
> > > * @addr: PHY address on the MII bus
> > > @@ -709,12 +731,25 @@ static int get_phy_c45_ids(struct mii_bus *bus, int
> > > addr, u32 *phy_id,
> > > {
> > > const int num_ids = ARRAY_SIZE(c45_ids->device_ids);
> > > u32 *devs = &c45_ids->devices_in_package;
> > > - int i, phy_reg;
> > > + int i, ret, phy_reg;
> > > /* Find first non-zero Devices In package. Device zero is
> > > reserved
> > > * for 802.3 c45 complied PHYs, so don't probe it at first.
> > > */
> > > - for (i = 1; i < num_ids && *devs == 0; i++) {
> > > + for (i = 1; i < MDIO_MMD_NUM && *devs == 0; i++) {
> > > + if (i >= 8) {
> > > + /* Only probe for the devices-in-package if there
> > > + * is a PHY reporting as present here; this avoids
> > > + * picking up on PHYs that implement non-IEEE802.3
> > > + * compliant register spaces.
> > > + */
> > > + ret = phy_c45_probe_present(bus, addr, i);
> > > + if (ret < 0)
> > > + return -EIO;
> > > +
> > > + if (!ret)
> > > + continue;
> > > + }
> >
> > A second look at 802.3, this can't be done for all MMDs (which becomes
> > visible when I look at the results from the 88x3310.) Only MMDs 1, 2,
> > 3, 4, 5, 30 and 31 are defined to have this register with the "Device
> > Present" bit pair.
> >
>
> I'm not sure it helps, but my thought process following some of the
> discussion last night was:
>
> something to the effect:
>
> for (i = 1; i < MDIO_MMD_NUM && *devs == 0; i++) {
> + if (i & RESERVED_MMDS)
> + continue;
>
> where RESERVED_MMDS was a hardcoded bitfield matching the IEEE reserved
> MMDs. or maybe a "IGNORE_MMDS" which also includes BIT0 and other MMDs the
> code doesn't understand.
That seems to be walking into a mine field - which MMDs are reserved
depends on which revision of the IEEE 802.3 specification you look at:
Spec version Reserved MMDs
2012, 2015 0, 12-28
2018 0, 14-28
and as technology progresses, it's likely more MMDs will no longer be
reserved.
There is another problem: 802.3 explicitly defines the devices in
package registers for MMD 1, 2, 3, 4, 5, 6, 7, and 29, but then goes
on to say:
"Each MMD contains registers 5 and 6, as defined in Table 45-2."
which seems rather contradictory.
There is also the problem that some PHYs have different values
in their devices-in-package register for each MMD:
MMD devices-in-package
1,3,7 c000009a
4 4000001a
30 00000000 (device present = not present)
31 fffe0000 (device present = not present)
What fun. Thankfully, MMD1 will be read first, so it doesn't
cause us a problem.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up
