Messages in this thread | | | Date | Sun, 10 May 2020 16:52:50 +0200 | From | Andrew Lunn <> | Subject | Re: [PATCH net-next] net: phy: at803x: add cable diagnostics support |
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More of a note to self:
Now we have three implementations, we start to see bits of common code which could be pulled out and shared.
> +static bool at803x_cdt_fault_length_valid(u16 status) > +{ > + switch (FIELD_GET(AT803X_CDT_STATUS_STAT_MASK, status)) { > + case AT803X_CDT_STATUS_STAT_OPEN: > + case AT803X_CDT_STATUS_STAT_SHORT: > + return true; > + } > + return false; > +}
If we uses the netlink attribute values, not the PHY specific values, this could be put in the core.
> + > +static int at803x_cdt_fault_length(u16 status) > +{ > + int dt; > + > + /* According to the datasheet the distance to the fault is > + * DELTA_TIME * 0.824 meters. > + * > + * The author suspect the correct formula is: > + * > + * fault_distance = DELTA_TIME * (c * VF) / 125MHz / 2 > + * > + * where c is the speed of light, VF is the velocity factor of > + * the twisted pair cable, 125MHz the counter frequency and > + * we need to divide by 2 because the hardware will measure the > + * round trip time to the fault and back to the PHY. > + * > + * With a VF of 0.69 we get the factor 0.824 mentioned in the > + * datasheet. > + */ > + dt = FIELD_GET(AT803X_CDT_STATUS_DELTA_TIME_MASK, status); > + > + return (dt * 824) / 10; > +}
There seems to be a general consensus of 0.824 meters. So we could have helpers to convert back and forth in the core.
> +static int at803x_cable_test_start(struct phy_device *phydev) > +{ > + /* Enable auto-negotiation, but advertise no capabilities, no link > + * will be established. A restart of the auto-negotiation is not > + * required, because the cable test will automatically break the link. > + */ > + phy_write(phydev, MII_BMCR, BMCR_ANENABLE); > + phy_write(phydev, MII_ADVERTISE, ADVERTISE_CSMA); > + phy_write(phydev, MII_CTRL1000, 0);
Could be a genphy_ helper.
Lets get the code merged, when we can come back and do some refactoring.
Andrew
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