quoted

+static int marvell_vct7_cable_test_start(struct phy_device *phydev)
+{
+	int bmcr, bmsr, ret;
+
+	/* If auto-negotiation is enabled, but not complete, the cable
+	 * test never completes. So disable auto-neg.
+	 */
+	bmcr = phy_read(phydev, MII_BMCR);
+	if (bmcr < 0)
+		return bmcr;
+
+	bmsr = phy_read(phydev, MII_BMSR);
+
+	if (bmsr < 0)
+		return bmsr;
+
+	if (bmcr & BMCR_ANENABLE) {
+		ret =  phy_modify(phydev, MII_BMCR, BMCR_ANENABLE, 0);
+		if (ret < 0)
+			return ret;
+		ret = genphy_soft_reset(phydev);
+		if (ret < 0)
+			return ret;
+	}
+
+	/* If the link is up, allow it some time to go down */
+	if (bmsr & BMSR_LSTATUS)
+		msleep(1500);

Is it mandatory to wait 1.5s unconditionally or can we poll for link down?

Polling is fine. I think i got this from the Marvell SDK.

quoted

+
+	return phy_write_paged(phydev, MII_MARVELL_VCT7_PAGE,
+			       MII_VCT7_CTRL,
+			       MII_VCT7_CTRL_RUN_NOW |
+			       MII_VCT7_CTRL_CENTIMETERS);
+}
+
+static int marvell_vct7_distance_to_length(int distance, bool meter)
+{
+	if (meter)
+		distance *= 100;

I've never understood the use of the meter unit. If we always use
centimeters, we have 2^16 cm = 655m, shouldn't that be enough given
that the max cable length is 100m in TP ethernet? Also you hardcode
the unit to centimeters, so this should be superfluous, making this
function a noop.

Yes, it should never be used now. But i did use it initially, to see
if the results were different/better. It is a rather odd design, and
i'm wondering if some of the older PHYs only have meters? I guess i
should go look at the SDK.

quoted

+	return distance;
+}
+
+static bool marvell_vct7_distance_valid(int result)
+{
+	switch (result) {
+	case MII_VCT7_RESULTS_OPEN:
+	case MII_VCT7_RESULTS_SAME_SHORT:
+	case MII_VCT7_RESULTS_CROSS_SHORT:

btw on the BCM54140 I've observed, that if you have a intra-pair
short, the length is wrong; looks like it is twice the value it
should be.

Does the Marvell PHY report the correct value?

I've not tested that.

Chris, do you have results for this test?

quoted

+static int marvell_vct7_cable_test_report(struct phy_device *phydev)
+{
+	int pair0, pair1, pair2, pair3;
+	bool meter;
+	int ret;
+
+	ret = phy_read_paged(phydev, MII_MARVELL_VCT7_PAGE,
+			     MII_VCT7_RESULTS);
+	if (ret < 0)
+		return ret;
+
+	pair3 = (ret & MII_VCT7_RESULTS_PAIR3_MASK) >>
+		MII_VCT7_RESULTS_PAIR3_SHIFT;
+	pair2 = (ret & MII_VCT7_RESULTS_PAIR2_MASK) >>
+		MII_VCT7_RESULTS_PAIR2_SHIFT;
+	pair1 = (ret & MII_VCT7_RESULTS_PAIR1_MASK) >>
+		MII_VCT7_RESULTS_PAIR1_SHIFT;
+	pair0 = (ret & MII_VCT7_RESULTS_PAIR0_MASK) >>
+		MII_VCT7_RESULTS_PAIR0_SHIFT;

I'm sure you know FIELD_GET(), so there must be another
reason why you use mask and shift, consistency?

Consistency, and FIELD_GET() just looks odd, only taking a mask, not a
shift.

     Andrew