On Fri, Feb 28, 2020 at 07:02:26PM +0100, Michael Walle wrote:

+static int at8031_rtc_adjust(struct phy_device *phydev, s64 delta)
+{
+	struct timespec64 ts = ns_to_timespec64(delta);
+	int ret;

Here the 'ts' is written in multiple steps,

+	ret = phy_write_mmd(phydev, MDIO_MMD_PCS,
+			    AT8031_MMD3_RTC_OFFSET_SEC_2,
+			    (ts.tv_sec >> 32) & 0xffff);
+	if (ret)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_PCS,
+			    AT8031_MMD3_RTC_OFFSET_SEC_1,
+			    (ts.tv_sec >> 16) & 0xffff);
+	if (ret)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_PCS,
+			    AT8031_MMD3_RTC_OFFSET_SEC_0,
+			    ts.tv_sec & 0xffff);
+	if (ret)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_PCS,
+			    AT8031_MMD3_RTC_OFFSET_NSEC_1,
+			    (ts.tv_nsec >> 16) & 0xffff);
+	if (ret)
+		return ret;
+
+	ret = phy_write_mmd(phydev, MDIO_MMD_PCS,
+			    AT8031_MMD3_RTC_OFFSET_NSEC_0,
+			    ts.tv_nsec & 0xffff);
+	if (ret)
+		return ret;
+
+	return phy_write_mmd(phydev, MDIO_MMD_PCS, AT8031_MMD3_RTC_ADJUST,
+			     AT8031_RTC_ADJUST);
+}

...

+static int at8031_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
+{
+	struct at803x_priv *priv =
+		container_of(ptp, struct at803x_priv, ptp_info);
+	struct phy_device *phydev = priv->phydev;
+
+	return at8031_rtc_adjust(phydev, delta);
+}

... and here there is no locking.  You would need a mutex here and
elsewhere to prevent multiple readers/writers from accessing the
device registers asynchronously.

(I know this is a just a RFC and that there are bigger problems with
the HW, but just saying.)

Thanks,
Richard