Re: [PATCH net 08/15] ice: E825: clear PHY_REG_TX_MEMORY_STATUS prior to soft reset

diff --git a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c
index d48eb3c618231..a3a9f7ce04d2b 100644
--- a/drivers/net/ethernet/intel/ice/ice_ptp_hw.c
+++ b/drivers/net/ethernet/intel/ice/ice_ptp_hw.c

@@ -1139,8 +1121,8 @@ static int ice_read_ptp_tstamp_eth56g(struct ice_hw *hw, u8 port, u8 idx,
  * internal PHYs of the 56G devices.
  *
  * To directly clear the contents of the timestamp block entirely, discarding
- * all timestamp data at once, software should instead use
- * ice_ptp_reset_ts_memory_quad_eth56g().
+ * all timestamp data at once, software should instead perform a PHY soft
+ * reset via ice_ptp_phy_soft_reset_eth56g().
  *
  * This function should only be called on an idx whose bit is set according to
  * ice_get_phy_tx_tstamp_ready().

@@ -1152,24 +1134,16 @@ static int ice_clear_ptp_tstamp_eth56g(struct ice_hw *hw, u8 port, u8 idx)
 static int ice_clear_ptp_tstamp_eth56g(struct ice_hw *hw, u8 port, u8 idx)
 {
 	u64 unused_tstamp;
-	u16 lo_addr;
 	int err;
 
-	/* Read the timestamp register to ensure the timestamp status bit is
-	 * cleared.
+	/* Per the PHY spec, reading the timestamp memory location is what
+	 * clears the entry's valid bit and its corresponding (read-only)
+	 * ts_memory_status bit.
 	 */
 	err = ice_read_ptp_tstamp_eth56g(hw, port, idx, &unused_tstamp);
 	if (err) {
 		ice_debug(hw, ICE_DBG_PTP, "Failed to read the PHY timestamp register for port %u, idx %u, err %d\n",
 			  port, idx, err);
-	}
-
-	lo_addr = (u16)PHY_TSTAMP_L(idx);
-
-	err = ice_write_port_mem_eth56g(hw, port, lo_addr, 0);
-	if (err) {
-		ice_debug(hw, ICE_DBG_PTP, "Failed to clear low PTP timestamp register for port %u, idx %u, err %d\n",
-			  port, idx, err);
 		return err;
 	}
 

@@ -1177,19 +1151,36 @@ static int ice_clear_ptp_tstamp_eth56g(struct ice_hw *hw, u8 port, u8 idx)
 }
 
 /**
- * ice_ptp_reset_ts_memory_eth56g - Clear all timestamps from the port block
+ * ice_ptp_clear_tx_memory_status_eth56g - Reset one port's Tx timestamp memory
  * @hw: pointer to the HW struct
+ * @port: port number to clear
+ *
+ * Fully reset a single PHY port's Tx timestamp memory. Per the PHY spec, the
+ * only way to clear a timestamp valid bit (and its read-only ts_memory_status
+ * bit) is to read the timestamp memory location, so read every entry for the
+ * port (two 32-bit reads each). This discards all timestamp data on the port,
+ * so it must only be used for a full reset; callers that must preserve
+ * in-flight timestamps clear individual indices via ice_clear_phy_tstamp().
+ *
+ * Due to interactions with an internal HW counter for the number of
+ * outstanding Tx timestamps, this *must* only be called as part of the
+ * ice_ptp_phy_soft_reset_eth56g() procedure. Otherwise, the internal counter
+ * may become out of sync and prevent new timestamp interrupts.
+ *
+ * Return: 0 on success, negative error code on failure to read the PHY.
  */
-static void ice_ptp_reset_ts_memory_eth56g(struct ice_hw *hw)
+static int ice_ptp_clear_tx_memory_status_eth56g(struct ice_hw *hw, u8 port)
 {
-	unsigned int port;
+	int err = 0;
+	u8 idx;
 
-	for (port = 0; port < hw->ptp.num_lports; port++) {
-		ice_write_ptp_reg_eth56g(hw, port, PHY_REG_TX_MEMORY_STATUS_L,
-					 0);
-		ice_write_ptp_reg_eth56g(hw, port, PHY_REG_TX_MEMORY_STATUS_U,
-					 0);
+	for (idx = 0; idx < INDEX_PER_PORT; idx++) {
+		err = ice_clear_ptp_tstamp_eth56g(hw, port, idx);
+		if (err)
+			return err;
 	}
+
+	return 0;
 }

@@ -2306,6 +2304,13 @@ int ice_ptp_phy_soft_reset_eth56g(struct ice_hw *hw, u8 port)
 	u32 global_val;
 	int err;
 
+	err = ice_ptp_clear_tx_memory_status_eth56g(hw, port);
+	if (err) {
+		ice_debug(hw, ICE_DBG_PTP, "Failed to clear PHY_REG_TX_MEMORY_STATUS for port %d, err %d\n",
+			  port, err);
+		return err;
+	}
+
 	err = ice_read_ptp_reg_eth56g(hw, port, PHY_REG_GLOBAL, &global_val);
 	if (err) {
 		ice_debug(hw, ICE_DBG_PTP, "Failed to read PHY_REG_GLOBAL for port %d, err %d\n",