igc: Add qbv_config_change_errors counter

Add ConfigChangeError(qbv_config_change_errors) when user try to set the
AdminBaseTime to past value while the current GCL is still running.

The ConfigChangeError counter should not be increased when a gate control
list is scheduled into the future.

User can use "ethtool -S <interface> | grep qbv_config_change_errors"
command to check the counter values.
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc.h

@@ -185,6 +185,7 @@ struct igc_adapter {
 	ktime_t base_time;
 	ktime_t cycle_time;
 	bool qbv_enable;
+	u32 qbv_config_change_errors;
 
 	/* OS defined structs */
 	struct pci_dev *pdev;

drivers/net/ethernet/intel/igc/igc_ethtool.c

@@ -67,6 +67,7 @@ static const struct igc_stats igc_gstrings_stats[] = {
 	IGC_STAT("rx_hwtstamp_cleared", rx_hwtstamp_cleared),
 	IGC_STAT("tx_lpi_counter", stats.tlpic),
 	IGC_STAT("rx_lpi_counter", stats.rlpic),
+	IGC_STAT("qbv_config_change_errors", qbv_config_change_errors),
 };
 
 #define IGC_NETDEV_STAT(_net_stat) { \

drivers/net/ethernet/intel/igc/igc_main.c

@@ -6049,6 +6049,7 @@ static int igc_tsn_clear_schedule(struct igc_adapter *adapter)
 
 	adapter->base_time = 0;
 	adapter->cycle_time = NSEC_PER_SEC;
+	adapter->qbv_config_change_errors = 0;
 
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *ring = adapter->tx_ring[i];

drivers/net/ethernet/intel/igc/igc_tsn.c

@@ -114,6 +114,7 @@ static int igc_tsn_disable_offload(struct igc_adapter *adapter)
 static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 {
 	struct igc_hw *hw = &adapter->hw;
+	bool tsn_mode_reconfig = false;
 	u32 tqavctrl, baset_l, baset_h;
 	u32 sec, nsec, cycle;
 	ktime_t base_time, systim;
@@ -226,6 +227,10 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 	}
 
 	tqavctrl = rd32(IGC_TQAVCTRL) & ~IGC_TQAVCTRL_FUTSCDDIS;
+
+	if (tqavctrl & IGC_TQAVCTRL_TRANSMIT_MODE_TSN)
+		tsn_mode_reconfig = true;
+
 	tqavctrl |= IGC_TQAVCTRL_TRANSMIT_MODE_TSN | IGC_TQAVCTRL_ENHANCED_QAV;
 
 	cycle = adapter->cycle_time;
@@ -239,6 +244,13 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 		s64 n = div64_s64(ktime_sub_ns(systim, base_time), cycle);
 
 		base_time = ktime_add_ns(base_time, (n + 1) * cycle);
+
+		/* Increase the counter if scheduling into the past while
+		 * Gate Control List (GCL) is running.
+		 */
+		if ((rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
+		    tsn_mode_reconfig)
+			adapter->qbv_config_change_errors++;
 	} else {
 		/* According to datasheet section 7.5.2.9.3.3, FutScdDis bit
 		 * has to be configured before the cycle time and base time.