igc: allow BaseTime 0 enrollment for Qbv

Introduce qbv_enable flag in igc_adapter struct to store the Qbv on/off.
So this allow the BaseTime to enroll with zero value.

Fixes: 61572d5f ("igc: Simplify TSN flags handling")
Signed-off-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Signed-off-by: Tan Tee Min <tee.min.tan@linux.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

@@ -184,6 +184,7 @@ struct igc_adapter {
 
 	ktime_t base_time;
 	ktime_t cycle_time;
+	bool qbv_enable;
 
 	/* OS defined structs */
 	struct pci_dev *pdev;

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

@@ -6044,6 +6044,8 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 	u32 start_time = 0, end_time = 0;
 	size_t n;
 
+	adapter->qbv_enable = qopt->enable;
+
 	if (!qopt->enable)
 		return igc_tsn_clear_schedule(adapter);
 

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

@@ -36,7 +36,7 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
 {
 	unsigned int new_flags = adapter->flags & ~IGC_FLAG_TSN_ANY_ENABLED;
 
-	if (adapter->base_time)
+	if (adapter->qbv_enable)
 		new_flags |= IGC_FLAG_TSN_QBV_ENABLED;
 
 	if (is_any_launchtime(adapter))