ice: Don't reset and rebuild for Tx timeout on PFC enabled queue

When there's a Tx timeout for a queue which belongs to a PFC enabled TC,
then it's not because the queue is hung but because PFC is in action.

In PFC, peer sends a pause frame for a specified period of time when its
buffer threshold is exceeded (due to congestion). Netdev on the other
hand checks if ACK is received within a specified time for a TX packet, if
not, it'll invoke the tx_timeout routine.

Signed-off-by: Avinash JD <avinash.dayanand@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ice/ice_dcb_lib.c

@@ -62,6 +62,64 @@ u8 ice_dcb_get_ena_tc(struct ice_dcbx_cfg *dcbcfg)
 	return ena_tc;
 }
 
+/**
+ * ice_is_pfc_causing_hung_q
+ * @pf: pointer to PF structure
+ * @txqueue: Tx queue which is supposedly hung queue
+ *
+ * find if PFC is causing the hung queue, if yes return true else false
+ */
+bool ice_is_pfc_causing_hung_q(struct ice_pf *pf, unsigned int txqueue)
+{
+	u8 num_tcs = 0, i, tc, up_mapped_tc, up_in_tc = 0;
+	u64 ref_prio_xoff[ICE_MAX_UP];
+	struct ice_vsi *vsi;
+	u32 up2tc;
+
+	vsi = ice_get_main_vsi(pf);
+	if (!vsi)
+		return false;
+
+	ice_for_each_traffic_class(i)
+		if (vsi->tc_cfg.ena_tc & BIT(i))
+			num_tcs++;
+
+	/* first find out the TC to which the hung queue belongs to */
+	for (tc = 0; tc < num_tcs - 1; tc++)
+		if (ice_find_q_in_range(vsi->tc_cfg.tc_info[tc].qoffset,
+					vsi->tc_cfg.tc_info[tc + 1].qoffset,
+					txqueue))
+			break;
+
+	/* Build a bit map of all UPs associated to the suspect hung queue TC,
+	 * so that we check for its counter increment.
+	 */
+	up2tc = rd32(&pf->hw, PRTDCB_TUP2TC);
+	for (i = 0; i < ICE_MAX_UP; i++) {
+		up_mapped_tc = (up2tc >> (i * 3)) & 0x7;
+		if (up_mapped_tc == tc)
+			up_in_tc |= BIT(i);
+	}
+
+	/* Now that we figured out that hung queue is PFC enabled, still the
+	 * Tx timeout can be legitimate. So to make sure Tx timeout is
+	 * absolutely caused by PFC storm, check if the counters are
+	 * incrementing.
+	 */
+	for (i = 0; i < ICE_MAX_UP; i++)
+		if (up_in_tc & BIT(i))
+			ref_prio_xoff[i] = pf->stats.priority_xoff_rx[i];
+
+	ice_update_dcb_stats(pf);
+
+	for (i = 0; i < ICE_MAX_UP; i++)
+		if (up_in_tc & BIT(i))
+			if (pf->stats.priority_xoff_rx[i] > ref_prio_xoff[i])
+				return true;
+
+	return false;
+}
+
 /**
  * ice_dcb_get_mode - gets the DCB mode
  * @port_info: pointer to port info structure

drivers/net/ethernet/intel/ice/ice_dcb_lib.h

@@ -17,6 +17,8 @@
 void ice_dcb_rebuild(struct ice_pf *pf);
 u8 ice_dcb_get_ena_tc(struct ice_dcbx_cfg *dcbcfg);
 u8 ice_dcb_get_num_tc(struct ice_dcbx_cfg *dcbcfg);
+void ice_vsi_set_dcb_tc_cfg(struct ice_vsi *vsi);
+bool ice_is_pfc_causing_hung_q(struct ice_pf *pf, unsigned int txqueue);
 u8 ice_dcb_get_tc(struct ice_vsi *vsi, int queue_index);
 int
 ice_pf_dcb_cfg(struct ice_pf *pf, struct ice_dcbx_cfg *new_cfg, bool locked);
@@ -32,6 +34,20 @@ void
 ice_dcb_process_lldp_set_mib_change(struct ice_pf *pf,
 				    struct ice_rq_event_info *event);
 void ice_vsi_cfg_netdev_tc(struct ice_vsi *vsi, u8 ena_tc);
+
+/**
+ * ice_find_q_in_range
+ * @low: start of queue range for a TC i.e. offset of TC
+ * @high: start of queue for next TC
+ * @tx_q: hung_queue/tx_queue
+ *
+ * finds if queue 'tx_q' falls between the two offsets of any given TC
+ */
+static inline bool ice_find_q_in_range(u16 low, u16 high, unsigned int tx_q)
+{
+	return (tx_q >= low) && (tx_q < high);
+}
+
 static inline void
 ice_set_cgd_num(struct ice_tlan_ctx *tlan_ctx, struct ice_ring *ring)
 {
@@ -79,6 +95,13 @@ ice_tx_prepare_vlan_flags_dcb(struct ice_ring __always_unused *tx_ring,
 	return 0;
 }
 
+static inline bool
+ice_is_pfc_causing_hung_q(struct ice_pf __always_unused *pf,
+			  unsigned int __always_unused txqueue)
+{
+	return false;
+}
+
 #define ice_update_dcb_stats(pf) do {} while (0)
 #define ice_pf_dcb_recfg(pf) do {} while (0)
 #define ice_vsi_cfg_dcb_rings(vsi) do {} while (0)

drivers/net/ethernet/intel/ice/ice_hw_autogen.h

@@ -58,6 +58,7 @@
 #define PRTDCB_GENS				0x00083020
 #define PRTDCB_GENS_DCBX_STATUS_S		0
 #define PRTDCB_GENS_DCBX_STATUS_M		ICE_M(0x7, 0)
+#define PRTDCB_TUP2TC				0x001D26C0 /* Reset Source: CORER */
 #define GL_PREEXT_L2_PMASK0(_i)			(0x0020F0FC + ((_i) * 4))
 #define GL_PREEXT_L2_PMASK1(_i)			(0x0020F108 + ((_i) * 4))
 #define GLFLXP_RXDID_FLX_WRD_0(_i)		(0x0045c800 + ((_i) * 4))

drivers/net/ethernet/intel/ice/ice_main.c

@@ -5114,6 +5114,16 @@ static void ice_tx_timeout(struct net_device *netdev, unsigned int txqueue)
 
 	pf->tx_timeout_count++;
 
+	/* Check if PFC is enabled for the TC to which the queue belongs
+	 * to. If yes then Tx timeout is not caused by a hung queue, no
+	 * need to reset and rebuild
+	 */
+	if (ice_is_pfc_causing_hung_q(pf, txqueue)) {
+		dev_info(ice_pf_to_dev(pf), "Fake Tx hang detected on queue %u, timeout caused by PFC storm\n",
+			 txqueue);
+		return;
+	}
+
 	/* now that we have an index, find the tx_ring struct */
 	for (i = 0; i < vsi->num_txq; i++)
 		if (vsi->tx_rings[i] && vsi->tx_rings[i]->desc)

drivers/net/ethernet/intel/ice/ice_type.h

@@ -607,6 +607,8 @@ struct ice_eth_stats {
 	u64 tx_errors;			/* tepc */
 };
 
+#define ICE_MAX_UP	8
+
 /* Statistics collected by the MAC */
 struct ice_hw_port_stats {
 	/* eth stats collected by the port */