[PATCHv4 net-next 03/32] cxgb4: Rectify emitting messages about SGE Ingress DMA channels being potentially stuck

[Hariprasad Shenai <hariprasad@chelsio.com>]

From: Kumar Sanghvi <kumaras@chelsio.com>

Based on original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Kumar Sanghvi <kumaras@chelsio.com>
---
 drivers/net/ethernet/chelsio/cxgb4/cxgb4.h |  9 ++-
 drivers/net/ethernet/chelsio/cxgb4/sge.c   | 90 ++++++++++++++++++++++++------
 2 files changed, 79 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
index 509c976..50abe1d 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
@@ -556,8 +556,13 @@ struct sge {
 	u32 pktshift;               /* padding between CPL & packet data */
 	u32 fl_align;               /* response queue message alignment */
 	u32 fl_starve_thres;        /* Free List starvation threshold */
-	unsigned int starve_thres;
-	u8 idma_state[2];
+
+	/* State variables for detecting an SGE Ingress DMA hang */
+	unsigned int idma_1s_thresh;/* SGE same State Counter 1s threshold */
+	unsigned int idma_stalled[2];/* SGE synthesized stalled timers in HZ */
+	unsigned int idma_state[2]; /* SGE IDMA Hang detect state */
+	unsigned int idma_qid[2];   /* SGE IDMA Hung Ingress Queue ID */
+
 	unsigned int egr_start;
 	unsigned int ingr_start;
 	void *egr_map[MAX_EGRQ];    /* qid->queue egress queue map */
diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index 3a2ecd8..054bb03 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -93,6 +93,16 @@
  */
 #define TX_QCHECK_PERIOD (HZ / 2)
 
+/* SGE Hung Ingress DMA Threshold Warning time (in Hz) and Warning Repeat Rate
+ * (in RX_QCHECK_PERIOD multiples).  If we find one of the SGE Ingress DMA
+ * State Machines in the same state for this amount of time (in HZ) then we'll
+ * issue a warning about a potential hang.  We'll repeat the warning as the
+ * SGE Ingress DMA Channel appears to be hung every N RX_QCHECK_PERIODs till
+ * the situation clears.  If the situation clears, we'll note that as well.
+ */
+#define SGE_IDMA_WARN_THRESH (1 * HZ)
+#define SGE_IDMA_WARN_REPEAT (20 * RX_QCHECK_PERIOD)
+
 /*
  * Max number of Tx descriptors to be reclaimed by the Tx timer.
  */
@@ -2008,7 +2018,7 @@ irq_handler_t t4_intr_handler(struct adapter *adap)
 static void sge_rx_timer_cb(unsigned long data)
 {
 	unsigned long m;
-	unsigned int i, cnt[2];
+	unsigned int i, idma_same_state_cnt[2];
 	struct adapter *adap = (struct adapter *)data;
 	struct sge *s = &adap->sge;
 
@@ -2031,21 +2041,64 @@ static void sge_rx_timer_cb(unsigned long data)
 		}
 
 	t4_write_reg(adap, SGE_DEBUG_INDEX, 13);
-	cnt[0] = t4_read_reg(adap, SGE_DEBUG_DATA_HIGH);
-	cnt[1] = t4_read_reg(adap, SGE_DEBUG_DATA_LOW);
-
-	for (i = 0; i < 2; i++)
-		if (cnt[i] >= s->starve_thres) {
-			if (s->idma_state[i] || cnt[i] == 0xffffffff)
-				continue;
-			s->idma_state[i] = 1;
-			t4_write_reg(adap, SGE_DEBUG_INDEX, 11);
-			m = t4_read_reg(adap, SGE_DEBUG_DATA_LOW) >> (i * 16);
-			dev_warn(adap->pdev_dev,
-				 "SGE idma%u starvation detected for "
-				 "queue %lu\n", i, m & 0xffff);
-		} else if (s->idma_state[i])
-			s->idma_state[i] = 0;
+	idma_same_state_cnt[0] = t4_read_reg(adap, SGE_DEBUG_DATA_HIGH);
+	idma_same_state_cnt[1] = t4_read_reg(adap, SGE_DEBUG_DATA_LOW);
+
+	for (i = 0; i < 2; i++) {
+		u32 debug0, debug11;
+
+		/* If the Ingress DMA Same State Counter ("timer") is less
+		 * than 1s, then we can reset our synthesized Stall Timer and
+		 * continue.  If we have previously emitted warnings about a
+		 * potential stalled Ingress Queue, issue a note indicating
+		 * that the Ingress Queue has resumed forward progress.
+		 */
+		if (idma_same_state_cnt[i] < s->idma_1s_thresh) {
+			if (s->idma_stalled[i] >= SGE_IDMA_WARN_THRESH)
+				CH_WARN(adap, "SGE idma%d, queue%u,resumed after %d sec\n",
+					i, s->idma_qid[i],
+					s->idma_stalled[i]/HZ);
+			s->idma_stalled[i] = 0;
+			continue;
+		}
+
+		/* Synthesize an SGE Ingress DMA Same State Timer in the Hz
+		 * domain.  The first time we get here it'll be because we
+		 * passed the 1s Threshold; each additional time it'll be
+		 * because the RX Timer Callback is being fired on its regular
+		 * schedule.
+		 *
+		 * If the stall is below our Potential Hung Ingress Queue
+		 * Warning Threshold, continue.
+		 */
+		if (s->idma_stalled[i] == 0)
+			s->idma_stalled[i] = HZ;
+		else
+			s->idma_stalled[i] += RX_QCHECK_PERIOD;
+
+		if (s->idma_stalled[i] < SGE_IDMA_WARN_THRESH)
+			continue;
+
+		/* We'll issue a warning every SGE_IDMA_WARN_REPEAT Hz */
+		if (((s->idma_stalled[i] - HZ) % SGE_IDMA_WARN_REPEAT) != 0)
+			continue;
+
+		/* Read and save the SGE IDMA State and Queue ID information.
+		 * We do this every time in case it changes across time ...
+		 */
+		t4_write_reg(adap, SGE_DEBUG_INDEX, 0);
+		debug0 = t4_read_reg(adap, SGE_DEBUG_DATA_LOW);
+		s->idma_state[i] = (debug0 >> (i * 9)) & 0x3f;
+
+		t4_write_reg(adap, SGE_DEBUG_INDEX, 11);
+		debug11 = t4_read_reg(adap, SGE_DEBUG_DATA_LOW);
+		s->idma_qid[i] = (debug11 >> (i * 16)) & 0xffff;
+
+		CH_WARN(adap, "SGE idma%u, queue%u, maybe stuck state%u %dsecs (debug0=%#x, debug11=%#x)\n",
+			i, s->idma_qid[i], s->idma_state[i],
+			s->idma_stalled[i]/HZ, debug0, debug11);
+		t4_sge_decode_idma_state(adap, s->idma_state[i]);
+	}
 
 	mod_timer(&s->rx_timer, jiffies + RX_QCHECK_PERIOD);
 }
@@ -2756,8 +2809,9 @@ int t4_sge_init(struct adapter *adap)
 
 	setup_timer(&s->rx_timer, sge_rx_timer_cb, (unsigned long)adap);
 	setup_timer(&s->tx_timer, sge_tx_timer_cb, (unsigned long)adap);
-	s->starve_thres = core_ticks_per_usec(adap) * 1000000;  /* 1 s */
-	s->idma_state[0] = s->idma_state[1] = 0;
+	s->idma_1s_thresh = core_ticks_per_usec(adap) * 1000000;  /* 1 s */
+	s->idma_stalled[0] = 0;
+	s->idma_stalled[1] = 0;
 	spin_lock_init(&s->intrq_lock);
 
 	return 0;
-- 
1.8.4