RDMA/cxgb3: Doorbell overflow avoidance and recovery

T3 hardware doorbell FIFO overflows can cause application stalls due
to lost doorbell ring events.  This has been seen when running large
NP IMB alltoall MPI jobs.  The T3 hardware supports an xon/xoff-type
flow control mechanism to help avoid overflowing the HW doorbell FIFO.

This patch uses these interrupts to disable RDMA QP doorbell rings
when we near an overflow condition, and then turn them back on (and
ring all the active QP doorbells) when when the doorbell FIFO empties
out.  In addition if an doorbell ring is dropped by the hardware, the
code will now recover.

Design:

cxgb3:
- enable these DB interrupts
- in the interrupt handler, schedule work tasks to call the ULPs event
  handlers with the new events.
- ring all the qset txqs when an overflow is detected.

iw_cxgb3:
- disable db ringing on all active qps when we get the DB_FULL event
- enable db ringing on all active qps and ring all active dbs when we get
  the DB_EMPTY event
- On DB_DROP event:
       - disable db rings in the event handler
       - delay-schedule a work task which rings and enables the dbs on
         all active qps.
- in post_send and post_recv logic, don't ring the db if it's disabled.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

6 files changed, 93 insertions, 5 deletions

diff --git a/drivers/net/cxgb3/adapter.h b/drivers/net/cxgb3/adapter.h
index 3e8618b..4cd7f42 100644
--- a/drivers/net/cxgb3/adapter.h
+++ b/drivers/net/cxgb3/adapter.h
@@ -264,6 +264,10 @@ struct adapter {
 	struct work_struct fatal_error_handler_task;
 	struct work_struct link_fault_handler_task;
 
+	struct work_struct db_full_task;
+	struct work_struct db_empty_task;
+	struct work_struct db_drop_task;
+
 	struct dentry *debugfs_root;
 
 	struct mutex mdio_lock;
@@ -335,6 +339,7 @@ int t3_sge_alloc_qset(struct adapter *adapter, unsigned int id, int nports,
 int t3_get_desc(const struct sge_qset *qs, unsigned int qnum, unsigned int idx,
 		unsigned char *data);
 irqreturn_t t3_sge_intr_msix(int irq, void *cookie);
+extern struct workqueue_struct *cxgb3_wq;
 
 int t3_get_edc_fw(struct cphy *phy, int edc_idx, int size);
 
diff --git a/drivers/net/cxgb3/cxgb3_main.c b/drivers/net/cxgb3/cxgb3_main.c
index 89bec9c..37945fc 100644
--- a/drivers/net/cxgb3/cxgb3_main.c
+++ b/drivers/net/cxgb3/cxgb3_main.c
@@ -45,6 +45,7 @@
 #include <linux/firmware.h>
 #include <linux/log2.h>
 #include <linux/stringify.h>
+#include <linux/sched.h>
 #include <asm/uaccess.h>
 
 #include "common.h"
@@ -140,7 +141,7 @@ MODULE_PARM_DESC(ofld_disable, "whether to enable offload at init time or not");
  * will block keventd as it needs the rtnl lock, and we'll deadlock waiting
  * for our work to complete.  Get our own work queue to solve this.
  */
-static struct workqueue_struct *cxgb3_wq;
+struct workqueue_struct *cxgb3_wq;
 
 /**
  *	link_report - show link status and link speed/duplex
@@ -590,6 +591,19 @@ static void setup_rss(struct adapter *adap)
 		      V_RRCPLCPUSIZE(6) | F_HASHTOEPLITZ, cpus, rspq_map);
 }
 
+static void ring_dbs(struct adapter *adap)
+{
+	int i, j;
+
+	for (i = 0; i < SGE_QSETS; i++) {
+		struct sge_qset *qs = &adap->sge.qs[i];
+
+		if (qs->adap)
+			for (j = 0; j < SGE_TXQ_PER_SET; j++)
+				t3_write_reg(adap, A_SG_KDOORBELL, F_SELEGRCNTX | V_EGRCNTX(qs->txq[j].cntxt_id));
+	}
+}
+
 static void init_napi(struct adapter *adap)
 {
 	int i;
@@ -2754,6 +2768,42 @@ static void t3_adap_check_task(struct work_struct *work)
 	spin_unlock_irq(&adapter->work_lock);
 }
 
+static void db_full_task(struct work_struct *work)
+{
+	struct adapter *adapter = container_of(work, struct adapter,
+					       db_full_task);
+
+	cxgb3_event_notify(&adapter->tdev, OFFLOAD_DB_FULL, 0);
+}
+
+static void db_empty_task(struct work_struct *work)
+{
+	struct adapter *adapter = container_of(work, struct adapter,
+					       db_empty_task);
+
+	cxgb3_event_notify(&adapter->tdev, OFFLOAD_DB_EMPTY, 0);
+}
+
+static void db_drop_task(struct work_struct *work)
+{
+	struct adapter *adapter = container_of(work, struct adapter,
+					       db_drop_task);
+	unsigned long delay = 1000;
+	unsigned short r;
+
+	cxgb3_event_notify(&adapter->tdev, OFFLOAD_DB_DROP, 0);
+
+	/*
+	 * Sleep a while before ringing the driver qset dbs.
+	 * The delay is between 1000-2023 usecs.
+	 */
+	get_random_bytes(&r, 2);
+	delay += r & 1023;
+	set_current_state(TASK_UNINTERRUPTIBLE);
+	schedule_timeout(usecs_to_jiffies(delay));
+	ring_dbs(adapter);
+}
+
 /*
  * Processes external (PHY) interrupts in process context.
  */
@@ -3222,6 +3272,11 @@ static int __devinit init_one(struct pci_dev *pdev,
 	INIT_LIST_HEAD(&adapter->adapter_list);
 	INIT_WORK(&adapter->ext_intr_handler_task, ext_intr_task);
 	INIT_WORK(&adapter->fatal_error_handler_task, fatal_error_task);
+
+	INIT_WORK(&adapter->db_full_task, db_full_task);
+	INIT_WORK(&adapter->db_empty_task, db_empty_task);
+	INIT_WORK(&adapter->db_drop_task, db_drop_task);
+
 	INIT_DELAYED_WORK(&adapter->adap_check_task, t3_adap_check_task);
 
 	for (i = 0; i < ai->nports0 + ai->nports1; ++i) {
diff --git a/drivers/net/cxgb3/cxgb3_offload.h b/drivers/net/cxgb3/cxgb3_offload.h
index 670aa62..929c298 100644
--- a/drivers/net/cxgb3/cxgb3_offload.h
+++ b/drivers/net/cxgb3/cxgb3_offload.h
@@ -73,7 +73,10 @@ enum {
 	OFFLOAD_STATUS_UP,
 	OFFLOAD_STATUS_DOWN,
 	OFFLOAD_PORT_DOWN,
-	OFFLOAD_PORT_UP
+	OFFLOAD_PORT_UP,
+	OFFLOAD_DB_FULL,
+	OFFLOAD_DB_EMPTY,
+	OFFLOAD_DB_DROP
 };
 
 struct cxgb3_client {
diff --git a/drivers/net/cxgb3/regs.h b/drivers/net/cxgb3/regs.h
index 1b5327b..cb42353 100644
--- a/drivers/net/cxgb3/regs.h
+++ b/drivers/net/cxgb3/regs.h
@@ -254,6 +254,22 @@
 #define V_LOPIODRBDROPERR(x) ((x) << S_LOPIODRBDROPERR)
 #define F_LOPIODRBDROPERR    V_LOPIODRBDROPERR(1U)
 
+#define S_HIPRIORITYDBFULL    7
+#define V_HIPRIORITYDBFULL(x) ((x) << S_HIPRIORITYDBFULL)
+#define F_HIPRIORITYDBFULL    V_HIPRIORITYDBFULL(1U)
+
+#define S_HIPRIORITYDBEMPTY   6
+#define V_HIPRIORITYDBEMPTY(x) ((x) << S_HIPRIORITYDBEMPTY)
+#define F_HIPRIORITYDBEMPTY    V_HIPRIORITYDBEMPTY(1U)
+
+#define S_LOPRIORITYDBFULL    5
+#define V_LOPRIORITYDBFULL(x) ((x) << S_LOPRIORITYDBFULL)
+#define F_LOPRIORITYDBFULL    V_LOPRIORITYDBFULL(1U)
+
+#define S_LOPRIORITYDBEMPTY   4
+#define V_LOPRIORITYDBEMPTY(x) ((x) << S_LOPRIORITYDBEMPTY)
+#define F_LOPRIORITYDBEMPTY    V_LOPRIORITYDBEMPTY(1U)
+
 #define S_RSPQDISABLED    3
 #define V_RSPQDISABLED(x) ((x) << S_RSPQDISABLED)
 #define F_RSPQDISABLED    V_RSPQDISABLED(1U)
diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
index 318a018..9b43446 100644
--- a/drivers/net/cxgb3/sge.c
+++ b/drivers/net/cxgb3/sge.c
@@ -42,6 +42,7 @@
 #include "sge_defs.h"
 #include "t3_cpl.h"
 #include "firmware_exports.h"
+#include "cxgb3_offload.h"
 
 #define USE_GTS 0
 
@@ -2833,8 +2834,13 @@ void t3_sge_err_intr_handler(struct adapter *adapter)
 	}
 
 	if (status & (F_HIPIODRBDROPERR | F_LOPIODRBDROPERR))
-		CH_ALERT(adapter, "SGE dropped %s priority doorbell\n",
-			 status & F_HIPIODRBDROPERR ? "high" : "lo");
+		queue_work(cxgb3_wq, &adapter->db_drop_task);
+
+	if (status & (F_HIPRIORITYDBFULL | F_LOPRIORITYDBFULL))
+		queue_work(cxgb3_wq, &adapter->db_full_task);
+
+	if (status & (F_HIPRIORITYDBEMPTY | F_LOPRIORITYDBEMPTY))
+		queue_work(cxgb3_wq, &adapter->db_empty_task);
 
 	t3_write_reg(adapter, A_SG_INT_CAUSE, status);
 	if (status &  SGE_FATALERR)
diff --git a/drivers/net/cxgb3/t3_hw.c b/drivers/net/cxgb3/t3_hw.c
index 032cfe0..c38fc71 100644
--- a/drivers/net/cxgb3/t3_hw.c
+++ b/drivers/net/cxgb3/t3_hw.c
@@ -1432,7 +1432,10 @@ static int t3_handle_intr_status(struct adapter *adapter, unsigned int reg,
 		       F_IRPARITYERROR | V_ITPARITYERROR(M_ITPARITYERROR) | \
 		       V_FLPARITYERROR(M_FLPARITYERROR) | F_LODRBPARITYERROR | \
 		       F_HIDRBPARITYERROR | F_LORCQPARITYERROR | \
-		       F_HIRCQPARITYERROR)
+		       F_HIRCQPARITYERROR | F_LOPRIORITYDBFULL | \
+		       F_HIPRIORITYDBFULL | F_LOPRIORITYDBEMPTY | \
+		       F_HIPRIORITYDBEMPTY | F_HIPIODRBDROPERR | \
+		       F_LOPIODRBDROPERR)
 #define MC5_INTR_MASK (F_PARITYERR | F_ACTRGNFULL | F_UNKNOWNCMD | \
 		       F_REQQPARERR | F_DISPQPARERR | F_DELACTEMPTY | \
 		       F_NFASRCHFAIL)