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Date:      Tue, 13 Oct 2015 17:20:47 +0000 (UTC)
From:      "Conrad E. Meyer" <cem@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r289232 - head/sys/dev/ntb/ntb_hw
Message-ID:  <201510131720.t9DHKlP3099189@repo.freebsd.org>
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Author: cem
Date: Tue Oct 13 17:20:47 2015
New Revision: 289232
URL: https://svnweb.freebsd.org/changeset/base/289232

Log:
  NTB: MFV 113bf1c9: BWD Link Recovery
  
  The BWD NTB device will drop the link if an error is encountered on the
  point-to-point PCI bridge.  The link will stay down until all errors are
  cleared and the link is re-established.  On link down, check to see if
  the error is detected, if so do the necessary housekeeping to try and
  recover from the error and reestablish the link.
  
  There is a potential race between the 2 NTB devices recovering at the
  same time.  If the times are synchronized, the link will not recover and
  the driver will be stuck in this loop forever.  Add a random interval to
  the recovery time to prevent this race.
  
  Authored by:	Jon Mason
  Obtained from:	Linux
  Sponsored by:	EMC / Isilon Storage Division

Modified:
  head/sys/dev/ntb/ntb_hw/ntb_hw.c

Modified: head/sys/dev/ntb/ntb_hw/ntb_hw.c
==============================================================================
--- head/sys/dev/ntb/ntb_hw/ntb_hw.c	Tue Oct 13 17:20:05 2015	(r289231)
+++ head/sys/dev/ntb/ntb_hw/ntb_hw.c	Tue Oct 13 17:20:47 2015	(r289232)
@@ -896,6 +896,7 @@ ntb_handle_heartbeat(void *arg)
 	if (rc != 0)
 		device_printf(ntb->device,
 		    "Error determining link status\n");
+
 	/* Check to see if a link error is the cause of the link down */
 	if (ntb->link_status == NTB_LINK_DOWN) {
 		status32 = ntb_reg_read(4, SOC_LTSSMSTATEJMP_OFFSET);
@@ -995,7 +996,15 @@ recover_soc_link(void *arg)
 	uint16_t status16;
 
 	soc_perform_link_restart(ntb);
-	pause("Link", SOC_LINK_RECOVERY_TIME * hz / 1000);
+
+	/*
+	 * There is a potential race between the 2 NTB devices recovering at
+	 * the same time.  If the times are the same, the link will not recover
+	 * and the driver will be stuck in this loop forever.  Add a random
+	 * interval to the recovery time to prevent this race.
+	 */
+	status32 = arc4random() % SOC_LINK_RECOVERY_TIME;
+	pause("Link", (SOC_LINK_RECOVERY_TIME + status32) * hz / 1000);
 
 	status32 = ntb_reg_read(4, SOC_LTSSMSTATEJMP_OFFSET);
 	if ((status32 & SOC_LTSSMSTATEJMP_FORCEDETECT) != 0)
@@ -1005,12 +1014,17 @@ recover_soc_link(void *arg)
 	if ((status32 & SOC_IBIST_ERR_OFLOW) != 0)
 		goto retry;
 
+	status32 = ntb_reg_read(4, ntb->reg_ofs.lnk_cntl);
+	if ((status32 & SOC_CNTL_LINK_DOWN) != 0)
+		goto out;
+
 	status16 = ntb_reg_read(2, ntb->reg_ofs.lnk_stat);
 	width = (status16 & NTB_LINK_WIDTH_MASK) >> 4;
 	speed = (status16 & NTB_LINK_SPEED_MASK);
 	if (ntb->link_width != width || ntb->link_speed != speed)
 		goto retry;
 
+out:
 	callout_reset(&ntb->heartbeat_timer, NTB_HB_TIMEOUT * hz,
 	    ntb_handle_heartbeat, ntb);
 	return;

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