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NTB: MFV 113bf1c9: BWD Link Recovery

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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
This commit is contained in:
Conrad Meyer 2015-10-13 17:20:47 +00:00
parent 2b70dea602
commit 5fa87f166d
1 changed files with 15 additions and 1 deletions
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16
sys/dev/ntb/ntb_hw/ntb_hw.c
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@ -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;