From 5fa87f166da8fe70c42b5e4838b1044abdc83230 Mon Sep 17 00:00:00 2001 From: Conrad Meyer Date: Tue, 13 Oct 2015 17:20:47 +0000 Subject: [PATCH] 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 --- sys/dev/ntb/ntb_hw/ntb_hw.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/sys/dev/ntb/ntb_hw/ntb_hw.c b/sys/dev/ntb/ntb_hw/ntb_hw.c index 606c43212bd..d6825bc85fb 100644 --- a/sys/dev/ntb/ntb_hw/ntb_hw.c +++ b/sys/dev/ntb/ntb_hw/ntb_hw.c @@ -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;