linux-kernel - [PATCH 4.4 10/20] scsi: cxlflash: Improve EEH recovery time

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Date:   Fri,  5 May 2017 11:33:00 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Matthew R. Ochs" <mrochs@...ux.vnet.ibm.com>,
        Uma Krishnan <ukrishn@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: [PATCH 4.4 10/20] scsi: cxlflash: Improve EEH recovery time

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew R. Ochs <mrochs@...ux.vnet.ibm.com>

commit 05dab43230fdc0d14ca885b473a2740fe017ecb1 upstream.

When an EEH occurs during device initialization, the port timeout logic
can cause excessive delays as MMIO reads will fail. Depending on where
they are experienced, these delays can lead to a prolonged reset,
causing an unnecessary triggering of other timeout logic in the SCSI
stack or user applications.

To expedite recovery, the port timeout logic is updated to decay the
timeout at a much faster rate when in the presence of a likely EEH
frozen event.

Signed-off-by: Matthew R. Ochs <mrochs@...ux.vnet.ibm.com>
Acked-by: Uma Krishnan <ukrishn@...ux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/scsi/cxlflash/main.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -996,6 +996,8 @@ static int wait_port_online(__be64 __iom
 	do {
 		msleep(delay_us / 1000);
 		status = readq_be(&fc_regs[FC_MTIP_STATUS / 8]);
+		if (status == U64_MAX)
+			nretry /= 2;
 	} while ((status & FC_MTIP_STATUS_MASK) != FC_MTIP_STATUS_ONLINE &&
 		 nretry--);

@@ -1027,6 +1029,8 @@ static int wait_port_offline(__be64 __io
 	do {
 		msleep(delay_us / 1000);
 		status = readq_be(&fc_regs[FC_MTIP_STATUS / 8]);
+		if (status == U64_MAX)
+			nretry /= 2;
 	} while ((status & FC_MTIP_STATUS_MASK) != FC_MTIP_STATUS_OFFLINE &&
 		 nretry--);