From: Grzegorz Morys <grzegorz.morys@intel.com>
Date: Mon, 9 Oct 2017 12:38:04 -0700
Subject: IB/hfi1: Correct unnecessary acquisition of HW mutex
Patch-mainline: v4.15-rc1
Git-commit: b65c2045cc5089bd3cfacc9fad63798fded64226
References: bsc#1114685 FATE#325854

Avoid acquiring already acquired hardware mutex and releasing
the unacquired one as these are redundant operations.
Add printouts for such situations to help detect potential errors
within the driver.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Grzegorz Morys <grzegorz.morys@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/hw/hfi1/firmware.c |   19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/hfi1/firmware.c
+++ b/drivers/infiniband/hw/hfi1/firmware.c
@@ -1424,7 +1424,14 @@ int acquire_hw_mutex(struct hfi1_devdata
 	unsigned long timeout;
 	int try = 0;
 	u8 mask = 1 << dd->hfi1_id;
-	u8 user;
+	u8 user = (u8)read_csr(dd, ASIC_CFG_MUTEX);
+
+	if (user == mask) {
+		dd_dev_info(dd,
+			    "Hardware mutex already acquired, mutex mask %u\n",
+			    (u32)mask);
+		return 0;
+	}
 
 retry:
 	timeout = msecs_to_jiffies(HM_TIMEOUT) + jiffies;
@@ -1455,7 +1462,15 @@ retry:
 
 void release_hw_mutex(struct hfi1_devdata *dd)
 {
-	write_csr(dd, ASIC_CFG_MUTEX, 0);
+	u8 mask = 1 << dd->hfi1_id;
+	u8 user = (u8)read_csr(dd, ASIC_CFG_MUTEX);
+
+	if (user != mask)
+		dd_dev_warn(dd,
+			    "Unable to release hardware mutex, mutex mask %u, my mask %u\n",
+			    (u32)user, (u32)mask);
+	else
+		write_csr(dd, ASIC_CFG_MUTEX, 0);
 }
 
 /* return the given resource bit(s) as a mask for the given HFI */