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When compiling for i686, drivers/infiniband/hw/cxgb4/device.o 
fails to compile:

drivers/infiniband/hw/cxgb4/device.c: In function 'wr_log_show':
include/linux/ktime.h:84:36: error: 'prev_time.tv64' may be used uninitialized in this function [-Werror=maybe-uninitialized]
({ (ktime_t){ .tv64 = (lhs).tv64 - (rhs).tv64 }; })
^
drivers/infiniband/hw/cxgb4/device.c:133:10: note: 'prev_time.tv64' was declared here
ktime_t prev_time;
^
cc1: all warnings being treated as errors
make[5]: *** [drivers/infiniband/hw/cxgb4/device.o] Error 1

I don't know why x86_64 is compiling without this patch.
Compiler (gcc) version dependence?

diff -up ./drivers/infiniband/hw/cxgb4/device.c.tv64 ./drivers/infiniband/hw/cxgb4/device.c
--- ./drivers/infiniband/hw/cxgb4/device.c.tv64	2018-10-05 05:18:19.000000000 +0900
+++ ./drivers/infiniband/hw/cxgb4/device.c	2018-11-01 09:34:48.000000000 +0900
@@ -130,7 +130,7 @@ void c4iw_log_wr_stats(struct t4_wq *wq,
 static int wr_log_show(struct seq_file *seq, void *v)
 {
 	struct c4iw_dev *dev = seq->private;
-	ktime_t prev_time;
+	ktime_t prev_time = { .tv64 = 0 };
 	struct wr_log_entry *lep;
 	int prev_time_set = 0;
 	int idx, end;