dmatest: make dmatest threads freezable

Making dmatest threads freezable allows its use for system PM testing.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/dmatest.c

@@ -10,6 +10,7 @@
 #include <linux/delay.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
+#include <linux/freezer.h>
 #include <linux/init.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
@@ -251,6 +252,7 @@ static int dmatest_func(void *data)
 	int			i;
 
 	thread_name = current->comm;
+	set_freezable_with_signal();
 
 	ret = -ENOMEM;
 
@@ -305,7 +307,8 @@ static int dmatest_func(void *data)
 		dma_addr_t dma_srcs[src_cnt];
 		dma_addr_t dma_dsts[dst_cnt];
 		struct completion cmp;
-		unsigned long tmo = msecs_to_jiffies(timeout);
+		unsigned long start, tmo, end = 0 /* compiler... */;
+		bool reload = true;
 		u8 align = 0;
 
 		total_tests++;
@@ -404,7 +407,17 @@ static int dmatest_func(void *data)
 		}
 		dma_async_issue_pending(chan);
 
-		tmo = wait_for_completion_timeout(&cmp, tmo);
+		do {
+			start = jiffies;
+			if (reload)
+				end = start + msecs_to_jiffies(timeout);
+			else if (end <= start)
+				end = start + 1;
+			tmo = wait_for_completion_interruptible_timeout(&cmp,
+								end - start);
+			reload = try_to_freeze();
+		} while (tmo == -ERESTARTSYS);
+
 		status = dma_async_is_tx_complete(chan, cookie, NULL, NULL);
 
 		if (tmo == 0) {