[2/5] dmaengine: dmatest: Use fixed point div to calculate iops

From: Seraj Alijan <seraj.alijan@sondrel.com>
To: vkoul@kernel.org
Cc: dmaengine@vger.kernel.org, dan.j.williams@intel.com,
	james.hartley@sondrel.com, sifan.naeem@sondrel.com,
	ed.blake@sondrel.com, Seraj Alijan <seraj.alijan@sondrel.com>
Subject: [2/5] dmaengine: dmatest: Use fixed point div to calculate iops
Date: Fri, 24 Aug 2018 13:15:38 +0100	[thread overview]
Message-ID: <1535112941-7169-3-git-send-email-seraj.alijan@sondrel.com> (raw)

Use fixed point division to calculate iops to prevent reporting 0 iops
when operations last for longer than a second.

Signed-off-by: Seraj Alijan <seraj.alijan@sondrel.com>
---
 drivers/dma/dmatest.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index 8ce3b06..130f343 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -170,6 +170,14 @@ MODULE_PARM_DESC(channel, "Bus ID of the channel to test (default: any)");
 #define PATTERN_COUNT_MASK	0x1f
 #define PATTERN_MEMSET_IDX	0x01
 
+/* Fixed point arithmetic ops */
+#define FIXPT_SHIFT		8
+#define FIXPNT_MASK		0xFF
+#define FIXPT_TO_INT(a)	((a) >> FIXPT_SHIFT)
+#define INT_TO_FIXPT(a)	((a) << FIXPT_SHIFT)
+#define FIXPT_GET_FRAC(a)	((((a) & FIXPNT_MASK) * 100) >> FIXPT_SHIFT)
+#define FIXPT_DIV(a, b)	DIV_ROUND_CLOSEST((INT_TO_FIXPT(a)), (b))
+
 /* poor man's completion - we want to use wait_event_freezable() on it */
 struct dmatest_done {
 	bool			done;
@@ -446,13 +454,14 @@ static unsigned long long dmatest_persec(s64 runtime, unsigned int val)
 	}
 
 	per_sec *= val;
-	do_div(per_sec, runtime);
+	per_sec = FIXPT_DIV(per_sec, runtime);
+
 	return per_sec;
 }
 
 static unsigned long long dmatest_KBs(s64 runtime, unsigned long long len)
 {
-	return dmatest_persec(runtime, len >> 10);
+	return FIXPT_TO_INT(dmatest_persec(runtime, len >> 10));
 }
 
 /*
@@ -493,6 +502,7 @@ static int dmatest_func(void *data)
 	ktime_t			comparetime = 0;
 	s64			runtime = 0;
 	unsigned long long	total_len = 0;
+	unsigned long long	iops = 0;
 	u8			align = 0;
 	bool			is_memset = false;
 	dma_addr_t		*srcs;
@@ -833,9 +843,10 @@ static int dmatest_func(void *data)
 err_srcs:
 	kfree(pq_coefs);
 err_thread_type:
-	pr_info("%s: summary %u tests, %u failures %llu iops %llu KB/s (%d)\n",
+	iops = dmatest_persec(runtime, total_tests);
+	pr_info("%s: summary %u tests, %u failures %llu.%02llu iops %llu KB/s (%d)\n",
 		current->comm, total_tests, failed_tests,
-		dmatest_persec(runtime, total_tests),
+		FIXPT_TO_INT(iops), FIXPT_GET_FRAC(iops),
 		dmatest_KBs(runtime, total_len), ret);
 
 	/* terminate all transfers on specified channels */
