spi: loopback-test: add elapsed time check

This adds checks whether the elapsed time is longer than the minimam
estimated time.  The estimated time is calculated with the total
transfer length per clock rate and optional spi_transfer.delay_usecs.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-loopback-test.c

@@ -20,6 +20,7 @@
 
 #include <linux/delay.h>
 #include <linux/kernel.h>
+#include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/list_sort.h>
 #include <linux/module.h>
@@ -479,6 +480,35 @@ static int spi_check_rx_ranges(struct spi_device *spi,
 	return ret;
 }
 
+static int spi_test_check_elapsed_time(struct spi_device *spi,
+				       struct spi_test *test)
+{
+	int i;
+	unsigned long long estimated_time = 0;
+	unsigned long long delay_usecs = 0;
+
+	for (i = 0; i < test->transfer_count; i++) {
+		struct spi_transfer *xfer = test->transfers + i;
+		unsigned long long nbits = BITS_PER_BYTE * xfer->len;
+
+		delay_usecs += xfer->delay_usecs;
+		if (!xfer->speed_hz)
+			continue;
+		estimated_time += div_u64(nbits * NSEC_PER_SEC, xfer->speed_hz);
+	}
+
+	estimated_time += delay_usecs * NSEC_PER_USEC;
+	if (test->elapsed_time < estimated_time) {
+		dev_err(&spi->dev,
+			"elapsed time %lld ns is shorter than minimam estimated time %lld ns\n",
+			test->elapsed_time, estimated_time);
+
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int spi_test_check_loopback_result(struct spi_device *spi,
 					  struct spi_message *msg,
 					  void *tx, void *rx)
@@ -817,12 +847,16 @@ int spi_test_execute_msg(struct spi_device *spi, struct spi_test *test,
 
 	/* only if we do not simulate */
 	if (!simulate_only) {
+		ktime_t start;
+
 		/* dump the complete message before and after the transfer */
 		if (dump_messages == 3)
 			spi_test_dump_message(spi, msg, true);
 
+		start = ktime_get();
 		/* run spi message */
 		ret = spi_sync(spi, msg);
+		test->elapsed_time = ktime_to_ns(ktime_sub(ktime_get(), start));
 		if (ret == -ETIMEDOUT) {
 			dev_info(&spi->dev,
 				 "spi-message timed out - reruning...\n");
@@ -848,6 +882,10 @@ int spi_test_execute_msg(struct spi_device *spi, struct spi_test *test,
 
 		/* run rx-buffer tests */
 		ret = spi_test_check_loopback_result(spi, msg, tx, rx);
+		if (ret)
+			goto exit;
+
+		ret = spi_test_check_elapsed_time(spi, test);
 	}
 
 	/* if requested or on error dump message (including data) */

drivers/spi/spi-test.h

@@ -75,6 +75,7 @@
  * @fill_option:      define the way how tx_buf is filled
  * @fill_pattern:     fill pattern to apply to the tx_buf
  *                    (used in some of the @fill_options)
+ * @elapsed_time:     elapsed time in nanoseconds
  */
 
 struct spi_test {
@@ -108,6 +109,7 @@ struct spi_test {
 #define FILL_TRANSFER_BYTE_32 11 /* fill with the transfer byte - 32 bit */
 #define FILL_TRANSFER_NUM     16 /* fill with the transfer number */
 	u32 fill_pattern;
+	unsigned long long elapsed_time;
 };
 
 /* default implementation for @spi_test.run_test */