[PATCH v3 1/2] firmware: exynos-acpm: use ktime APIs for timeout detection

[André Draszik]

acpm_dequeue_by_polling() uses a loop counter and assumes that each
iteration of the loop takes 20us. It may take longer, though, because
usleep_range() may sleep a different amount.

Switch to using ktime_get() / ktime_before() to detect the timeout
condition more reliably.

This change also makes the code easier to follow and it allows us to
adjust the sleep if necessary, without having to adjust the loop
counter exit condition.

Reviewed-by: Tudor Ambarus <tudor.ambarus at linaro.org>
Signed-off-by: André Draszik <andre.draszik at linaro.org>

---
v3:
* slightly reword commit message due to updated patch 2/2

v2:
* add missing ktime.h
* ktime_before() instead of !ktime_after() (Tudor)
---
 drivers/firmware/samsung/exynos-acpm.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
index a85b2dbdd9f0d7b1f327f54a0a283e4f32587a98..542eaff03f9e39422a8c5345ca75e05c1710a9ee 100644
--- a/drivers/firmware/samsung/exynos-acpm.c
+++ b/drivers/firmware/samsung/exynos-acpm.c
@@ -15,6 +15,7 @@
 #include <linux/firmware/samsung/exynos-acpm-protocol.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
+#include <linux/ktime.h>
 #include <linux/mailbox/exynos-message.h>
 #include <linux/mailbox_client.h>
 #include <linux/module.h>
@@ -32,8 +33,7 @@
 
 #define ACPM_PROTOCOL_SEQNUM		GENMASK(21, 16)
 
-/* The unit of counter is 20 us. 5000 * 20 = 100 ms */
-#define ACPM_POLL_TIMEOUT		5000
+#define ACPM_POLL_TIMEOUT_US		(100 * USEC_PER_MSEC)
 #define ACPM_TX_TIMEOUT_US		500000
 
 #define ACPM_GS101_INITDATA_BASE	0xa000
@@ -284,12 +284,13 @@ static int acpm_dequeue_by_polling(struct acpm_chan *achan,
 				   const struct acpm_xfer *xfer)
 {
 	struct device *dev = achan->acpm->dev;
-	unsigned int cnt_20us = 0;
+	ktime_t timeout;
 	u32 seqnum;
 	int ret;
 
 	seqnum = FIELD_GET(ACPM_PROTOCOL_SEQNUM, xfer->txd[0]);
 
+	timeout = ktime_add_us(ktime_get(), ACPM_POLL_TIMEOUT_US);
 	do {
 		ret = acpm_get_rx(achan, xfer);
 		if (ret)
@@ -300,11 +301,10 @@ static int acpm_dequeue_by_polling(struct acpm_chan *achan,
 
 		/* Determined experimentally. */
 		usleep_range(20, 30);
-		cnt_20us++;
-	} while (cnt_20us < ACPM_POLL_TIMEOUT);
+	} while (ktime_before(ktime_get(), timeout));
 
-	dev_err(dev, "Timeout! ch:%u s:%u bitmap:%lx, cnt_20us = %d.\n",
-		achan->id, seqnum, achan->bitmap_seqnum[0], cnt_20us);
+	dev_err(dev, "Timeout! ch:%u s:%u bitmap:%lx.\n",
+		achan->id, seqnum, achan->bitmap_seqnum[0]);
 
 	return -ETIME;
 }

-- 
2.49.0.395.g12beb8f557-goog