[PATCH v3] ata: Use 64-bit timekeeping

[PATCH v3] ata: Use 64-bit timekeeping

[Tina Ruchandani]

Function pdc_detect_pll_input_clock uses 'struct timeval'
to measure start and end times, used to compute the pll_clock value.
'struct timeval' on 32-bit systems will have its tv_sec field
overflow in year 2038 and beyond. This patch uses 'ktime_t'
(which uses 64 bits for seconds) for start and end times instead.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
---
Changes in v3:
	- Switch back to usec_elapsed being a 'long'.
Changes in v2:
	- Switch from timespec64 to ktime_t - more efficient.
	- Use ktime_us_delta to get usec_elapsed, it is more
	  efficient than manual computation of usecs from timespec64.
---
 drivers/ata/pata_pdc2027x.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/ata/pata_pdc2027x.c b/drivers/ata/pata_pdc2027x.c
index 4d06a5c..dca8251 100644
--- a/drivers/ata/pata_pdc2027x.c
+++ b/drivers/ata/pata_pdc2027x.c
@@ -28,6 +28,7 @@
 #include <linux/blkdev.h>
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/ktime.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_host.h>
 #include <scsi/scsi_cmnd.h>
@@ -605,7 +606,7 @@ static long pdc_detect_pll_input_clock(struct ata_host *host)
 	void __iomem *mmio_base = host->iomap[PDC_MMIO_BAR];
 	u32 scr;
 	long start_count, end_count;
-	struct timeval start_time, end_time;
+	ktime_t start_time, end_time;
 	long pll_clock, usec_elapsed;
 
 	/* Start the test mode */
@@ -616,14 +617,14 @@ static long pdc_detect_pll_input_clock(struct ata_host *host)
 
 	/* Read current counter value */
 	start_count = pdc_read_counter(host);
-	do_gettimeofday(&start_time);
+	start_time = ktime_get();
 
 	/* Let the counter run for 100 ms. */
 	mdelay(100);
 
 	/* Read the counter values again */
 	end_count = pdc_read_counter(host);
-	do_gettimeofday(&end_time);
+	end_time = ktime_get();
 
 	/* Stop the test mode */
 	scr = ioread32(mmio_base + PDC_SYS_CTL);
@@ -632,8 +633,7 @@ static long pdc_detect_pll_input_clock(struct ata_host *host)
 	ioread32(mmio_base + PDC_SYS_CTL); /* flush */
 
 	/* calculate the input clock in Hz */
-	usec_elapsed = (end_time.tv_sec - start_time.tv_sec) * 1000000 +
-		(end_time.tv_usec - start_time.tv_usec);
+	usec_elapsed = (long) ktime_us_delta(end_time, start_time);
 
 	pll_clock = ((start_count - end_count) & 0x3fffffff) / 100 *
 		(100000000 / usec_elapsed);
-- 
2.2.0.rc0.207.ga3a616c

Re: [PATCH v3] ata: Use 64-bit timekeeping

[Arnd Bergmann]

On Tuesday 27 January 2015 15:49:48 Tina Ruchandani wrote:
> Function pdc_detect_pll_input_clock uses 'struct timeval'
> to measure start and end times, used to compute the pll_clock value.
> 'struct timeval' on 32-bit systems will have its tv_sec field
> overflow in year 2038 and beyond. This patch uses 'ktime_t'
> (which uses 64 bits for seconds) for start and end times instead.
> 
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>

Looks great,

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH v3] ata: Use 64-bit timekeeping

[Tejun Heo]

On Tue, Jan 27, 2015 at 03:49:48PM +0530, Tina Ruchandani wrote:
> Function pdc_detect_pll_input_clock uses 'struct timeval'
> to measure start and end times, used to compute the pll_clock value.
> 'struct timeval' on 32-bit systems will have its tv_sec field
> overflow in year 2038 and beyond. This patch uses 'ktime_t'
> (which uses 64 bits for seconds) for start and end times instead.
> 
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>

Applied to libata/for-3.20 w/ subject updated to indicate that its
scope is pata_pdc2027x.

Thanks.

-- 
tejun