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ata: Use 64-bit timekeeping

PATCH Applied Tina Ruchandani 3 participants 3 messages Jan 27, 2015 libata

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Tina Ruchandani

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#0 lore raw

PATCH v3 1/1 ata: Use 64-bit timekeeping

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 <[email protected]>
Signed-off-by Tina Ruchandani <[email protected]>

---
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(-)
drivers/ata/pata_pdc2027x.c +5 -5
index 4d06a5c..dca8251 100644
@@ -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);
Signature · 1 line
2.2.0.rc0.207.ga3a616c
Reviewed-by on v3 1/1
#1 lore raw
Quoted 8 lines · 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 <[email protected]>
Signed-off-by Tina Ruchandani <[email protected]>

Looks great,

Reviewed-by Arnd Bergmann <[email protected]>
Applied
#2 lore raw
In reply to Tina Ruchandani
Quoted 8 lines · 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 <[email protected]>
Signed-off-by Tina Ruchandani <[email protected]>

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

Thanks.

Signature · 1 line
tejun