2020-06-09 20:51:46

by Stanley Chu

Subject: [PATCH v2] scsi: ufs: Fix imprecise time in devfreq window

Promise precision of devfreq windows by

1. Align time base of both devfreq_dev_status.total_time and
devfreq_dev_status.busy_time to ktime-based time.

2. Align below timelines,
- The beginning of devfreq window
- The beginning of busy time in new window
- The end of busy time in current window

Signed-off-by: Stanley Chu <[email protected]>
---
drivers/scsi/ufs/ufshcd.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index ad4fc829cbb2..04b79ca66fdf 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1314,6 +1314,7 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
unsigned long flags;
struct list_head *clk_list = &hba->clk_list_head;
struct ufs_clk_info *clki;
+ ktime_t curr_t;

if (!ufshcd_is_clkscaling_supported(hba))
return -EINVAL;
@@ -1321,6 +1322,7 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
memset(stat, 0, sizeof(*stat));

spin_lock_irqsave(hba->host->host_lock, flags);
+ curr_t = ktime_get();
if (!scaling->window_start_t)
goto start_window;

@@ -1332,18 +1334,17 @@ static int ufshcd_devfreq_get_dev_status(struct device *dev,
*/
stat->current_frequency = clki->curr_freq;
if (scaling->is_busy_started)
- scaling->tot_busy_t += ktime_to_us(ktime_sub(ktime_get(),
+ scaling->tot_busy_t += ktime_to_us(ktime_sub(curr_t,
scaling->busy_start_t));

- stat->total_time = jiffies_to_usecs((long)jiffies -
- (long)scaling->window_start_t);
+ stat->total_time = ktime_to_us(curr_t) - scaling->window_start_t;
stat->busy_time = scaling->tot_busy_t;
start_window:
- scaling->window_start_t = jiffies;
+ scaling->window_start_t = ktime_to_us(curr_t);
scaling->tot_busy_t = 0;

if (hba->outstanding_reqs) {
- scaling->busy_start_t = ktime_get();
+ scaling->busy_start_t = curr_t;
scaling->is_busy_started = true;
} else {
scaling->busy_start_t = 0;
--
2.18.0

2020-06-10 11:47:39

by Avri Altman

Subject: RE: [PATCH v2] scsi: ufs: Fix imprecise time in devfreq window

Hi Stanley,

>
>
> Promise precision of devfreq windows by
Promise -> guarantee / assure / verify that the?
Can you please also elaborate why the current window isn't accurate enough?
And add a fixes tag?

2020-06-10 16:51:42

by Stanley Chu

Subject: RE: [PATCH v2] scsi: ufs: Fix imprecise time in devfreq window

Hi Avri,

On Wed, 2020-06-10 at 11:43 +0000, Avri Altman wrote:
> Hi Stanley,
>
> >
> >
> > Promise precision of devfreq windows by
> Promise -> guarantee / assure / verify that the?
> Can you please also elaborate why the current window isn't accurate enough?
> And add a fixes tag?

OK! I will fix all of them in next version.

Thanks,
Stanley Chu