The patch adds support for handling suspend/resume process.
It uses atomic variables to make sure no race condition
affects the process.
The patch draws on Tobias Jakobi's work posted ~2 years ago, who tried to
solve issue with devfreq device's frequency during suspend/resume.
During the discussion on LKML some corner cases and comments appeared
related to the design. This patch address them keeping in mind suggestions
from Chanwoo Choi.
Suggested-by: Tobias Jakobi <tjak...@math.uni-bielefeld.de>
Suggested-by: Chanwoo Choi <cw00.c...@samsung.com>
Signed-off-by: Lukasz Luba <l.l...@partner.samsung.com>
---
drivers/devfreq/devfreq.c | 45 +++++++++++++++++++++++++++++++++++++++------
1 file changed, 39 insertions(+), 6 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index cf9c643..7e09de8 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -872,14 +872,33 @@ EXPORT_SYMBOL(devm_devfreq_remove_device);
*/
int devfreq_suspend_device(struct devfreq *devfreq)
{
- if (!devfreq)
- return -EINVAL;
+ int ret;
+ unsigned long prev_freq;
+ u32 flags = 0;
+
+ if (!devfreq)
+ return -EINVAL;
+
+ if (devfreq->governor) {
+ ret = devfreq->governor->event_handler(devfreq,
+ DEVFREQ_GOV_SUSPEND, NULL);
+ if (ret)
+ return ret;
+ }
- if (!devfreq->governor)
- return 0;
+ if (devfreq->suspend_freq) {
+ if (atomic_inc_return(&devfreq->suspend_count) > 1)
+ return 0;
- return devfreq->governor->event_handler(devfreq,
- DEVFREQ_GOV_SUSPEND, NULL);
+ ret = devfreq_set_target(devfreq, devfreq->suspend_freq,
+ &prev_freq, flags);
+ if (ret)
+ return ret;
+
+ devfreq->resume_freq = prev_freq;
+ }
+
+ return 0;
}
EXPORT_SYMBOL(devfreq_suspend_device);
@@ -893,9 +912,23 @@ EXPORT_SYMBOL(devfreq_suspend_device);
*/
int devfreq_resume_device(struct devfreq *devfreq)
{
+ int ret;
+ unsigned long prev_freq;
+ u32 flags = 0;
+
if (!devfreq)
return -EINVAL;
+ if (devfreq->suspend_freq) {
+ if (atomic_dec_return(&devfreq->suspend_count) >= 1)
+ return 0;
+
+ ret = devfreq_set_target(devfreq, devfreq->resume_freq,
+ &prev_freq, flags);
+ if (ret)
+ return ret;
+ }
+
if (!devfreq->governor)
return 0;
--
2.7.4
