[PATCH 3/6] devfreq: add support for suspend/resume of a devfreq device
From: Lukasz Luba <hidden>
Date: 2018-11-21 18:02:47
Also in:
linux-devicetree, linux-pm, linux-samsung-soc, lkml
Subsystem:
device frequency (devfreq), the rest · Maintainers:
MyungJoo Ham, Kyungmin Park, Chanwoo Choi, Linus Torvalds
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 <redacted> Suggested-by: Chanwoo Choi <cw00.choi@samsung.com> Signed-off-by: Lukasz Luba <redacted> --- 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