[0/8] PM / devfreq: Add dev_pm_qos support

Message

Leonard Crestez Sept. 18, 2019, 12:18 a.m. UTC

Add dev_pm_qos notifiers to devfreq core in order to support frequency
limits via dev_pm_qos_add_request.

Unlike the rest of devfreq the dev_pm_qos frequency is measured in Khz,
this is consistent with current dev_pm_qos usage for cpufreq and
allows frequencies above 2Ghz (pm_qos expresses limits as s32).

Like with cpufreq the handling of min_freq/max_freq is moved to the
dev_pm_qos mechanism. Constraints from userspace are no longer clamped on
store, instead all values can be written and we only check against OPPs in a
new devfreq_get_freq_range function. This is consistent with the design of
dev_pm_qos.

Notifiers from pm_qos are executed under a single global dev_pm_qos_mtx and
need to take devfreq->lock. Notifier registration takes the same dev_pm_qos_mtx
so in order to prevent lockdep warnings it must be done outside devfreq->lock.
Current devfreq_add_device does *all* initialization under devfreq->lock
and that needs to be relaxed.

---

Changes since v4:
* Move more devfreq_add_device init ahead of device_register.
* Make devfreq_dev_release cleanup devices not yet in devfreq_list. This is
simpler than previous attempt to add to devfreq_list sonner.
* Take devfreq->lock in trans_stat_show
* Register dev_pm_opp notifier on devfreq parent dev (which has OPPs)
Link to v4: https://patchwork.kernel.org/cover/11114657/

Changes since v3:
* Cleanup locking and error-handling in devfreq_add_device
* Register notifiers after device registration but before governor start
* Keep the initialization of min_req/max_req ahead of device_register
because it's used for sysfs handling
* Use HZ_PER_KHZ instead of 1000
* Add kernel-doc comments
* Move OPP notifier to core
Link to v3: https://patchwork.kernel.org/cover/11104061/

Changes since v2:
* Handle sysfs via dev_pm_qos (in separate patch)
* Add locking to {min,max}_freq_show
* Fix checkpatch issues (long lines etc)
Link to v2: https://patchwork.kernel.org/patch/11084279/

Changes since v1:
* Add doxygen comments for min_nb/max_nb
* Remove notifiers on error/cleanup paths. Keep gotos simple by relying on
dev_pm_qos_remove_notifier ignoring notifiers which were not added.
Link to v1: https://patchwork.kernel.org/patch/11078475/

Leonard Crestez (8):
  PM / devfreq: Lock devfreq in trans_stat_show
  PM / devfreq: Don't fail devfreq_dev_release if not in list
  PM / devfreq: Move more initialization before registration
  PM / devfreq: Don't take lock in devfreq_add_device
  PM / devfreq: Introduce devfreq_get_freq_range
  PM / devfreq: Add dev_pm_qos support
  PM / devfreq: Use dev_pm_qos for sysfs min/max_freq
  PM / devfreq: Move opp notifier registration to core

 drivers/devfreq/devfreq.c    | 362 +++++++++++++++++++----------------
 drivers/devfreq/exynos-bus.c |   7 -
 drivers/devfreq/rk3399_dmc.c |   6 -
 include/linux/devfreq.h      |  22 +--
 4 files changed, 204 insertions(+), 193 deletions(-)