On 2018년 11월 22일 03:01, Lukasz Luba wrote:
> 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.
Please remove the duplicate information about patch history.
>
> Suggested-by: Tobias Jakobi <tjakobi@xxxxxxxxxxxxxxxxxxxxx>
> Suggested-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
> Signed-off-by: Lukasz Luba <l.luba@xxxxxxxxxxxxxxxxxxx>
> ---
> 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;
Move 'ret' definition under 'if (devfreq->suspend_freq) {'
because 'ret' is used if suspend_freq isn't zero.
> + 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);
Remove the 'prev_freq' parameter.
> + if (ret)
> + return ret;
> +
> + devfreq->resume_freq = prev_freq;
As I commented on patch2, if devfreq_set_taget save the current frequency
to 'devfreq->resume_freq', this line is not needed.
> + }
> +
> + 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;
Move 'ret' definition under 'if (devfreq->suspend_freq) {'
because 'ret' is used if suspend_freq isn't zero.
> + unsigned long prev_freq;
Remove prev_freq variable which is not used on this function.
After calling devfreq_set_target, prev_freq is not used.
> + 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);
Remove the 'prev_freq' parameter.
> + if (ret)
> + return ret;
> + }
> +
> if (!devfreq->governor)
> return 0;
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
