From mboxrd@z Thu Jan 1 00:00:00 1970 From: ulf.hansson@linaro.org (Ulf Hansson) Date: Thu, 21 Apr 2016 12:34:02 +0200 Subject: [PATCH] PM / Runtime: Defer resuming of the device in pm_runtime_force_resume() Message-ID: <1461234842-22820-1-git-send-email-ulf.hansson@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org When the pm_runtime_force_suspend|resume() helpers were invented, we still had CONFIG_PM_RUNTIME and CONFIG_PM_SLEEP as separate Kconfig options. To make sure these helpers worked for all combinations and without introducing too much of complexity, the device was always resumed in pm_runtime_force_resume(). More precisely, when CONFIG_PM_SLEEP was set and CONFIG_PM_RUNTIME was unset, we needed to resume the device as the subsystem/driver couldn't rely on using runtime PM to do it. As the CONFIG_PM_RUNTIME option was merged into CONFIG_PM a while ago, it removed this combination, of using CONFIG_PM_SLEEP without the earlier CONFIG_PM_RUNTIME. For this reason we can now rely on the subsystem/driver to use runtime PM to resume the device, instead of forcing that to be done in all cases. In other words, let's defer this to a later point when it's actually needed. Signed-off-by: Ulf Hansson --- Note, this patch is based upon another not yet queued patch [1]. The reason is simply because that [1] is a more important patch as it fixes a problem. It was posted to linux-pm April 8th and I expect it (or a new revision of it) to be applied before $subject patch. [1] https://patchwork.kernel.org/patch/8782851 --- drivers/base/power/runtime.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index b746904..a190ca0 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1506,6 +1506,17 @@ int pm_runtime_force_resume(struct device *dev) goto out; } + /* + * The PM core increases the runtime PM usage count in the system PM + * prepare phase. If the count is greather than 1 at this point, someone + * else has also increased it. In such case, let's make sure to runtime + * resume the device as that is likely what is expected. In other case + * we trust the subsystem/driver to runtime resume the device when it's + * actually needed. + */ + if (atomic_read(&dev->power.usage_count) < 2) + goto out; + ret = pm_runtime_set_active(dev); if (ret) goto out; -- 1.9.1