From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukasz Luba Subject: [PATCH 3/6] devfreq: add support for suspend/resume of a devfreq device Date: Wed, 21 Nov 2018 19:01:38 +0100 Message-ID: <1542823301-23563-4-git-send-email-l.luba@partner.samsung.com> References: <1542823301-23563-1-git-send-email-l.luba@partner.samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1542823301-23563-1-git-send-email-l.luba@partner.samsung.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org Cc: mark.rutland@arm.com, len.brown@intel.com, tony.luck@intel.com, keescook@chromium.org, cw00.choi@samsung.com, b.zolnierkie@samsung.com, gregkh@linuxfoundation.org, anton@enomsg.org, rjw@rjwysocki.net, robh+dt@kernel.org, Lukasz Luba , tjakobi@math.uni-bielefeld.de, kyungmin.park@samsung.com, myungjoo.ham@samsung.com, kgene@kernel.org, pavel@ucw.cz, ccross@android.com, krzk@kernel.org, m.szyprowski@samsung.com List-Id: linux-pm@vger.kernel.org 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 Suggested-by: Chanwoo Choi Signed-off-by: Lukasz Luba --- 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