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Thu, 7 Mar 2019 10:27:02 +0900 (KST) Received: from epsmtrp2.samsung.com (unknown [182.195.40.14]) by epcas1p1.samsung.com (KnoxPortal) with ESMTPA id 20190307012702epcas1p12c8946bc55d6fb216dc29e79f8c3452a~JiNtnko4r1110411104epcas1p1p; Thu, 7 Mar 2019 01:27:02 +0000 (GMT) Received: from epsmgms1p2new.samsung.com (unknown [182.195.42.42]) by epsmtrp2.samsung.com (KnoxPortal) with ESMTP id 20190307012702epsmtrp2869d031eef2954b4866782d2d71a36cc~JiNtmXPZp0643206432epsmtrp2T; Thu, 7 Mar 2019 01:27:02 +0000 (GMT) X-AuditID: b6c32a36-5c1ff7000000104d-73-5c80736633bd Received: from epsmtip1.samsung.com ( [182.195.34.30]) by epsmgms1p2new.samsung.com (Symantec Messaging Gateway) with SMTP id 6F.47.03601.663708C5; Thu, 7 Mar 2019 10:27:02 +0900 (KST) Received: from [10.113.221.102] (unknown [10.113.221.102]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20190307012702epsmtip134587974676293132bd22b00fcac85e6~JiNtZ-UKZ3161031610epsmtip1G; Thu, 7 Mar 2019 01:27:02 +0000 (GMT) Subject: Re: [PATCH] devfreq: Suspend all devices on system shutdown To: Pavel Machek , Marek Szyprowski Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-samsung-soc@vger.kernel.org, MyungJoo Ham , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , Lukasz Luba , Markus Reichl From: Chanwoo Choi Organization: Samsung Electronics Message-ID: <5621c652-6786-6bbb-ffbd-71567d8d882e@samsung.com> Date: Thu, 7 Mar 2019 10:27:02 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190306231014.GE7915@amd> Content-Language: en-US Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA02TWUwTURSGvZ122hIrY0E4olEYfFAiywDF0QBqQFMDMY0aQwymjnSkSLd0 ilF4oKiA4q4xYiFgFLCCBkUwiAIRikY0FAWDshhU3IhBIy6VB7XtSOTtO/cs//3vIsHkzXiQ JMtgYc0GRkfiPsJbncsiwndx1vSol7+j6Rul9SLa6bwupgetC+m+lnKcnjzmQHSps01Af3S4 EH3NMSKmhwrsOD3S3YWv8VEODucrG2oP48p7E3cFyuONtUhpr/spVk42LFLh27LjtSyjYc3B rCHDqMkyZCaQKZvVSWpFXBQVTq2kV5DBBkbPJpDJqarw9Vk698bI4D2MLse9pGI4joxMjDcb cyxssNbIWRJI1qTRmVaaIjhGz+UYMiMyjPpVVFRUtMJduCNbO/wr0VQ7e2/Z/QrMil5JS5BU AkQsNJc6BCXIRyInmhH0VBSK+OArgmuDhWI++IHgZI1DON3iLGrC+UQrgorO/UI++IxgzG4V ear8iGQ4Udwj9rA/kQpnW4q8IhjRKoC6Kpc3gRNh0P7hOe5hXyIEnrneIA/LiER4/fGxwMNC Ygm46qxe6XlEGnx+e0fI18yFh+fHvCwllsLQ15+YhzEiEAbHKgU8L4YDTWWYRxiIYjF8+zQi 4D0kw/6WDxjPfjD+oFHMcxBMTrTiPOfBlYcOnG8+hKCxvVfEJ2KgvfqMe5DErbAM6lsiebE5 MPH9qMizDIQMDhXJ+epQ6Budlp0Pl4oP/xuvhPc3B7CTKMQ2w45thgXbDAu2/2IXkLAWBbAm Tp/JcpQpeuZ1NyDvqw2La0YXe1I7ECFB5GxZ2qP8dLmI2cPt03cgkGCkv+y03poul2mYfbms 2ag25+hYrgMp3Kd9Cgual2F0/wGDRU0pomNiYuhYKk5BUWSgrH5NUrqcyGQsbDbLmljzdJ9A Ig2yotYXTVkyLmzd+HB5P1Ww88dA/NTBUBVZIL+atEi76V33rC8RvqsX9Eo35m9N5YpV2t01 sZOntpiqJ74dPWufe6IkuVL+ZMNo1do+rlI9cMSv62nKXuWqc88KG6xTub7ankd5QxrNcODy toDR9u2uxqncywdqbncb0o4X1Tz+02/vc5JCTstQYZiZY/4C/KVT8csDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprHIsWRmVeSWpSXmKPExsWy7bCSnG5acUOMweMDMhYbZ6xntTh/fgO7 xa0GGYvLu+awWXzuPcJoMeP8PiaLl0d+MFqsPXKX3eJ24wo2i7unjrI5cHnculPvsWlVJ5vH wXd7mDz6tqxi9Fix+ju7x+dNcgFsUVw2Kak5mWWpRfp2CVwZd37aFaziqZh9bB5zA+NDzi5G Tg4JAROJ821b2boYuTiEBHYzSkxvOsQIkZCUmHbxKHMXIweQLSxx+HAxSFhI4C2jxJLpliC2 sICLRH/7OXYQW0TAR2LqrjYmEJtZYD+TxI//jBAz1zJKPHsxH2wmm4CWxP4XN9hAbH4BRYmr Px6DxXkF7CQevTwD1swioCLxY3UDC4gtKhAhcffiCxaIGkGJkzOfgNmcAhoStz99B7uNWUBd Yv08IYi94hK3nsyHukFeonnrbOYJjMKzkHTPQuiYhaRjFpKOBYwsqxglUwuKc9Nziw0LjPJS y/WKE3OLS/PS9ZLzczcxgmNNS2sH44kT8YcYBTgYlXh4I07XxwixJpYVV+YeYpTgYFYS4Z2U 2xAjxJuSWFmVWpQfX1Sak1p8iFGag0VJnFc+/1ikkEB6YklqdmpqQWoRTJaJg1OqgTF8Nvta PymewPIHkV/VFMU4E6VlD4T7Vjxw8I6sY1L7Kp+jX//uboVsmuM/tYbZBQd+KX7mUfww/Wna +5OJ2dM2ivC+q8jv2aWRL3zYtWrJVD/+3RtOHzMRzE3hsJyu1M2am3Jm6T/pzZzOMzzEt9dx r9eQOXS1fJeSTmzaljlTJyty7DE9q8RSnJFoqMVcVJwIAMyAR3yxAgAA X-CMS-MailID: 20190307012702epcas1p12c8946bc55d6fb216dc29e79f8c3452a X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20190125135414eucas1p2ffc71c63f1a27f67d076dec889954b40 References: <20190125135403.10228-1-m.szyprowski@samsung.com> <20190306231014.GE7915@amd> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pavel, On 19. 3. 7. 오전 8:10, Pavel Machek wrote: > On Fri 2019-01-25 14:54:03, Marek Szyprowski wrote: >> This way devfreq core ensures that all its devices will be set to safe >> operation points before reboot operation. There are board on which some >> aggressive power saving operation points are behind the capabilities of >> the bootloader to properly reset the hardware and boot the board. This >> way one can avoid board crash early after reboot. >> >> Similar pattern is used in CPUfreq subsystem. > > This looks somehow dangerous to me. I guess this will break someone's > shutdown, and on battery-powered devices, that's quite bad thing to > do. This patch executes the devfreq_suspend() for all devfreq devices. The devfreq_suspend() does the following: 1. (mandatory) stop the polling of governor. 2. (optional) If devfreq device specifies the 'opp-suspend' property in DT, the devfreq changes the frequency by using the devfreq->suspend_freq. If the user of devfreq device doesn't want to change the frequency during the system shutdown, just don't add the 'opp-suspend' property in DT. And the devfreq_suspend() will just stop the polling for governor. Even if on battery-powered devices, I think it is not problem to stop the polling of governor during the system shutdown. In my case, I don't know what is dangerous. Could you explain it more detailed. > > Could we explicitely do it only for devices that need it? > Pavel > > -- Best Regards, Chanwoo Choi Samsung Electronics