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Mon, 28 Jan 2019 11:57:26 +0000 (GMT) Subject: Re: [PATCH] devfreq: Suspend all devices on system shutdown To: myungjoo.ham@samsung.com, "linux-kernel@vger.kernel.org" , "linux-pm@vger.kernel.org" , "linux-samsung-soc@vger.kernel.org" Cc: Chanwoo Choi , Krzysztof Kozlowski , Bartlomiej Zolnierkiewicz , Lukasz Luba , Markus Reichl From: Marek Szyprowski Message-ID: Date: Mon, 28 Jan 2019 12:57:25 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190128080535epcms1p44636143629448c4e24a6628e87a72bf2@epcms1p4> Content-Transfer-Encoding: 7bit Content-Language: en-US X-Brightmail-Tracker: H4sIAAAAAAAAA02Se0hTcRTH++1ud3fTxfVqeTIrmJSp5FwYXEisYH+MHhL0R1ADm3lRyReb WiaUYmkt0wgf83ZLU2Yy87XMdIXg1IYIU9M0THsusocauKBEMq9Xy/8+33O+h/M9cAiMapME EEmpGYwhVZ+sxOXi9ue/XXuCZ2N0Efk2Fd1qbpbQ457PEnpwsEVKT+QG0iN2Dqfnb/Yi2jzY JaK/9P5C9Ou8evygTDsxeVlrs17Htd2zz0Ta4jYr0s7bth+XnJJHxTPJSVmMQRV9Rp6Y+9CF 0m1eF0buBOWi+zITkhFARsKUvVZsQnKCIusRlDY0rAoPgkWLAwliHkFN3TC2NnKjqhATGg8Q 1L0cWh2ZQ/CtuFbKu3xJDZQUuqR8w498j+CnixPxAiOnEIw5LCLehZNqMM2YcJ4VZDRUDExK eBaTO8E617PMBLGJ1MHVEblg8YH+SreYZxkZAyw3i3jGyB3wZIbDBPaHCXfVyi4gu6TQOFK5 mlsDzYWfkMC+8NXZJhU4EJY61wbyERSaWakgihA85jpwwbUfepzDK4kwMgSa7SqhfAiKWvpw vgzkRng14yOE2Ai32yswoayAawWU4N4FrLPp39ruoRfYLaRk153GrjuHXXcO+39vNRJbkT+T aUxJYIx7U5nz4UZ9ijEzNSH8bFqKDS3/0sAfp6cD2RfjHIgkkNJb0bJ0TEdJ9FnG7BQHAgJT +inKxmN0lCJen32RMaTFGjKTGaMDbSXESn9FzoZ3pykyQZ/BnGOYdMaw1hURsoBcVHR3lG6l TzaeCApemnvkKdIdDhOpo1RD3tJ9ORYuuv4ItbnfvuVA/Gj5U/WkalRTXRNJTcdycREK92jB lZyjXB4XnWf5EBrGaqJmvnf6UiXl7WnuHwvT+Qh3X6qg25raa81vchbeljaMed1T7w4f3iYb c4T0JX/0MGVWV7BSbEzUq0Mxg1H/F4oSv/JHAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrKIsWRmVeSWpSXmKPExsVy+t/xe7pq7/xiDHpWaFpsnLGe1eL6l+es FufPb2C3uNUgY3F51xw2i8+9RxgtZpzfx2Tx8sgPRovbjSvYHDg9bt2p99i0qpPN4+C7PUwe fVtWMXp83iQXwBqlZ1OUX1qSqpCRX1xiqxRtaGGkZ2hpoWdkYqlnaGwea2VkqqRvZ5OSmpNZ llqkb5egl9Gw5hxjwSbuisuzlRsYF3J2MXJySAiYSHTPb2cGsYUEljJKnL8qDhGXkTg5rYEV whaW+HOti62LkQuo5i2jxLqna9hAEsICLhL97efYQWwRgYeMEoc2aIAUMQvcBxo0+RALRMdJ Roltna/AOtgEDCW63naB2bwCdhLTT98BW8EioCqx6v1hMFtUIEZi1pM+dogaQYmTM5+wgNic An4Ss+a8YwSxmQXUJf7Mu8QMYctLbH87B8oWl7j1ZD7TBEahWUjaZyFpmYWkZRaSlgWMLKsY RVJLi3PTc4uN9IoTc4tL89L1kvNzNzECo3DbsZ9bdjB2vQs+xCjAwajEw7vhv2+MEGtiWXFl 7iFGCQ5mJRHeqdf9YoR4UxIrq1KL8uOLSnNSiw8xmgI9N5FZSjQ5H5gg8kriDU0NzS0sDc2N zY3NLJTEec8bVEYJCaQnlqRmp6YWpBbB9DFxcEo1MF4NX3/T5Tl/+ITdiuYnX67nSODPf7wj 5Tuvb9TBrpj7dgvVtc7oODUu1X/VM3fC+soYBcPjJf+W6zyWd7rneufOtBdLfX7t23s9aXJm Ve+pzyx7+4546bgfcC+auy/4s5Ysv+CLHA3N/YLh/icD2n7OuWbZyz+xQ7y18NOEV7NrDiVs 0/95ba8SS3FGoqEWc1FxIgCJj/DT2AIAAA== X-CMS-MailID: 20190128115726eucas1p1c1ea64fc7dd4bcde6e4c3c5acf0a77d6 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20190125135414eucas1p2ffc71c63f1a27f67d076dec889954b40 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20190125135414eucas1p2ffc71c63f1a27f67d076dec889954b40 References: <20190125135403.10228-1-m.szyprowski@samsung.com> <20190128080535epcms1p44636143629448c4e24a6628e87a72bf2@epcms1p4> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi MyungJoo, On 2019-01-28 09:05, MyungJoo Ham 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. >> >> Reported-by: Markus Reichl >> Signed-off-by: Marek Szyprowski >> --- > You are invoking ALL devfreq suspend callbacks at shutdown > with this commit. > > Can you make it invoke only devices explicitly saying their needs > to handle "SHUTDOWN" event? > > For example, we can add a flag at struct devfreq_dev_profile: > "uint32_t requirement" > , where > 0x1: need to operate at the initial frequency for suspend > 0x2: need to operate at the initial frequency for shutdown > 0x4: it forgets its status at resume, reconfigure frequency at resume. > (or reverse 0x1's semantics for the backward compatibility) Frankly speaking this looks like an over-engineering. Switching to safe frequency during reboot shouldn't have any negative side-effects. IMHO such flags can be always added later, once there will be a real use case for them. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland