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Mon, 13 Jul 2020 21:14:54 +0900 (KST) Received: from [10.113.221.102] (unknown [10.113.221.102]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20200713121454epsmtip2fd722762b6911c3bcd485e6c73721002~hTuZciesl2603426034epsmtip2Z; Mon, 13 Jul 2020 12:14:54 +0000 (GMT) Subject: Re: [PATCH v2 2/2] PM / devfreq: Add governor flags to clarify the features To: Dmitry Osipenko , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: leonard.crestez@nxp.com, lukasz.luba@arm.com, enric.balletbo@collabora.com, hl@rock-chips.com, thierry.reding@gmail.com, jonathanh@nvidia.com, abel.vesa@nxp.com, chanwoo@kernel.org, myungjoo.ham@samsung.com, kyungmin.park@samsung.com, "linux-tegra@vger.kernel.org" From: Chanwoo Choi Organization: Samsung Electronics Message-ID: <69ae2524-22d0-2444-da13-fae199392029@samsung.com> Date: Mon, 13 Jul 2020 21:26:25 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:59.0) Gecko/20100101 Thunderbird/59.0 MIME-Version: 1.0 In-Reply-To: <746837bc-6734-3e52-453f-2b59bbca0230@gmail.com> Content-Language: en-US Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrPJsWRmVeSWpSXmKPExsWy7bCmnq59AE+8QeM5U4tll44yWky8cYXF YvXHx4wWa24fYrT4seEUs0XLrEUsFmeb3rBbrLj7kdXi8q45bBafe48wWnR+mcVmsbCphd3i duMKNoufu+axOPB5rJm3htFjx90ljB47Z91l99i0qpPNo7f5HZvHxnc7mDz+ztrP4tG3ZRWj x+dNcgGcUdk2GamJKalFCql5yfkpmXnptkrewfHO8aZmBoa6hpYW5koKeYm5qbZKLj4Bum6Z OUDXKymUJeaUAoUCEouLlfTtbIryS0tSFTLyi0tslVILUnIKLAv0ihNzi0vz0vWS83OtDA0M jEyBChOyMy4+38le8ECp4sf3TYwNjLMkuxg5OSQETCS+r7/DBGILCexglHiwIK+LkQvI/sQo cWX1bWYI5xujxNT2PawwHS/6/kF17GWUmL5PDaLoPVD3k9NgRcICYRKPmq6yg9giAgkSR/6A NHBxMAtsYpLYPucaM0iCTUBLYv+LG2wgNr+AosTVH48ZQWxeATuJvVsawAaxCKhK3O95BFYv CjT05LYWqBpBiZMzn7CA2JwCthKrf1wEq2EWEJe49WQ+E4QtL9G8dTbYCxICbzgkJq1tYoF4 wUWi4/U2RghbWOLV8S3sELaUxOd3e9kg7GqJlSePsEE0dzBKbNl/Aep/Y4n9SycDbeAA2qAp sX6XPkRYUWLn77mMEIv5JN597WEFKZEQ4JXoaBOCKFGWuPzgLhOELSmxuL2TbQKj0iwk78xC 8sIsJC/MQli2gJFlFaNYakFxbnpqsWGBKXJsb2IEp2wtyx2M099+0DvEyMTBeIhRgoNZSYQ3 WpQzXog3JbGyKrUoP76oNCe1+BCjKTCAJzJLiSbnA7NGXkm8oamRsbGxhYmhmamhoZI477+z 7PFCAumJJanZqakFqUUwfUwcnFINTALBK8uNPP3uHV8vqt9/q+X1lBbnmDs9nJ6C/L89vzP/ eha3/5Ps9ybWo/VexWc/7FZLnpfzcfLSc2y+EiV/jNee9Oy5w6uy8U2nn/utpCrBcxLN+9a6 vJpwf6nqsg5rDa+mJ+zuCwKrDwZM7vjf0CH8czv7xV3fcrdlS6aJ6qfUztQtmxez+VRw5xSJ Gosf/tcfvm7dtj07L/Npwvojj1fwPI06n3u6rnZVSZjcS/0rZyZb/zHNec2uWW5uf+blmVd5 Ky/7xvzZ7Xu74OUNlXmnJI5xxekvWzTroppxlsg2LuZC0UP+zQJXdKOlulYLTFnu3H9ScMeZ ZezXJmXqaNa48FhMsX377uPOy0WvliqxFGckGmoxFxUnAgDJth1mYgQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA02Ra0hTcRiH+Z9z3M6Gq+PW3F+NpqNRjfJSSodSCbqdpMIoIpLS4Y7Tcpvt qN2I5qXQldJV7ViaplFLMIeZ08qYWSiITV2si2hqGZiiGDqv1VyB3x74PQ/vhxdHhY2YL56k TaX1WmWyjMPH6ppl0g2R0Z6xwXc7peTDzhZAXnd0Y+ST8QFAVn22AtL5tA0ls9lyjGzP/Mkl H/WMe5BdDXc55ETeG0Dm/mI5ZFlmNpf8nPGIQ043lGDbllFVJVWAqu+pAJSF7eFSZlMuh8rL GuVQNaP1CDXPNmFUfq0JUBPmVdG8o/xwFZ2clE7rgyLj+Im2IQs3pU92xjllBgbA+hgBD4dE KPyRv4AYAR8XEo0Afut4gLgHH1hga0GNAP/LItjczLidEQDz7Y0clyMiDsP+TDvXxSuIODj/ exy4JJQwI3C4shx1F2MAVlU893BZHEIBm344FuvlRAC0OweAiwVEJHxZa1h0MEIOe6/2oy4W /71gqRhA3I4XbL0ziLmYR0TAJ07booMSa+BcSec/lsBPg6WIm6Uw61kxeg2I2CU5uyRhlyTs kuQ+wEzAh05hNGoNE5ISoqVPBzJKDZOmVQfG6zRmsPhfxbp68Nw0FmgFCA6sAOKobIUgRsyL FQpUyrPnaL0uVp+WTDNW4IdjMonAcarsuJBQK1PpkzSdQuv/rwjO8zUg/rwXN5mvt1Ydap71 6fBPU9i6vMPjVWucZYl1O4Smy5a3xCa+wHZsh0hYXbfLVC/Jm/Pdx/YUDfEhWcw7od/e9kze Wx02PXzIwX8Q160L6B7cfbvI7lsW7sipTF84ofHaXOdZmnRwy41SCsv2Tlj7YThUnmpskEy9 9gweylmpLT8iNn0RMda9NbG24K32j0pLtXpC1Rfw/VXATNdsFHZAN9mXaJBXnlQkeUs95jPi 92u/i28Y+gPpxyPiW6lif7+a6vObCo0bJy7du6ib27NesjHGSzUTpopiKFVo3M5J7F205kvh e95ORbuhddpmu5BwPGKZvMAkVRN+V4JWyzAmURmiQPWM8g8l5WK/TgMAAA== X-CMS-MailID: 20200713121454epcas1p3d472f83056de098afeeac42e0c5ad08f X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200713081944epcas1p22871b6d8a9455226e6cccd08ac0baa73 References: <20200713083113.5595-1-cw00.choi@samsung.com> <20200713083113.5595-3-cw00.choi@samsung.com> <746837bc-6734-3e52-453f-2b59bbca0230@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/13/20 7:37 PM, Dmitry Osipenko wrote: > 13.07.2020 11:31, Chanwoo Choi пишет: >> DEVFREQ supports the default governors like performance, powersave and also >> allows the devfreq driver to add their own governor like tegra30-devfreq.c >> according to their requirement. In result, some sysfs attributes are >> useful or not useful. Prior to that the user can access all sysfs attributes >> regardless of availability. >> >> So, clarify the access permission of sysfs attributes according to governor. >> When adding the devfreq governor, can specify the available attribute >> information by using DEVFREQ_GOV_ATTR_* constant variable. The user can >> read or write the sysfs attributes in accordance to the specified attributes. >> >> /* Devfreq governor flags for attributes and features */ >> [Definition for sysfs attributes] >> - DEVFREQ_GOV_ATTR_GOVERNOR >> - DEVFREQ_GOV_ATTR_AVAIL_GOVERNORS >> - DEVFREQ_GOV_ATTR_AVAIL_FREQUENCIES >> - DEVFREQ_GOV_ATTR_CUR_FREQ >> - DEVFREQ_GOV_ATTR_TARGET_FREQ >> - DEVFREQ_GOV_ATTR_MIN_FREQ >> - DEVFREQ_GOV_ATTR_MAX_FREQ >> - DEVFREQ_GOV_ATTR_TRANS_STAT >> - DEVFREQ_GOV_ATTR_POLLING_INTERVAL >> - DEVFREQ_GOV_ATTR_TIMER >> >> Also, the devfreq governor is able to have the specific flag as follows >> in order to implement the specific feature. For example, Devfreq allows >> user to change the governors on runtime via sysfs interface. >> But, if devfreq device uses 'passive' governor, don't allow user to change >> the governor. For this case, define the DEVFREQ_GOV_FLAT_IMMUTABLE >> and set it to flag of passive governor. >> >> [Definition for governor flag] >> - DEVFREQ_GOV_FLAG_IMMUTABLE >> : If immutable flag is set, governor is never changeable to other governors. >> - DEVFREQ_GOV_FLAG_IRQ_DRIVEN >> : Devfreq core won't schedule polling work for this governor if value is set. >> >> [Table of governor flag for devfreq governors] >> ------------------------------------------------------------------------------ >> | simple | perfor | power | user | passive | tegra30 >> | ondemand | mance | save | space| | >> ------------------------------------------------------------------------------ >> governor | O | O | O | O | O | O >> available_governors | O | O | O | O | O | O >> available_frequencies | O | O | O | O | O | O >> cur_freq | O | O | O | O | O | O >> target_freq | O | O | O | O | O | O >> min_freq | O | O | O | O | O | O >> max_freq | O | O | O | O | O | O >> trans_stat | O | O | O | O | O | O >> -------------------------------------------------------- >> polling_interval | O | X | X | X | X | O >> timer | O | X | X | X | X | X >> ------------------------------------------------------------------------------ >> immutable | X | X | X | X | O | O >> interrupt_driven | X(polling)| X | X | X | X | O (irq) >> ------------------------------------------------------------------------------ >> >> Signed-off-by: Chanwoo Choi >> --- > > Hello, Chanwoo! I tested this series on NVIDIA Tegra30 and everything > working fine! > > Reviewed-by: Dmitry Osipenko > Tested-by: Dmitry Osipenko > > > BTW, I'm curious what do you think about hiding the unsupported debugfs Do you mean that sysfs? > attributes per-device instead of returning the -EACCES? I considered the hiding of sysfs node too instead of -EACCES. But, For a long time, devfreq showed the sysfs interface of all devfreq devices regardless of the kind of devfreq governor. It means that devfreq keeps the ABI interface. If devfreq hides the unsupported sysfs node according to the type of governor, it will break the ABI. Although I knew that maybe performance/powersave/userspace didn't use the 'polling_interval' node, I just returned -EACCESS. Thanks for suggesting your opinion. We can discuss it more. -- Best Regards, Chanwoo Choi Samsung Electronics