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To: Sylwester Nawrocki , Lukasz Luba , Krzysztof Kozlowski , Willy Wolff Cc: MyungJoo Ham , Kyungmin Park , Kukjin Kim , linux-pm@vger.kernel.org, "linux-samsung-soc@vger.kernel.org" , linux-arm-kernel@lists.infradead.org, "linux-kernel@vger.kernel.org" From: Chanwoo Choi Organization: Samsung Electronics Message-ID: Date: Mon, 29 Jun 2020 10:52:17 +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: Content-Language: en-US Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrMJsWRmVeSWpSXmKPExsWy7bCmru5Gt59xBlMu2Fj0P37NbHH+/AZ2 i7NNb9gtNj2+xmpxedccNovPvUcYLWac38dksbCphd3iduMKNovDb9pZLb6deMTowO2xZt4a Ro+ds+6ye2xa1cnmsXlJvUffllWMHp83yQWwRWXbZKQmpqQWKaTmJeenZOal2yp5B8c7x5ua GRjqGlpamCsp5CXmptoqufgE6Lpl5gCdp6RQlphTChQKSCwuVtK3synKLy1JVcjILy6xVUot SMkpsCzQK07MLS7NS9dLzs+1MjQwMDIFKkzIzpjw7SBrQatAxaIJS5gaGD/wdDFyckgImEjM nNnE3sXIxSEksINRYsrs+UwQzidGiRt3rrFAOJ8ZJZq/7GKEaTm+/y1UYhejxLGtE6D63zNK LLlxkhmkSljATmL+tV2sIAkRgRWMEm9OLWIEcZgFjjJJ7Go6xgJSxSagJbH/xQ02EJtfQFHi 6o/HYDt4gbq3POlmBbFZBFQlLnYtBZsqKhAmcXJbC1SNoMTJmU/A5nAK2EvMbN0JVsMsIC5x 6wnIFyC2vMT2t3OYQRZLCBzhkPh28BELxBMuEnNaGqAeEpZ4dXwLO4QtJfGyvw3KrpZYefII G0RzB6PElv0XWCESxhL7l04G2sABtEFTYv0ufYiwosTO33MZIRbzSbz72sMKUiIhwCvR0SYE UaIscfnBXSYIW1JicXsn2wRGpVlI3pmF5IVZSF6YhbBsASPLKkax1ILi3PTUYsMCY+QI38QI Tr1a5jsYp739oHeIkYmD8RCjBAezkgjvZ+tvcUK8KYmVValF+fFFpTmpxYcYTYEBPJFZSjQ5 H5j880riDU2NjI2NLUwMzUwNDZXEeX2tLsQJCaQnlqRmp6YWpBbB9DFxcEo1MBVfyV/Pqh2m ZqI52zIucfu6CZrmln17l3tPFG3UmtbpHtTUMLGF4VRc5tcn/xOMGt91/4pM8voWNvVWxb5r i4U/210847vgbo/ohS8XChY9v/Y/vKglLeY/70LBmh9Wbx9rT0u/F7N0hcA1+86EjpZ8N4Zj Mp/nW3vc/XtbxuHVwuOxctmXFrFy89xU2cR6sGC/T+bD03bLb/KbN7JlPGFuf/+muWKadtQ/ 78bgLce+97Vut9ZUFHtzsjsvwUrjoMeyH48N9mpVNV9+eko+edbhpB9O/4IkX32YduWw+os7 O+54eb+qnsPw7tT0W8EGZusOfy5piv9xd/0Zg3n8aSnz5Ao23NqXv4glw7l9z3clluKMREMt 5qLiRADlueccRgQAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprLIsWRmVeSWpSXmKPExsWy7bCSnO5Gt59xBtd/8Fn0P37NbHH+/AZ2 i7NNb9gtNj2+xmpxedccNovPvUcYLWac38dksbCphd3iduMKNovDb9pZLb6deMTowO2xZt4a Ro+ds+6ye2xa1cnmsXlJvUffllWMHp83yQWwRXHZpKTmZJalFunbJXBlTPh2kLWgVaBi0YQl TA2MH3i6GDk5JARMJI7vf8vSxcjFISSwg1Hi9PJn7BAJSYlpF48ydzFyANnCEocPF0PUvGWU mND9hwmkRljATmL+tV2sIAkRgRWMErc2/gZzmAWOM0msfb+BGaLlAZPE1nV7wVrYBLQk9r+4 wQZi8wsoSlz98ZgRxOYFGrXlSTcriM0ioCpxsWspM4gtKhAmsXPJYyaIGkGJkzOfsIDYnAL2 EjNbd4LVMAuoS/yZdwnKFpe49WQ+E4QtL7H97RzmCYzCs5C0z0LSMgtJyywkLQsYWVYxSqYW FOem5xYbFhjlpZbrFSfmFpfmpesl5+duYgTHoJbWDsY9qz7oHWJk4mA8xCjBwawkwvvZ+luc EG9KYmVValF+fFFpTmrxIUZpDhYlcd6vsxbGCQmkJ5akZqemFqQWwWSZODilGpjs9ZW2PJ0j JDCh9ZYj44KQm3ZcJ3pjveb82B8nahx+cIlBo6DQIsW7OzmUdoduYFR+lVaTyXeozHLnhXnz 5VI43n5NWv52bePh9U8+6e4zu8UTnPlS9PrfT3HOHcrNuu/zrA1emi9bNTdq+eS3S/fcjNCX PXKQ6ey5GUtus11Lu8X9V1lip+EqflPjsDaLxYZZsmb997K8Pvz9ldw97ciOoJs9DAmWfq7C ueV8rhcbt/zc+FNuw8qq2SdvLdsRHys6MZh3BU995t9cuYbmI745Nw5MWH9giY7kCQbWRqt3 5c/37zsfuGDJ0XWsRlr5S+6fXMdSbexr9S+GK6si53CpnPKS4y5yN+LD4/aHXPyoxFKckWio xVxUnAgAV5adLjADAAA= X-CMS-MailID: 20200629014105epcas1p4250936a7acd173c58c1b9d46ea80ca42 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: 20200624103308eucas1p188a5fe3cee1916d9430c9971c2dab3a3 References: <20200623164733.qbhua7b6cg2umafj@macmini.local> <20200623191129.GA4171@kozik-lap> <85f5a8c0-7d48-f2cd-3385-c56d662f2c88@arm.com> Sender: linux-samsung-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org Hi Sylwester, On 6/25/20 12:11 AM, Sylwester Nawrocki wrote: > Hi All, > > On 24.06.2020 12:32, Lukasz Luba wrote: >> I had issues with devfreq governor which wasn't called by devfreq >> workqueue. The old DELAYED vs DEFERRED work discussions and my patches >> for it [1]. If the CPU which scheduled the next work went idle, the >> devfreq workqueue will not be kicked and devfreq governor won't check >> DMC status and will not decide to decrease the frequency based on low >> busy_time. >> The same applies for going up with the frequency. They both are >> done by the governor but the workqueue must be scheduled periodically. > > As I have been working on resolving the video mixer IOMMU fault issue > described here: https://patchwork.kernel.org/patch/10861757 > I did some investigation of the devfreq operation, mostly on Odroid U3. > > My conclusions are similar to what Lukasz says above. I would like to add > that broken scheduling of the performance counters read and the devfreq > updates seems to have one more serious implication. In each call, which > normally should happen periodically with fixed interval we stop the counters, > read counter values and start the counters again. But if period between > calls becomes long enough to let any of the counters overflow, we will > get wrong performance measurement results. My observations are that > the workqueue job can be suspended for several seconds and conditions for > the counter overflow occur sooner or later, depending among others > on the CPUs load. > Wrong bus load measurement can lead to setting too low interconnect bus > clock frequency and then bad things happen in peripheral devices. > > I agree the workqueue issue needs to be fixed. I have some WIP code to use > the performance counters overflow interrupts instead of SW polling and with It is good way to resolve the overflow issue. > that the interconnect bus clock control seems to work much better. > -- Best Regards, Chanwoo Choi Samsung Electronics