From: Sibi Sankar <email@example.com> To: firstname.lastname@example.org Cc: Kyungmin Park <email@example.com>, Chanwoo Choi <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v4] PM / devfreq: Restart previous governor if new governor fails to start Date: Wed, 06 Mar 2019 23:14:09 +0530 Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <20190305071808epcms1p89cd924ae1c7fc344b7e554f5f18592d2@epcms1p8> On 2019-03-05 12:48, MyungJoo Ham wrote: >> Hey MyungJoo, Kyungmin >> Did you get a chance to think about how you >> want this fix implemented? >> >> On 2019-02-19 10:42, Sibi Sankar wrote: >>> Hey MyungJoo, >>> >>> On 12/14/18 7:15 AM, MyungJoo Ham wrote: >>>>> From: Saravana Kannan <email@example.com> >>>>> >>>>> If the new governor fails to start, switch back to old governor so >>>>> that the >>>>> devfreq state is not left in some weird limbo. >>>>> >>>>> Signed-off-by: Sibi Sankar <firstname.lastname@example.org> >>>>> Signed-off-by: Saravana Kannan <email@example.com> >>>>> Reviewed-by: Chanwoo Choi <firstname.lastname@example.org> >>>> >>>> Hello, >>>> >>>> In overall, the idea and the implementation looks good. >>>> >>>> However, I have a question: >>>> >>>> What if the following line fails? >>>> >>>> + df->governor->event_handler(df, DEVFREQ_GOV_START, >>>> + NULL); >>>> >>>> Don't we still need something to handle for such events? >>> >>> The original discussion went as follows: >>> governor_store is expected to be used only on cases >>> where devfreq_add_device() succeeded i.e prev->governor >>> is expected to be present and DEVFREQ_GOV_START is >>> expected to succeed. Hence falling back to the previous >>> governor seems like a sensible idea. >>> >>> This would also prevent DEVFREQ_GOV_STOP from being called >>> on a governor were DEVFREQ_GOV_START had failed which is >>> ideal. >>> >>> That being said DEVFREQ_GOV_START can still fail for the >>> prev-governor due to some change in state of the system. >>> Do you want to handle this case by clearing the state of >>> governor rather than switching to previous governor? >>> > > If moving back to previous governor fails after > failing for "next" governor, we may assume it's fatal > and stop the device; we can simply return errors. > > In such a case, df->governor may need to be NULL as well. Thanks. Will make the necessary changes in the next re-spin. > > > Cheers, > MyungJoo -- -- Sibi Sankar -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
prev parent reply index Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-12-12 13:53 Sibi Sankar [not found] ` <CGME20181212135338epcas5p12f7a8cd1c7aab5d5c936cbc5c33eee07@epcms1p6> 2018-12-14 1:45 ` MyungJoo Ham 2019-02-19 5:12 ` Sibi Sankar 2019-03-04 8:21 ` Sibi Sankar [not found] ` <CGME20181212135338epcas5p12f7a8cd1c7aab5d5c936cbc5c33eee07@epcms1p8> 2019-03-05 7:18 ` MyungJoo Ham 2019-03-06 17:44 ` Sibi Sankar [this message]
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