From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH] PM / OPP: Allow inactive opp_device to be present in dev list Date: Tue, 29 Nov 2016 09:25:31 +0530 Message-ID: <20161129035531.GC3288@vireshk-i7> References: <2fe61813c867c173ddfcb0b9cabc00a65997a935.1480056714.git.viresh.kumar@linaro.org> <20161129024647.GY6095@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pg0-f42.google.com ([74.125.83.42]:36237 "EHLO mail-pg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753231AbcK2Dzf (ORCPT ); Mon, 28 Nov 2016 22:55:35 -0500 Received: by mail-pg0-f42.google.com with SMTP id f188so64126161pgc.3 for ; Mon, 28 Nov 2016 19:55:34 -0800 (PST) Content-Disposition: inline In-Reply-To: <20161129024647.GY6095@codeaurora.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Stephen Boyd Cc: Rafael Wysocki , jy0922.shim@samsung.com, Viresh Kumar , Nishanth Menon , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org On 28-11-16, 18:46, Stephen Boyd wrote: > That's a lot of lines for something that we want to backport to > stable kernels! Hmm, I agree. > The whole dev_list design seems fairly broken to me. Another > solution would be to iterate the cpumask in reverse, but there > doesn't seem to be a construct for that and adding one is > probably not worth the effort. > > Adding yet another member to the structure and doing accounting > in different places seems to be papering over the problem as > well. Now we want to have "inactive" devices in the list? That > seems like a problem for cpufreq to solve. It can decide to not > call OPP APIs when the cpu device isn't actually physically > removed if it wants to. > > It also exposes the OPP API's strong reliance on struct device > for everything. Really we shouldn't be storing device pointers in > the OPP core at all because we're not treating them like the > reference counted objects they are. The dev_list should go > probably go away and be replaced with some sort of counter. It > would also be nice if struct device had a pointer to the OPP > table(s) for a device so the lookup is direct. If the struct device gets a pointer to the opp-table, then yes we can kill the dev-list completely. I will work on cleaning up OPP core a bit later on. > BTW, _dev_pm_opp_remove_table() calls _find_opp_dev() twice, once > to find the opp_table for a device and then to find the > opp_device inside the table that was used to match up the table > in the first place. Madness! > > Anyway, rant over, how about handing out the opp table pointer to > the caller so they can pass it back in when they call the put > side? That should fix the same problem if I understand correctly. Yes, that can be a solution for the time being. > We should think about changing the API further so that callers > have to "get" the OPP table cookie for their device and then pass > that pointer to the dev_pm_*_set() APIs instead of passing a > struct device pointer. That would save lots of cycles searching > for something we already had. Hmm, we need to do some cleanup soon I believe. Also note that we want to kill the RCU thing :) > -static inline void dev_pm_opp_put_regulator(struct device *dev) {} > +static inline void dev_pm_opp_put_regulator(struct opp_table *opp_table) {} We need to modify few more things as well. I will send a patch for that soon. -- viresh