From: Guennadi Liakhovetski <g.liakhovetski@gmx.de> To: Viresh Kumar <viresh.kumar@linaro.org> Cc: rjw@sisk.pl, Steve.Bannister@arm.com, linux@arm.linux.org.uk, linux-pm@vger.kernel.org, Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>, devicetree-discuss@lists.ozlabs.org, Liviu.Dudau@arm.com, linux-kernel@vger.kernel.org, cpufreq@vger.kernel.org, robin.randhawa@arm.com, linux-arm-kernel@lists.infradead.org, mark.hambleton@broadcom.com, linaro-kernel@lists.linaro.org, charles.garcia-tobin@arm.com Subject: Re: [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue Date: Thu, 7 Mar 2013 22:56:54 +0100 (CET) [thread overview] Message-ID: <Pine.LNX.4.64.1303072248560.20470@axis700.grange> (raw) In-Reply-To: <6cba8f153cfd4b0d3075a34a6dfe287bdec2eb06.1362676407.git.viresh.kumar@linaro.org> Hi Viresh On Fri, 8 Mar 2013, Viresh Kumar wrote: > big LITTLE is ARM's new Architecture focussing power/performance needs of modern > world. More information about big LITTLE can be found here: > > http://www.arm.com/products/processors/technologies/biglittleprocessing.php > http://lwn.net/Articles/481055/ > > In order to keep cpufreq support for all big LITTLE platforms simple/generic, > this patch tries to add a generic cpufreq driver layer for all big LITTLE > platforms. I like generic drivers :) cpufreq-cpu0 is yet another such generic (cpufreq) driver. Now, comparing the functionality of the two: [snip] > +/* Set clock frequency */ > +static int bL_cpufreq_set_target(struct cpufreq_policy *policy, > + unsigned int target_freq, unsigned int relation) > +{ > + struct cpufreq_freqs freqs; > + u32 cpu = policy->cpu, freq_tab_idx, cur_cluster; > + int ret = 0; > + > + cur_cluster = cpu_to_cluster(policy->cpu); > + > + freqs.old = bL_cpufreq_get(policy->cpu); > + > + /* Determine valid target frequency using freq_table */ > + cpufreq_frequency_table_target(policy, freq_table[cur_cluster], > + target_freq, relation, &freq_tab_idx); > + freqs.new = freq_table[cur_cluster][freq_tab_idx].frequency; > + > + freqs.cpu = policy->cpu; > + > + pr_debug("%s: cpu: %d, cluster: %d, oldfreq: %d, target freq: %d, new freq: %d\n", > + __func__, cpu, cur_cluster, freqs.old, target_freq, > + freqs.new); > + > + if (freqs.old == freqs.new) > + return 0; > + > + for_each_cpu(freqs.cpu, policy->cpus) > + cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE); > + > + ret = clk_set_rate(clk[cur_cluster], freqs.new * 1000); we see, that this driver "only" switches CPU clock frequencies. Whereas the cpufreq-cpu0 driver also manipulates a regulator (if available) directly. I understand, power-saving is also an important consideration for big.LITTLE systems. So, I presume, you plan to implement voltage switching in cpufreq notifiers? Now, my question is: is this (notifier) actually the preferred method and the cpufreq-cpu0 driver is doing it "wrongly?" Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/
WARNING: multiple messages have this Message-ID (diff)
From: g.liakhovetski@gmx.de (Guennadi Liakhovetski) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue Date: Thu, 7 Mar 2013 22:56:54 +0100 (CET) [thread overview] Message-ID: <Pine.LNX.4.64.1303072248560.20470@axis700.grange> (raw) In-Reply-To: <6cba8f153cfd4b0d3075a34a6dfe287bdec2eb06.1362676407.git.viresh.kumar@linaro.org> Hi Viresh On Fri, 8 Mar 2013, Viresh Kumar wrote: > big LITTLE is ARM's new Architecture focussing power/performance needs of modern > world. More information about big LITTLE can be found here: > > http://www.arm.com/products/processors/technologies/biglittleprocessing.php > http://lwn.net/Articles/481055/ > > In order to keep cpufreq support for all big LITTLE platforms simple/generic, > this patch tries to add a generic cpufreq driver layer for all big LITTLE > platforms. I like generic drivers :) cpufreq-cpu0 is yet another such generic (cpufreq) driver. Now, comparing the functionality of the two: [snip] > +/* Set clock frequency */ > +static int bL_cpufreq_set_target(struct cpufreq_policy *policy, > + unsigned int target_freq, unsigned int relation) > +{ > + struct cpufreq_freqs freqs; > + u32 cpu = policy->cpu, freq_tab_idx, cur_cluster; > + int ret = 0; > + > + cur_cluster = cpu_to_cluster(policy->cpu); > + > + freqs.old = bL_cpufreq_get(policy->cpu); > + > + /* Determine valid target frequency using freq_table */ > + cpufreq_frequency_table_target(policy, freq_table[cur_cluster], > + target_freq, relation, &freq_tab_idx); > + freqs.new = freq_table[cur_cluster][freq_tab_idx].frequency; > + > + freqs.cpu = policy->cpu; > + > + pr_debug("%s: cpu: %d, cluster: %d, oldfreq: %d, target freq: %d, new freq: %d\n", > + __func__, cpu, cur_cluster, freqs.old, target_freq, > + freqs.new); > + > + if (freqs.old == freqs.new) > + return 0; > + > + for_each_cpu(freqs.cpu, policy->cpus) > + cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE); > + > + ret = clk_set_rate(clk[cur_cluster], freqs.new * 1000); we see, that this driver "only" switches CPU clock frequencies. Whereas the cpufreq-cpu0 driver also manipulates a regulator (if available) directly. I understand, power-saving is also an important consideration for big.LITTLE systems. So, I presume, you plan to implement voltage switching in cpufreq notifiers? Now, my question is: is this (notifier) actually the preferred method and the cpufreq-cpu0 driver is doing it "wrongly?" Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/
next prev parent reply other threads:[~2013-03-07 21:57 UTC|newest] Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-03-07 17:14 [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue Viresh Kumar 2013-03-07 17:14 ` Viresh Kumar 2013-03-07 21:56 ` Guennadi Liakhovetski [this message] 2013-03-07 21:56 ` Guennadi Liakhovetski 2013-03-08 4:20 ` Viresh Kumar 2013-03-08 4:20 ` Viresh Kumar 2013-03-08 6:11 ` Guennadi Liakhovetski 2013-03-08 6:11 ` Guennadi Liakhovetski 2013-03-09 3:06 ` Viresh Kumar 2013-03-09 3:06 ` Viresh Kumar 2013-03-10 15:58 ` Francesco Lavra 2013-03-10 15:58 ` Francesco Lavra 2013-03-11 0:57 ` Viresh Kumar 2013-03-11 0:57 ` Viresh Kumar 2013-03-11 0:57 ` Viresh Kumar 2013-03-21 23:50 ` Rafael J. Wysocki 2013-03-21 23:50 ` Rafael J. Wysocki 2013-03-22 2:21 ` Viresh Kumar 2013-03-22 2:21 ` Viresh Kumar 2013-03-26 9:51 Viresh Kumar 2013-03-26 9:51 ` Viresh Kumar 2013-03-26 13:17 ` Rob Herring 2013-03-26 13:17 ` Rob Herring 2013-03-26 14:30 ` Viresh Kumar 2013-03-26 14:30 ` Viresh Kumar 2013-04-13 20:13 ` Francesco Lavra 2013-04-13 20:13 ` Francesco Lavra 2013-04-15 7:02 ` Viresh Kumar 2013-04-15 7:02 ` Viresh Kumar
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=Pine.LNX.4.64.1303072248560.20470@axis700.grange \ --to=g.liakhovetski@gmx.de \ --cc=Liviu.Dudau@arm.com \ --cc=Steve.Bannister@arm.com \ --cc=charles.garcia-tobin@arm.com \ --cc=cpufreq@vger.kernel.org \ --cc=devicetree-discuss@lists.ozlabs.org \ --cc=linaro-kernel@lists.linaro.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-pm@vger.kernel.org \ --cc=linux@arm.linux.org.uk \ --cc=mark.hambleton@broadcom.com \ --cc=rjw@sisk.pl \ --cc=robin.randhawa@arm.com \ --cc=sudeep.karkadanagesha@arm.com \ --cc=viresh.kumar@linaro.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.