From: Viresh Kumar <viresh.kumar@linaro.org>
To: sumitg <sumitg@nvidia.com>
Cc: rjw@rjwysocki.net, catalin.marinas@arm.com, will@kernel.org,
thierry.reding@gmail.com, jonathanh@nvidia.com, talho@nvidia.com,
linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, bbasu@nvidia.com,
mperttunen@nvidia.com
Subject: Re: [TEGRA194_CPUFREQ Patch 2/3] cpufreq: Add Tegra194 cpufreq driver
Date: Wed, 8 Apr 2020 11:23:01 +0530 [thread overview]
Message-ID: <20200408055301.jhvu5bc2luu3b5qr@vireshk-i7> (raw)
In-Reply-To: <3ab4136c-8cca-c2f9-d286-b82dac23e720@nvidia.com>
On 07-04-20, 23:48, sumitg wrote:
> On 06/04/20 8:25 AM, Viresh Kumar wrote:
> > On 05-04-20, 00:08, sumitg wrote:
> > > On 26/03/20 5:20 PM, Viresh Kumar wrote:
> > > > On 03-12-19, 23:02, Sumit Gupta wrote:
> > > > > diff --git a/drivers/cpufreq/tegra194-cpufreq.c b/drivers/cpufreq/tegra194-cpufreq.c
> > > > > +static unsigned int tegra194_get_speed_common(u32 cpu, u32 delay)
> > > > > +{
> > > > > + struct read_counters_work read_counters_work;
> > > > > + struct tegra_cpu_ctr c;
> > > > > + u32 delta_refcnt;
> > > > > + u32 delta_ccnt;
> > > > > + u32 rate_mhz;
> > > > > +
> > > > > + read_counters_work.c.cpu = cpu;
> > > > > + read_counters_work.c.delay = delay;
> > > > > + INIT_WORK_ONSTACK(&read_counters_work.work, tegra_read_counters);
> > > > > + queue_work_on(cpu, read_counters_wq, &read_counters_work.work);
> > > > > + flush_work(&read_counters_work.work);
> > > >
> > > > Why can't this be done in current context ?
> > > >
> > > We used work queue instead of smp_call_function_single() to have long delay.
> >
> > Please explain completely, you have raised more questions than you
> > answered :)
> >
> > Why do you want to have long delays ?
> >
> Long delay value is used to have the observation window long enough for
> correctly reconstructing the CPU frequency considering noise.
> In next patch version, changed delay value to 500us which in our tests is
> considered reliable.
I understand that you need to put a udelay() while reading the freq from
hardware, that is fine, but why do you need a workqueue for that? Why can't you
just read the values directly from the same context ?
--
viresh
next prev parent reply other threads:[~2020-04-08 5:53 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-03 17:32 [TEGRA194_CPUFREQ Patch 1/3] firmware: tegra: adding function to get BPMP data Sumit Gupta
2019-12-03 17:32 ` [TEGRA194_CPUFREQ Patch 2/3] cpufreq: Add Tegra194 cpufreq driver Sumit Gupta
2019-12-04 5:40 ` Viresh Kumar
2019-12-04 10:55 ` sumitg
2019-12-04 11:27 ` Viresh Kumar
2019-12-04 13:57 ` Dmitry Osipenko
2019-12-05 2:51 ` Viresh Kumar
2019-12-05 12:55 ` Dmitry Osipenko
2020-03-25 23:59 ` sumitg
2019-12-04 13:59 ` Dmitry Osipenko
2019-12-05 14:15 ` Dmitry Osipenko
2020-03-26 11:50 ` Viresh Kumar
2020-04-04 18:38 ` sumitg
2020-04-06 2:55 ` Viresh Kumar
2020-04-07 18:18 ` sumitg
2020-04-08 5:53 ` Viresh Kumar [this message]
2020-04-08 11:24 ` sumitg
2020-04-09 7:44 ` Viresh Kumar
2020-04-09 11:21 ` Sumit Gupta
2020-04-13 6:21 ` Viresh Kumar
2020-04-13 12:20 ` Sumit Gupta
2020-04-14 5:45 ` Viresh Kumar
2020-04-15 11:25 ` Sumit Gupta
2020-04-16 3:37 ` Viresh Kumar
2020-04-16 7:06 ` Sumit Gupta
2019-12-03 17:32 ` [TEGRA194_CPUFREQ Patch 3/3] arm64: defconfig: Enable CONFIG_ARM_TEGRA194_CPUFREQ Sumit Gupta
2019-12-03 17:42 ` [TEGRA194_CPUFREQ Patch 1/3] firmware: tegra: adding function to get BPMP data Thierry Reding
2019-12-04 8:45 ` Mikko Perttunen
2019-12-04 9:17 ` Viresh Kumar
2019-12-04 9:33 ` Thierry Reding
2019-12-04 9:51 ` Viresh Kumar
2020-04-07 10:05 ` Thierry Reding
2020-04-27 7:18 ` Thierry Reding
2020-04-29 8:21 ` Sumit Gupta
2020-05-06 16:58 ` Thierry Reding
2020-05-20 14:43 ` Rob Herring
2020-05-20 15:38 ` Thierry Reding
2020-05-20 16:21 ` Rob Herring
2019-12-04 10:21 ` Mikko Perttunen
2019-12-04 10:26 ` Viresh Kumar
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