From: Sudeep Holla <sudeep.holla@arm.com>
To: Sumit Gupta <sumitg@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mikko Perttunen <mperttunen@nvidia.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Hulk Robot <hulkci@huawei.com>,
"linux-kernel@vger.kernel.org List"
<linux-kernel@vger.kernel.org>,
linux-arm-kernel@lists.infradead.org,
Bibek Basu <bbasu@nvidia.com>,
linux-tegra <linux-tegra@vger.kernel.org>,
Thierry Reding <thierry.reding@gmail.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Jon Hunter <jonathanh@nvidia.com>
Subject: Re: [PATCH -next] arm64: Export __cpu_logical_map
Date: Mon, 10 Aug 2020 08:49:56 +0100 [thread overview]
Message-ID: <20200810074956.GB28091@bogus> (raw)
In-Reply-To: <e3a4bc21-c334-4d48-90b5-aab8d187939e@nvidia.com>
On Sat, Aug 01, 2020 at 05:46:43PM +0530, Sumit Gupta wrote:
>
> > > > > > ERROR: modpost: "__cpu_logical_map" [drivers/cpufreq/tegra194-cpufreq.ko] undefined!
> > > > > >
> > > > > > ARM64 tegra194-cpufreq driver use cpu_logical_map, export
> > > > > > __cpu_logical_map to fix build issue.
> > > > > >
> > > >
> > > > I wonder why like other instances in the drivers, the mpidr is not get
> > > > directly from the cpu. The cpufreq_driver->init call happens when the cpu
> > > > is being brought online and is executed on the required cpu IIUC.
> > > >
> > > Yes, this occurs during hotplug case.
> > > But in the case of system boot, 'cpufreq_driver->init' is called later
> > > during cpufreq platform driver's probe. The value of CPU in 'policy->cpu'
> > > can be different from the current CPU. That's why read_cpuid_mpidr() can't
> > > be used.
> > >
> >
> > Fair enough, why not do cross call like in set_target ? Since it is one-off
> > in init, I don't see any issue when you are doing it runtime for set_target.
> >
> > > > read_cpuid_mpidr() is inline and avoids having to export the logical_cpu_map.
> > > > Though we may not add physical hotplug anytime soon, less dependency
> > > > on this cpu_logical_map is better given that we can resolve this without
> > > > the need to access the map.
> > > >
> >
> > To be honest, we have tried to remove all the dependency on cluster id
> > in generic code as it is not well defined. This one is tegra specific
> > driver so should be fine. But I am still bit nervous to export
> > cpu_logical_map as we have no clue what that would mean for physical
> > hotplug.
> >
> As suggested, I have done below change to get the cluster number using
> read_cpuid_mpidr(). Please review and suggest if this looks ok?
> I will send formal patch if the change is fine.
>
> Thanks,
> Sumit
>
> ----
>
> diff --git a/drivers/cpufreq/tegra194-cpufreq.c
> b/drivers/cpufreq/tegra194-cpufreq.c
> index bae527e..06f5ccf 100644
> --- a/drivers/cpufreq/tegra194-cpufreq.c
> +++ b/drivers/cpufreq/tegra194-cpufreq.c
> @@ -56,9 +56,11 @@ struct read_counters_work {
>
> static struct workqueue_struct *read_counters_wq;
>
> -static enum cluster get_cpu_cluster(u8 cpu)
> +static void get_cpu_cluster(void *cluster)
> {
> - return MPIDR_AFFINITY_LEVEL(cpu_logical_map(cpu), 1);
> + u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
> +
> + *((uint32_t *) cluster) = MPIDR_AFFINITY_LEVEL(mpidr, 1);
> }
>
> /*
> @@ -186,8 +188,10 @@ static unsigned int tegra194_get_speed(u32 cpu)
> static int tegra194_cpufreq_init(struct cpufreq_policy *policy)
> {
> struct tegra194_cpufreq_data *data = cpufreq_get_driver_data();
> - int cl = get_cpu_cluster(policy->cpu);
> u32 cpu;
> + u32 cl;
> +
> + smp_call_function_single(policy->cpu, get_cpu_cluster, &cl, true);
Thanks for this, looks good to me. You can add:
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
--
Regards,
Sudeep
next prev parent reply other threads:[~2020-08-10 7:50 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200724030433.22287-1-wangkefeng.wang@huawei.com>
2020-07-24 3:08 ` [PATCH -next] arm64: Export __cpu_logical_map Kefeng Wang
2020-07-24 8:16 ` Anshuman Khandual
2020-07-24 9:13 ` Mark Rutland
2020-07-24 9:35 ` Catalin Marinas
2020-07-24 10:33 ` Anshuman Khandual
2020-07-24 9:16 ` Kefeng Wang
2020-07-24 9:30 ` Catalin Marinas
2020-07-24 10:36 ` Anshuman Khandual
2020-07-24 9:43 ` Christoph Hellwig
2020-07-24 13:10 ` Sudeep Holla
2020-07-25 2:00 ` Kefeng Wang
2020-07-26 11:46 ` Sumit Gupta
2020-07-27 16:05 ` Sudeep Holla
2020-08-01 12:16 ` Sumit Gupta
2020-08-10 7:49 ` Sudeep Holla [this message]
2020-08-10 10:19 ` Catalin Marinas
2020-08-10 12:11 ` Sudeep Holla
2020-08-11 19:44 ` Sumit Gupta
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