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>,
Sudeep Holla <sudeep.holla@arm.com>,
"linux-kernel@vger.kernel.org List"
<linux-kernel@vger.kernel.org>,
Mikko Perttunen <mperttunen@nvidia.com>,
Hulk Robot <hulkci@huawei.com>, Bibek Basu <bbasu@nvidia.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH -next] arm64: Export __cpu_logical_map
Date: Mon, 27 Jul 2020 17:05:15 +0100 [thread overview]
Message-ID: <20200727160515.GA8003@bogus> (raw)
In-Reply-To: <00cf6e67-16ed-872d-2c16-0ceea6b6f514@nvidia.com>
On Sun, Jul 26, 2020 at 05:16:27PM +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.
--
Regards,
Sudeep
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next prev parent reply other threads:[~2020-07-27 16:07 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 [this message]
2020-08-01 12:16 ` Sumit Gupta
2020-08-10 7:49 ` Sudeep Holla
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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