Re: [PATCH -next] arm64: Export __cpu_logical_map

From: Sumit Gupta
Date: Sun Jul 26 2020 - 07:47:08 EST

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.

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.