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cpufreq: Register drivers only after CPU devices have been registered 

[ Upstream commit 46770be0cf ]

The cpufreq core heavily depends on the availability of the struct
device for CPUs and if they aren't available at the time cpufreq driver
is registered, we will never succeed in making cpufreq work.

This happens due to following sequence of events:

- cpufreq_register_driver()
  - subsys_interface_register()
  - return 0; //successful registration of driver

... at a later point of time

- register_cpu();
  - device_register();
    - bus_probe_device();
      - sif->add_dev();
	- cpufreq_add_dev();
	  - get_cpu_device(); //FAILS
  - per_cpu(cpu_sys_devices, num) = &cpu->dev; //used by get_cpu_device()
  - return 0; //CPU registered successfully

Because the per-cpu variable cpu_sys_devices is set only after the CPU
device is regsitered, cpufreq will never be able to get it when
cpufreq_add_dev() is called.

This patch avoids this failure by making sure device structure of at
least CPU0 is available when the cpufreq driver is registered, else
return -EPROBE_DEFER.

Reported-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Co-developed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Viresh Kumar 2019-11-14 09:06:17 +05:30 committed by Greg Kroah-Hartman
parent c17480cb33
commit 32e1ac30b6
1 changed files with 7 additions and 0 deletions
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7
drivers/cpufreq/cpufreq.c
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@ -2634,6 +2634,13 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
if (cpufreq_disabled())
return -ENODEV;
/*
* The cpufreq core depends heavily on the availability of device
* structure, make sure they are available before proceeding further.
*/
if (!get_cpu_device(0))
return -EPROBE_DEFER;
if (!driver_data || !driver_data->verify || !driver_data->init ||
!(driver_data->setpolicy || driver_data->target_index ||
driver_data->target) ||