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3b7cbd308e
During cpufreq driver's registration, if the ->init() callback for all
the CPUs fail then there is not much point in keeping the driver around
as it will only account for more of unnecessary noise, for example
cpufreq core will try to suspend/resume the driver which never got
registered properly.
The removal of such a driver is avoided if the driver carries the
CPUFREQ_STICKY flag. This was added way back [1] in 2004 and perhaps no
one should ever need it now. A lot of drivers do set this flag, probably
because they just copied it from other drivers.
This was added earlier for some platforms [2] because their cpufreq
drivers were getting registered before the CPUs were registered with
subsys framework. And hence they used to fail.
The same isn't true anymore though. The current code flow in the kernel
is:
start_kernel()
-> kernel_init()
-> kernel_init_freeable()
-> do_basic_setup()
-> driver_init()
-> cpu_dev_init()
-> subsys_system_register() //For CPUs
-> do_initcalls()
-> cpufreq_register_driver()
Clearly, the CPUs will always get registered with subsys framework
before any cpufreq driver can get probed. Remove the flag and update the
relevant drivers.
Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/include/linux/cpufreq.h?id=7cc9f0d9a1ab04cedc60d64fd8dcf7df224a3b4d # [1]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/arch/arm/mach-sa1100/cpu-sa1100.c?id=f59d3bbe35f6268d729f51be82af8325d62f20f5 # [2]
Change-Id: If2509516ec7fa7518750e23e0198614654dbf9b7
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Samuel Pascua <pascua.samuel.14@gmail.com>
Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>
80 lines
1.9 KiB
C
80 lines
1.9 KiB
C
/*
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* clock scaling for the UniCore-II
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*
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* Code specific to PKUnity SoC and UniCore ISA
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*
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* Maintained by GUAN Xue-tao <gxt@mprc.pku.edu.cn>
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* Copyright (C) 2001-2010 Guan Xuetao
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/err.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/init.h>
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#include <linux/clk.h>
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#include <linux/cpufreq.h>
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#include <mach/hardware.h>
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static struct cpufreq_driver ucv2_driver;
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/* make sure that only the "userspace" governor is run
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* -- anything else wouldn't make sense on this platform, anyway.
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*/
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static int ucv2_verify_speed(struct cpufreq_policy *policy)
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{
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if (policy->cpu)
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return -EINVAL;
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cpufreq_verify_within_cpu_limits(policy);
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return 0;
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}
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static int ucv2_target(struct cpufreq_policy *policy,
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unsigned int target_freq,
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unsigned int relation)
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{
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struct cpufreq_freqs freqs;
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int ret;
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freqs.old = policy->cur;
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freqs.new = target_freq;
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cpufreq_freq_transition_begin(policy, &freqs);
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ret = clk_set_rate(policy->clk, target_freq * 1000);
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cpufreq_freq_transition_end(policy, &freqs, ret);
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return ret;
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}
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static int __init ucv2_cpu_init(struct cpufreq_policy *policy)
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{
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if (policy->cpu != 0)
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return -EINVAL;
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policy->min = policy->cpuinfo.min_freq = 250000;
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policy->max = policy->cpuinfo.max_freq = 1000000;
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policy->clk = clk_get(NULL, "MAIN_CLK");
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return PTR_ERR_OR_ZERO(policy->clk);
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}
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static struct cpufreq_driver ucv2_driver = {
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.flags = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
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.verify = ucv2_verify_speed,
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.target = ucv2_target,
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.get = cpufreq_generic_get,
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.init = ucv2_cpu_init,
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.name = "UniCore-II",
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};
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static int __init ucv2_cpufreq_init(void)
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{
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return cpufreq_register_driver(&ucv2_driver);
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}
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arch_initcall(ucv2_cpufreq_init);
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