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Subject[PATCH 2/3] cpufreq: amd-pstate: Allow replacing existing cpufreq drivers when loaded
Date
`amd-pstate` can be compiled as a module.  This however can be a
deficiency because `acpi-cpufreq` will be loaded earlier when compiled
into the kernel meaning `amd-pstate` doesn't get a chance.
`acpi-cpufreq` is also unable to be unloaded in this circumstance.

To better improve the usability of `amd-pstate` when compiled as a module,
add an optional module parameter that will force it to replace other
cpufreq drivers at startup.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
drivers/cpufreq/amd-pstate.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 9ce75ed11f8e..31a04e818195 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -63,6 +63,11 @@ module_param(shared_mem, bool, 0444);
MODULE_PARM_DESC(shared_mem,
"enable amd-pstate on processors with shared memory solution (false = disabled (default), true = enabled)");

+static bool replace = false;
+module_param(replace, bool, 0444);
+MODULE_PARM_DESC(replace,
+ "replace other cpufreq drivers upon init if necessary");
+
static struct cpufreq_driver amd_pstate_driver;

/**
@@ -598,9 +603,11 @@ static int __init amd_pstate_init(void)
return -ENODEV;
}

- /* don't keep reloading if cpufreq_driver exists */
- if (cpufreq_get_current_driver())
- return -EEXIST;
+ if (cpufreq_get_current_driver()) {
+ ret = replace ? cpufreq_unregister_driver(NULL) : -EEXIST;
+ if (ret)
+ return ret;
+ }

/* capability check */
if (boot_cpu_has(X86_FEATURE_CPPC)) {
--
2.34.1
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