cpufreq: amd-pstate: avoid uninitialized variable use

The new epp support causes warnings about three separate
but related bugs:

1) failing before allocation should just return an error:

drivers/cpufreq/amd-pstate.c:951:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (!dev)
            ^~~~
drivers/cpufreq/amd-pstate.c:1018:9: note: uninitialized use occurs here
        return ret;
               ^~~

2) wrong variable to store return code:

drivers/cpufreq/amd-pstate.c:963:6: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (rc)
            ^~
drivers/cpufreq/amd-pstate.c:1019:9: note: uninitialized use occurs here
        return ret;
               ^~~
drivers/cpufreq/amd-pstate.c:963:2: note: remove the 'if' if its condition is always false
        if (rc)
        ^~~~~~~

3) calling amd_pstate_set_epp() in cleanup path after determining
that it should not be called:

drivers/cpufreq/amd-pstate.c:1055:6: error: variable 'epp' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
        if (cpudata->epp_policy == cpudata->policy)
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/cpufreq/amd-pstate.c:1080:30: note: uninitialized use occurs here
        amd_pstate_set_epp(cpudata, epp);
                                    ^~~

All three are trivial to fix, but most likely there are additional bugs
in this function when the error handling was not really tested.

Fixes: ffa5096a7c33 ("cpufreq: amd-pstate: implement Pstate EPP support for the AMD processors")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Wyes Karny <wyes.karny@amd.com>
Reviewed-by: Yuan Perry <Perry.Yuan@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 70debd5a9f402b43c4abcbdafd6834a79320446f..b8862afef4e4018996a72c10793915d94c7701af 100644 (file)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -940,7 +940,6 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
        int min_freq, max_freq, nominal_freq, lowest_nonlinear_freq, ret;
        struct amd_cpudata *cpudata;
        struct device *dev;
-       int rc;
        u64 value;
 
        /*
@@ -950,7 +949,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
        amd_perf_ctl_reset(policy->cpu);
        dev = get_cpu_device(policy->cpu);
        if (!dev)
-               goto free_cpudata1;
+               return -ENODEV;
 
        cpudata = kzalloc(sizeof(*cpudata), GFP_KERNEL);
        if (!cpudata)
@@ -959,8 +958,8 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
        cpudata->cpu = policy->cpu;
        cpudata->epp_policy = 0;
 
-       rc = amd_pstate_init_perf(cpudata);
-       if (rc)
+       ret = amd_pstate_init_perf(cpudata);
+       if (ret)
                goto free_cpudata1;
 
        min_freq = amd_get_min_freq(cpudata);
@@ -1076,9 +1075,9 @@ static void amd_pstate_epp_init(unsigned int cpu)
                value |= (u64)epp << 24;
        }
 
+       amd_pstate_set_epp(cpudata, epp);
 skip_epp:
        WRITE_ONCE(cpudata->cppc_req_cached, value);
-       amd_pstate_set_epp(cpudata, epp);
        cpufreq_cpu_put(policy);
 }