linux-kernel - Re: [PATCH 4/4] cpufreq/amd-pstate: Remove the redundant amd_pstate_set

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Message-ID: <5cfc19d6-e171-4049-ad00-5f8474051c9b@gmail.com>
Date: Sat, 26 Oct 2024 23:27:13 -0500
From: Mario Limonciello <superm1@...il.com>
To: Klara Modin <klarasmodin@...il.com>,
 Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>, gautham.shenoy@....com,
 mario.limonciello@....com, perry.yuan@....com, rafael@...nel.org,
 viresh.kumar@...aro.org
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, klara@...m.eu
Subject: Re: [PATCH 4/4] cpufreq/amd-pstate: Remove the redundant
 amd_pstate_set_driver() call



On 10/26/24 06:58, Klara Modin wrote:
> Hi,
> 
> On 2024-10-17 12:05, Dhananjay Ugwekar wrote:
>> amd_pstate_set_driver() is called twice, once in amd_pstate_init() and 
>> once
>> as part of amd_pstate_register_driver(). Move around code and eliminate
>> the redundancy.
>>
>> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 12 ++++--------
>>   1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 13ee5cac901d..6f6d961879cc 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -1848,9 +1848,11 @@ static int __init amd_pstate_init(void)
>>           return -ENODEV;
>>       }
>> -    ret = amd_pstate_set_driver(cppc_state);
>> -    if (ret)
>> +    ret = amd_pstate_register_driver(cppc_state);
>> +    if (ret) {
>> +        pr_err("failed to register with return %d\n", ret);
>>           return ret;
>> +    }
>>       /* capability check */
>>       if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
>> @@ -1870,12 +1872,6 @@ static int __init amd_pstate_init(void)
>>               return ret;
>>       }
>> -    ret = amd_pstate_register_driver(cppc_state);
>> -    if (ret) {
>> -        pr_err("failed to register with return %d\n", ret);
>> -        return ret;
>> -    }
>> -
>>       dev_root = bus_get_dev_root(&cpu_subsys);
>>       if (dev_root) {
>>           ret = sysfs_create_group(&dev_root->kobj, 
>> &amd_pstate_global_attr_group);
> 
> 
> This seems to break boot on my Zen 2 desktop (my Zen 4 laptop is fine, 
> however). I don't see any messages on the console and nothing shows up 
> in the pstore either.
> 
> I'll attach the kernel log from a normal boot (with the patch reverted) 
> in case it helps.
> 
> Please let me know if there's anything else you need.
> 
> Regards,
> Klara Modin

Hi,

Thanks for reporting.  I think this might be a regression on shared 
memory designs specifically because static calls weren't updated yet.

Can you try this below diff?

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 206725219d8c9..2f0e29b05963d 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1857,12 +1857,6 @@ static int __init amd_pstate_init(void)
                 return -ENODEV;
         }

-       ret = amd_pstate_register_driver(cppc_state);
-       if (ret) {
-               pr_err("failed to register with return %d\n", ret);
-               return ret;
-       }
-
         /* capability check */
         if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
                 pr_debug("AMD CPPC MSR based functionality is 
supported\n");
@@ -1881,6 +1875,12 @@ static int __init amd_pstate_init(void)
                         return ret;
         }

+       ret = amd_pstate_register_driver(cppc_state);
+       if (ret) {
+               pr_err("failed to register with return %d\n", ret);
+               return ret;
+       }
+
         dev_root = bus_get_dev_root(&cpu_subsys);
         if (dev_root) {
                 ret = sysfs_create_group(&dev_root->kobj, 
&amd_pstate_global_attr_group);