Re: [PATCH 2/4] cpufreq/amd-pstate: Do not attempt to clear MSR_AMD_CPPC_ENABLE

["Gautham R. Shenoy" <gautham.shenoy@amd.com>]

On Wed, Oct 23, 2024 at 10:21:08AM +0000, Dhananjay Ugwekar wrote:
> MSR_AMD_CPPC_ENABLE is a write once register, i.e. attempting to clear
> it is futile, it will not take effect. Hence, return if disable (0)
> argument is passed to the msr_cppc_enable()
> 
> Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>


> ---
>  drivers/cpufreq/amd-pstate.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 0b4a4d69c14d..576251e61ce0 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -311,6 +311,12 @@ static inline int msr_cppc_enable(bool enable)
>  	int ret, cpu;
>  	unsigned long logical_proc_id_mask = 0;
>  
> +       /*
> +        * MSR_AMD_CPPC_ENABLE is write-once, once set it cannot be cleared.
> +        */
> +	if (!enable)
> +		return 0;
> +
>  	if (enable == cppc_enabled)
>  		return 0;
>  
> -- 
> 2.34.1
>