linux-kernel - Re: [PATCH v2] cpufreq: intel_pstate: Add additional OOB enabling bit

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Date:   Tue, 23 Jun 2020 18:35:48 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     lenb@...nel.org, viresh.kumar@...aro.org, dsmythies@...us.net,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cpufreq: intel_pstate: Add additional OOB enabling bit

On Friday, June 12, 2020 8:09:57 PM CEST Srinivas Pandruvada wrote:
> Add additional bit for OOB (Out of band) enabling of P-states. In this
> case intel_pstate shouldn't load. Currently, only "BIT(8) == 1" of the
> MSR MSR_MISC_PWR_MGMT is considered as OOB. Also add "BIT(18) == 1" as
> OOB condition.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
> v2
>    - As suggested by Doug add OOB in debug message
>    - Atleast added local definition of OOB mask
> 
>  drivers/cpufreq/intel_pstate.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index 8e23a698ce04..4e9bfd2509b8 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -2677,6 +2677,7 @@ static struct acpi_platform_list plat_info[] __initdata = {
>  	{ } /* End */
>  };
>  
> +#define BITMASK_OOB	(BIT(8) | BIT(18))
>  static bool __init intel_pstate_platform_pwr_mgmt_exists(void)
>  {
>  	const struct x86_cpu_id *id;
> @@ -2686,8 +2687,9 @@ static bool __init intel_pstate_platform_pwr_mgmt_exists(void)
>  	id = x86_match_cpu(intel_pstate_cpu_oob_ids);
>  	if (id) {
>  		rdmsrl(MSR_MISC_PWR_MGMT, misc_pwr);
> -		if (misc_pwr & (1 << 8)) {
> -			pr_debug("Bit 8 in the MISC_PWR_MGMT MSR set\n");
> +		if (misc_pwr & BITMASK_OOB) {
> +			pr_debug("Bit 8 or 18 in the MISC_PWR_MGMT MSR set\n");
> +			pr_debug("P states are controlled in Out of Band mode by the firmware/hardware\n");
>  			return true;
>  		}
>  	}
> 

Applied as 5.8-rc material with some edits in the subject/changelog, thanks!