linux-kernel - Re: [PATCH 04/15] cpufreq/amd-pstate: Use FIELD_PREP and FIELD

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Message-ID: <Z1KXz3N1bIfI1pmd@BLRRASHENOY1.amd.com>
Date: Fri, 6 Dec 2024 11:51:03 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Perry Yuan <perry.yuan@....com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Dhananjay Ugwekar <Dhananjay.Ugwekar@....com>
Subject: Re: [PATCH 04/15] cpufreq/amd-pstate: Use FIELD_PREP and FIELD_GET
 macros

On Thu, Dec 05, 2024 at 04:28:36PM -0600, Mario Limonciello wrote:
> The FIELD_PREP and FIELD_GET macros improve readability and help
> to avoid shifting bugs.

Indeed.

The code looks better with this.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>
--
Thanks and Regards
gautham.

> 
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/cpufreq/amd-pstate.c | 45 ++++++++++++++++--------------------
>  1 file changed, 20 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 22e212ca514c5..dbe014f3c2beb 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -22,6 +22,7 @@
>  
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> +#include <linux/bitfield.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -88,6 +89,11 @@ static bool cppc_enabled;
>  static bool amd_pstate_prefcore = true;
>  static struct quirk_entry *quirks;
>  
> +#define AMD_PSTATE_MAX_PERF_MASK		GENMASK(7, 0)
> +#define AMD_PSTATE_MIN_PERF_MASK		GENMASK(15, 8)
> +#define AMD_PSTATE_DES_PERF_MASK		GENMASK(23, 16)
> +#define AMD_PSTATE_EPP_PERF_MASK		GENMASK(31, 24)
> +
>  /*
>   * AMD Energy Preference Performance (EPP)
>   * The EPP is used in the CCLK DPM controller to drive
> @@ -182,7 +188,6 @@ static DEFINE_MUTEX(amd_pstate_driver_lock);
>  
>  static s16 msr_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
>  {
> -	u64 epp;
>  	int ret;
>  
>  	if (!cppc_req_cached) {
> @@ -192,9 +197,8 @@ static s16 msr_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
>  			return ret;
>  		}
>  	}
> -	epp = (cppc_req_cached >> 24) & 0xFF;
>  
> -	return (s16)epp;
> +	return FIELD_GET(AMD_PSTATE_EPP_PERF_MASK, cppc_req_cached);
>  }
>  
>  DEFINE_STATIC_CALL(amd_pstate_get_epp, msr_get_epp);
> @@ -269,12 +273,11 @@ static inline void amd_pstate_update_perf(struct amd_cpudata *cpudata,
>  
>  static int msr_set_epp(struct amd_cpudata *cpudata, u32 epp)
>  {
> -	int ret;
> -
>  	u64 value = READ_ONCE(cpudata->cppc_req_cached);
> +	int ret;
>  
> -	value &= ~GENMASK_ULL(31, 24);
> -	value |= (u64)epp << 24;
> +	value &= ~AMD_PSTATE_EPP_PERF_MASK;
> +	value |= FIELD_PREP(AMD_PSTATE_EPP_PERF_MASK, epp);
>  	WRITE_ONCE(cpudata->cppc_req_cached, value);
>  
>  	ret = wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> @@ -533,18 +536,15 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
>  		des_perf = 0;
>  	}
>  
> -	value &= ~AMD_CPPC_MIN_PERF(~0L);
> -	value |= AMD_CPPC_MIN_PERF(min_perf);
> -
> -	value &= ~AMD_CPPC_DES_PERF(~0L);
> -	value |= AMD_CPPC_DES_PERF(des_perf);
> -
>  	/* limit the max perf when core performance boost feature is disabled */
>  	if (!cpudata->boost_supported)
>  		max_perf = min_t(unsigned long, nominal_perf, max_perf);
>  
> -	value &= ~AMD_CPPC_MAX_PERF(~0L);
> -	value |= AMD_CPPC_MAX_PERF(max_perf);
> +	value &= ~(AMD_PSTATE_MAX_PERF_MASK | AMD_PSTATE_MIN_PERF_MASK |
> +		   AMD_PSTATE_DES_PERF_MASK);
> +	value |= FIELD_PREP(AMD_PSTATE_MAX_PERF_MASK, max_perf);
> +	value |= FIELD_PREP(AMD_PSTATE_DES_PERF_MASK, des_perf);
> +	value |= FIELD_PREP(AMD_PSTATE_MIN_PERF_MASK, min_perf);
>  
>  	if (trace_amd_pstate_perf_enabled() && amd_pstate_sample(cpudata)) {
>  		trace_amd_pstate_perf(min_perf, des_perf, max_perf, cpudata->freq,
> @@ -1571,16 +1571,11 @@ static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
>  	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
>  		min_perf = min(cpudata->nominal_perf, max_perf);
>  
> -	/* Initial min/max values for CPPC Performance Controls Register */
> -	value &= ~AMD_CPPC_MIN_PERF(~0L);
> -	value |= AMD_CPPC_MIN_PERF(min_perf);
> -
> -	value &= ~AMD_CPPC_MAX_PERF(~0L);
> -	value |= AMD_CPPC_MAX_PERF(max_perf);
> -
> -	/* CPPC EPP feature require to set zero to the desire perf bit */
> -	value &= ~AMD_CPPC_DES_PERF(~0L);
> -	value |= AMD_CPPC_DES_PERF(0);
> +	value &= ~(AMD_PSTATE_MAX_PERF_MASK | AMD_PSTATE_MIN_PERF_MASK |
> +		   AMD_PSTATE_DES_PERF_MASK);
> +	value |= FIELD_PREP(AMD_PSTATE_MAX_PERF_MASK, max_perf);
> +	value |= FIELD_PREP(AMD_PSTATE_DES_PERF_MASK, 0);
> +	value |= FIELD_PREP(AMD_PSTATE_MIN_PERF_MASK, min_perf);
>  
>  	/* Get BIOS pre-defined epp value */
>  	epp = amd_pstate_get_epp(cpudata, value);
> -- 
> 2.43.0
>