Re: [PATCH 6.3.y] cpufreq: amd-pstate: Add ->fast_switch() callback

[Wyes Karny <wyes.karny@amd.com>]

On 30 May 11:16, Wyes Karny wrote:
> From: "Gautham R. Shenoy" <gautham.shenoy@amd.com>
> 
> [ Upstream commit 3bf8c6307bad5c0cc09cde982e146d847859b651 ]
> 
> Schedutil normally calls the adjust_perf callback for drivers with
> adjust_perf callback available and fast_switch_possible flag set.
> However, when frequency invariance is disabled and schedutil tries to
> invoke fast_switch. So, there is a chance of kernel crash if this
> function pointer is not set. To protect against this scenario add
> fast_switch callback to amd_pstate driver.
> 
> Fixes: 1d215f0319c2 ("cpufreq: amd-pstate: Add fast switch function for AMD P-State")
> Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
> Signed-off-by: Wyes Karny <wyes.karny@amd.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> (cherry picked from commit 4badf2eb1e986bdbf34dd2f5d4c979553a86fe54)
> ---
>  drivers/cpufreq/amd-pstate.c | 37 +++++++++++++++++++++++++++++-------
>  1 file changed, 30 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 8dd46fad151e..7cce90d16b8d 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -422,9 +422,8 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy)
>  	return 0;
>  }
>  
> -static int amd_pstate_target(struct cpufreq_policy *policy,
> -			     unsigned int target_freq,
> -			     unsigned int relation)
> +static int amd_pstate_update_freq(struct cpufreq_policy *policy,
> +				  unsigned int target_freq, bool fast_switch)
>  {
>  	struct cpufreq_freqs freqs;
>  	struct amd_cpudata *cpudata = policy->driver_data;
> @@ -443,14 +442,36 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
>  	des_perf = DIV_ROUND_CLOSEST(target_freq * cap_perf,
>  				     cpudata->max_freq);
>  
> -	cpufreq_freq_transition_begin(policy, &freqs);
> -	amd_pstate_update(cpudata, min_perf, des_perf,
> -			  max_perf, false);
> -	cpufreq_freq_transition_end(policy, &freqs, false);
> +	WARN_ON(fast_switch && !policy->fast_switch_enabled);
> +	/*
> +	 * If fast_switch is desired, then there aren't any registered
> +	 * transition notifiers. See comment for
> +	 * cpufreq_enable_fast_switch().
> +	 */
> +	if (!fast_switch)
> +		cpufreq_freq_transition_begin(policy, &freqs);
> +
> +	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, fast_switch);
> +
> +	if (!fast_switch)
> +		cpufreq_freq_transition_end(policy, &freqs, false);
>  
>  	return 0;
>  }
>  
> +static int amd_pstate_target(struct cpufreq_policy *policy,
> +			     unsigned int target_freq,
> +			     unsigned int relation)
> +{
> +	return amd_pstate_update_freq(policy, target_freq, false);
> +}
> +
> +static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy,
> +				  unsigned int target_freq)
> +{
> +	return amd_pstate_update_freq(policy, target_freq, true);
> +}
> +
>  static void amd_pstate_adjust_perf(unsigned int cpu,
>  				   unsigned long _min_perf,
>  				   unsigned long target_perf,
> @@ -692,6 +713,7 @@ static int amd_pstate_cpu_exit(struct cpufreq_policy *policy)
>  
>  	freq_qos_remove_request(&cpudata->req[1]);
>  	freq_qos_remove_request(&cpudata->req[0]);
> +	policy->fast_switch_possible = false;
>  	kfree(cpudata);
>  
>  	return 0;
> @@ -1226,6 +1248,7 @@ static struct cpufreq_driver amd_pstate_driver = {
>  	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
>  	.verify		= amd_pstate_verify,
>  	.target		= amd_pstate_target,
> +	.fast_switch    = amd_pstate_fast_switch,
>  	.init		= amd_pstate_cpu_init,
>  	.exit		= amd_pstate_cpu_exit,
>  	.suspend	= amd_pstate_cpu_suspend,

Please ignore this. Wrong patch.
Sorry for inconvenience.

Thanks,
Wyes

> -- 
> 2.34.1
>