Re: [PATCH v10 6/8] cpufreq: amd-pstate: get transition delay and latency value from ACPI tables

Huang Rui
2024-04-15T15:02:05Z

On Mon, Mar 25, 2024 at 11:03:26AM +0800, Yuan, Perry wrote:
> Make pstate driver initially retrieve the P-state transition delay and
> latency values from the BIOS ACPI tables which has more reasonable
> delay and latency values according to the platform design and
> requirements.
>
> Previously there values were hardcoded at specific value which may
> have conflicted with platform and it might not reflect the most
> accurate or optimized setting for the processor.
>
> [054h 0084 8] Preserve Mask : FFFFFFFF00000000
> [05Ch 0092 8] Write Mask : 0000000000000001
> [064h 0100 4] Command Latency : 00000FA0
> [068h 0104 4] Maximum Access Rate : 0000EA60
> [06Ch 0108 2] Minimum Turnaround Time : 0000
>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> Tested-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
> Signed-off-by: Perry Yuan <perry.yuan@amd.com>

Acked-by: Huang Rui <ray.huang@amd.com>

> ---
> drivers/cpufreq/amd-pstate.c | 34 ++++++++++++++++++++++++++++++++--
> 1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 6708c436e1a2..ec049b62b366 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -756,6 +756,36 @@ static void amd_pstate_update_limits(unsigned int cpu)
> mutex_unlock(&amd_pstate_driver_lock);
> }
>
> +/**
> + * Get pstate transition delay time from ACPI tables that firmware set
> + * instead of using hardcode value directly.
> + */
> +static u32 amd_pstate_get_transition_delay_us(unsigned int cpu)
> +{
> + u32 transition_delay_ns;
> +
> + transition_delay_ns = cppc_get_transition_latency(cpu);
> + if (transition_delay_ns == CPUFREQ_ETERNAL)
> + return AMD_PSTATE_TRANSITION_DELAY;
> +
> + return transition_delay_ns / NSEC_PER_USEC;
> +}
> +
> +/**
> + * Get pstate transition latency value from ACPI tables that firmware
> + * set instead of using hardcode value directly.
> + */
> +static u32 amd_pstate_get_transition_latency(unsigned int cpu)
> +{
> + u32 transition_latency;
> +
> + transition_latency = cppc_get_transition_latency(cpu);
> + if (transition_latency == CPUFREQ_ETERNAL)
> + return AMD_PSTATE_TRANSITION_LATENCY;
> +
> + return transition_latency;
> +}
> +
> /**
> * amd_pstate_init_freq: Initialize the max_freq, min_freq,
> * nominal_freq and lowest_nonlinear_freq for
> @@ -848,8 +878,8 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> goto free_cpudata1;
> }
>
> - policy->cpuinfo.transition_latency = AMD_PSTATE_TRANSITION_LATENCY;
> - policy->transition_delay_us = AMD_PSTATE_TRANSITION_DELAY;
> + policy->cpuinfo.transition_latency = amd_pstate_get_transition_latency(policy->cpu);
> + policy->transition_delay_us = amd_pstate_get_transition_delay_us(policy->cpu);
>
> policy->min = min_freq;
> policy->max = max_freq;
> --
> 2.34.1
>