On Tue, 2022-12-27 at 20:51 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> When _PPC returns 0, it means that the CPU frequency is not limited
> by
> the platform firmware, so make acpi_processor_get_platform_limit()
> update the frequency QoS request used by it to "no limit" in that
> case
> and avoid updating the QoS request when the _PPC return value has not
> changed.
>
> This addresses a problem with limiting CPU frequency artificially on
> some systems after CPU offline/online to the frequency that
> corresponds
> to the first entry in the _PSS return package.
>
> While at it, move the _PPC return value check against the state count
> earlier to avoid setting performance_platform_limit to an invalid
> value.
>
> Reported-by: Pratyush Yadav <ptyadav@xxxxxxxxx>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> drivers/acpi/processor_perflib.c | 27 +++++++++++++++++++++------
> 1 file changed, 21 insertions(+), 6 deletions(-)
>
> Index: linux-pm/drivers/acpi/processor_perflib.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/processor_perflib.c
> +++ linux-pm/drivers/acpi/processor_perflib.c
> @@ -53,6 +53,8 @@ static int acpi_processor_get_platform_l
> {
> acpi_status status = 0;
> unsigned long long ppc = 0;
> + s32 qos_value;
> + int index;
> int ret;
>
> if (!pr)
> @@ -72,17 +74,30 @@ static int acpi_processor_get_platform_l
> }
> }
>
> + index = ppc;
> +
> + if (pr->performance_platform_limit == index ||
> + ppc >= pr->performance->state_count)
> + return 0;
Do we need to re initialize pr->performance_platform_limit to 0 in
acpi_processor_unregister_performance()?
If PPC was 1 before the offline and after online the above check will
cause it to return as the pr->performance_platform_limit is not
changed. Not sure if the PM QOS state is preserved after offline and
online. This is stored in a per CPU variable, not in dynamically
allocated memory which will be reallocated during online again.
Thanks,
Srinivas
> +
> pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr-
> >id,
> - (int)ppc, ppc ? "" : "not");
> + index, index ? "is" : "is not");
>
> - pr->performance_platform_limit = (int)ppc;
> + pr->performance_platform_limit = index;
>
> - if (ppc >= pr->performance->state_count ||
> - unlikely(!freq_qos_request_active(&pr->perflib_req)))
> + if (unlikely(!freq_qos_request_active(&pr->perflib_req)))
> return 0;
>
> - ret = freq_qos_update_request(&pr->perflib_req,
> - pr->performance->states[ppc].core_frequency *
> 1000);
> + /*
> + * If _PPC returns 0, it means that all of the available
> states can be
> + * used ("no limit").
> + */
> + if (index == 0)
> + qos_value = FREQ_QOS_MAX_DEFAULT_VALUE;
> + else
> + qos_value = pr->performance-
> >states[index].core_frequency * 1000;
> +
> + ret = freq_qos_update_request(&pr->perflib_req, qos_value);
> if (ret < 0) {
> pr_warn("Failed to update perflib freq constraint:
> CPU%d (%d)\n",
> pr->id, ret);
>
>
>
