Re: [PATCH v3] cpufreq: intel_pstate: skip the driver if ACPI has power mgmt option

Rafael J. Wysocki
2013-10-31T22:17:03Z

On Thursday, October 31, 2013 11:24:05 PM Adrian Huang wrote:
> Do not load the Intel pstate driver if the platform firmware
> (ACPI BIOS) supports the power management alternatives.
> The ACPI BIOS indicates that the OS control mode can be used
> if the _PSS (Performance Supported States) is defined in ACPI
> table. For the OS control mode, the Intel pstate driver will be
> loaded.
>
> Signed-off-by: Adrian Huang <adrian.huang@hp.com>

Do I assume correctly that this has been tested on the affected hardware?

Dirk, any objections?

> ---
> Changes from v2:
> - Remove unnecessary assignments and parentheses (Thanks to Rafael)
>
> Changes from v1:
> - Minimize indentation levels (Thanks to Rafael)
> - Re-define some local variables (Thanks to by Rafael)
> - Return -ENODEV if platform FW has power management modes (Thanks to by Dirk)
>
> drivers/cpufreq/intel_pstate.c | 70 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 70 insertions(+)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index eb3fdc7..9ec1d6c 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -26,6 +26,8 @@
> #include <linux/fs.h>
> #include <linux/debugfs.h>
> #include <trace/events/power.h>
> +#include <linux/acpi.h>
> +#include <acpi/processor.h>
>
> #include <asm/div64.h>
> #include <asm/msr.h>
> @@ -129,6 +131,18 @@ static struct perf_limits limits = {
> .max_sysfs_pct = 100,
> };
>
> +struct hw_vendor_info {
> + u16 valid;
> + char oem_id[ACPI_OEM_ID_SIZE];
> + char oem_table_id[ACPI_OEM_TABLE_ID_SIZE];
> +};
> +
> +/* Hardware vendor-specific info that has its own power management modes */
> +static struct hw_vendor_info vendor_info[] = {
> + {1, "HP ", "ProLiant"},
> + {0, "", ""},
> +};
> +
> static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
> int deadband, int integral) {
> pid->setpoint = setpoint;
> @@ -698,6 +712,55 @@ static int intel_pstate_msrs_not_valid(void)
>
> return 0;
> }
> +
> +static bool intel_pstate_no_acpi_pss(void)
> +{
> + int i;
> +
> + for_each_possible_cpu(i) {
> + acpi_status status;
> + union acpi_object *pss;
> + struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> + struct acpi_processor *pr = per_cpu(processors, i);
> +
> + if (!pr)
> + continue;
> +
> + status = acpi_evaluate_object(pr->handle, "_PSS",
> + NULL, &buffer);
> + if (ACPI_FAILURE(status))
> + continue;
> +
> + pss = buffer.pointer;
> + if (pss && pss->type == ACPI_TYPE_PACKAGE) {
> + kfree(pss);
> + return false;
> + }
> +
> + kfree(pss);
> + }
> +
> + return true;
> +}
> +
> +static bool intel_pstate_platform_pwr_mgmt_exists(void)
> +{
> + struct acpi_table_header hdr;
> + struct hw_vendor_info *v_info;
> +
> + if (ACPI_FAILURE(acpi_get_table_header(ACPI_SIG_FADT, 0, &hdr)))
> + return false;
> +
> + for (v_info = vendor_info; v_info->valid; v_info++) {
> + if (!strncmp(hdr.oem_id, v_info->oem_id, ACPI_OEM_ID_SIZE)
> + && !strncmp(hdr.oem_table_id, v_info->oem_table_id, ACPI_OEM_TABLE_ID_SIZE)
> + && intel_pstate_no_acpi_pss())
> + return true;
> + }
> +
> + return false;
> +}
> +
> static int __init intel_pstate_init(void)
> {
> int cpu, rc = 0;
> @@ -706,6 +769,13 @@ static int __init intel_pstate_init(void)
> if (no_load)
> return -ENODEV;
>
> + /*
> + * The Intel pstate driver will be ignored if the platform
> + * firmware has its own power management modes.
> + */
> + if (!acpi_disabled && intel_pstate_platform_pwr_mgmt_exists())
> + return -ENODEV;
> +
> id = x86_match_cpu(intel_pstate_cpu_ids);
> if (!id)
> return -ENODEV;
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.