Re: [PATCH v2] cpufreq: intel_pstate: skip the driver if ACPI has power mgmt option

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Thursday, October 31, 2013 03:29:59 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) object 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>
> ---
> Changes since v1:
>  * Minimize indentation levels (Commented by Rafael)
>  * Re-define some local variables (Commented by Rafael)
>  * Return -ENODEV if platform FW has power management modes (Commented by Dirk)
> 
>  drivers/cpufreq/intel_pstate.c | 70 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)

Minor nits ->

> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index eb3fdc7..8770d67 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 = AE_OK;
> +		struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +		struct acpi_processor *pr = per_cpu(processors, i);
> +		union acpi_object *pss = NULL;

status and pss don't need to be initialized above.

> +
> +		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)) {

The condition can be written as (pss && pss->type == ACPI_TYPE_PACKAGE)

> +			kfree(buffer.pointer);

and you can do kfree(pss) instead here (and below).

> +			return false;
> +		}
> +
> +		kfree(buffer.pointer);
> +	}
> +
> +	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.