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

[Adrian Huang <adrian.huang@hp.com>]

Re-send my reply email because my gmail account sent the email with html format. 
It was rejected by vger kernel. My bad.

BTW, the patch was verified correctly on HP ProLiant servers. Also, please see my other answers below. 

-- Adrian

於 四，2013-10-31 於 23:47 +0100，Rafael J. Wysocki 提到：
> On Thursday, October 31, 2013 03:23:24 PM Dirk Brandewie wrote:
> > On 10/31/2013 03:29 PM, Rafael J. Wysocki wrote:
> > > 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?
> > 
> > As long as you are comfortable with the ACPI related logic for matching
> > the entry in the hw_vendor_info vendor_info[] I have no objections.
> 
> Well, is there any other way to address that?

I put hw_vendor_info vendor_info in case other vendors (Dell, Lenovo...)
have their firmware power management. Vendors should make sure their
firmware power management works properly, and they can go for adding
their vendor info to the variable.

> > One question though can this be disabled via the HP BIOS if the
> > customer does not want to use the firmware power management?
> 
> Good question.  Adrian?

Yes. HP BIOS has several power management modes (firmware, OS-control
and so on). For the OS control mode in HP BIOS, the Intel p-state driver
will be loaded. When the customer chooses the firmware power management
in HP BIOS, the Intel p-state driver will be ignored.

> 
> 
> > >> ---
> > >> 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;
> > >>
> > 
> > --
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