Re: [PATCH 1/3] intel_pstate: skip the driver if Sun server has ACPI _PPC method

From: ethan zhao
Date: Thu Nov 20 2014 - 19:37:28 EST


On 2014/11/21 0:50, Dirk Brandewie wrote:
On 11/19/2014 12:22 PM, Linda Knippers wrote:
On 11/18/2014 3:37 AM, Ethan Zhao wrote:
Oracle Sun X86 servers have dynamic power capping capability that works via
ACPI _PPC method etc, so skip loading this driver if Sun server has ACPI _PPC

Signed-off-by: Ethan Zhao <ethan.zhao@xxxxxxxxxx>
drivers/cpufreq/intel_pstate.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 27bb6d3..5498eb0 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -943,6 +943,21 @@ static bool intel_pstate_no_acpi_pss(void)
return true;

+static bool intel_pstate_has_acpi_ppc(void)
+ int i;
+ for_each_possible_cpu(i) {
+ struct acpi_processor *pr = per_cpu(processors, i);
+ if (!pr)
+ continue;
+ if (acpi_has_method(pr->handle, "_PPC"))
+ return true;
+ }
+ return false;
struct hw_vendor_info {
u16 valid;
char oem_id[ACPI_OEM_ID_SIZE];
@@ -952,6 +967,7 @@ struct hw_vendor_info {
/* Hardware vendor-specific info that has its own power management modes */
static struct hw_vendor_info vendor_info[] = {
{1, "HP ", "ProLiant"},
+ {1, "ORACLE", ""},
{0, "", ""},

@@ -969,12 +985,16 @@ static bool intel_pstate_platform_pwr_mgmt_exists(void)
!strncmp(hdr.oem_table_id, v_info->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
return true;
+ if (!strncmp(hdr.oem_id, v_info->oem_id, ACPI_OEM_ID_SIZE) &&
+ intel_pstate_has_acpi_ppc())

We need try this on a few platforms to make sure this patch doesn't break the
HP platforms that may or may not need this driver, depending on the BIOS settings.

It looks like HP systems would get swept up in this check too if they have _PPC
No , this patch checks the oem_id against 'ORACLE" first, will not affect other vendors
even they have _PPC.

What about extending the hw_vendor_info struct to include whether _PSS or
Except refer to ACPI DSDT, I don't know how to fill such info.
_PPC should be done for the platform since it appears that oracle and HP
have implemented similar functionality using two different methods.
Maybe Linda could answer this whether HP also has _PPC and should be wept out.
But that doesn't happen with on the same box at the same time.


I don't suppose you tested on a ProLiant too?

-- ljk

+ return true;

return false;
#else /* CONFIG_ACPI not enabled */
static inline bool intel_pstate_platform_pwr_mgmt_exists(void) { return false; }
+static inline bool intel_pstate_has_acpi_ppc(void) { return false; }
#endif /* CONFIG_ACPI */

static int __init intel_pstate_init(void)

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