[PATCH v2 07/11] x86/cpufreq: add "cpufreq=amd-cppc,active" para

[Penny Zheng <Penny.Zheng@xxxxxxx>]

From: Penny Zheng <penny.zheng@xxxxxxx>

The amd-cppc driver may support multiple working modes, passive and active.

Introduce `active` tag for users to explicitly select active mode and a new
variable `opt_cpufreq_active` to keep track of which mode is currently enabled.
Specific implementation will be introduced in the following commits.

Signed-off-by: Penny Zheng <Penny.Zheng@xxxxxxx>
---
v1 -> v2:
- Remove pointless initializer
- Move driver registration change to the next commit
---
 docs/misc/xen-command-line.pandoc    | 8 +++++++-
 xen/arch/x86/acpi/cpufreq/amd-cppc.c | 9 +++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index 78cfb8a02e..13f650270d 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -515,7 +515,7 @@ If set, force use of the performance counters for oprofile, 
rather than detectin
 available support.
 
 ### cpufreq
-> `= none | {{ <boolean> | xen } { 
[:[powersave|performance|ondemand|userspace][,[<maxfreq>]][,[<minfreq>]]] } 
[,verbose]} | dom0-kernel | hwp[:[<hdc>][,verbose]] | amd-cppc[:[verbose]]`
+> `= none | {{ <boolean> | xen } { 
[:[powersave|performance|ondemand|userspace][,[<maxfreq>]][,[<minfreq>]]] } 
[,verbose]} | dom0-kernel | hwp[:[<hdc>][,verbose]] | 
amd-cppc[:[active][,verbose]]`
 
 > Default: `xen`
 
@@ -538,6 +538,12 @@ choice of `dom0-kernel` is deprecated and not supported by 
all Dom0 kernels.
   on supported AMD hardware to provide finer grained frequency control 
mechanism.
   The default is disabled. If `amd-cppc` is selected, but hardware support
   is not available, Xen will fallback to cpufreq=xen.
+* `active` is a boolean to enable amd-cppc driver in active(autonomous) mode.
+  In this mode, users could provide a hint with energy performance preference
+  register to the hardware if they want to bias toward performance(0x0) or
+  energy efficiency(0xff), then CPPC power algorithm will calculate the runtime
+  workload and adjust the realtime cores frequency according to the power 
supply
+  and thermal, core voltage and some other hardware conditions.
 
 There is also support for `;`-separated fallback options:
 `cpufreq=hwp;xen,verbose`.  This first tries `hwp` and falls back to `xen` if
diff --git a/xen/arch/x86/acpi/cpufreq/amd-cppc.c 
b/xen/arch/x86/acpi/cpufreq/amd-cppc.c
index f14e7a6638..1742c57170 100644
--- a/xen/arch/x86/acpi/cpufreq/amd-cppc.c
+++ b/xen/arch/x86/acpi/cpufreq/amd-cppc.c
@@ -33,6 +33,8 @@
 #define amd_cppc_warn(fmt, args...)                         \
     printk(XENLOG_WARNING "AMD_CPPC: CPU%u warning: " fmt, cpu, ## args)
 
+static bool __ro_after_init opt_cpufreq_active;
+
 struct amd_cppc_drv_data
 {
     struct xen_processor_cppc *cppc_data;
@@ -80,6 +82,13 @@ static bool __init amd_cppc_handle_option(const char *s, 
const char *end)
         return true;
     }
 
+    ret = parse_boolean("active", s, end);
+    if ( ret >= 0 )
+    {
+        opt_cpufreq_active = ret;
+        return true;
+    }
+
     return false;
 }
 
-- 
2.34.1