This commit includes the following modification:
- Introduce helper function cpufreq_cmdline_parse_xen and
cpufreq_cmdline_parse_hwp to tidy the different parsing path
- Add helper cpufreq_opts_contain to ignore user redundant setting,
like "cpufreq=hwp;hwp;xen"
- Doc refinement

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
---
v2 -> v3:
- new commit
---
 docs/misc/xen-command-line.pandoc |  3 +-
 xen/drivers/cpufreq/cpufreq.c     | 64 ++++++++++++++++++++++---------
 2 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 0c6225391d..a440042471 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -535,7 +535,8 @@ choice of `dom0-kernel` is deprecated and not supported by all Dom0 kernels.
   processor to autonomously force physical package components into idle state.
   The default is enabled, but the option only applies when `hwp` is enabled.
 
-There is also support for `;`-separated fallback options:
+User could use `;`-separated options to support universal options which they
+would like to try on any agnostic platform, *but* under priority order, like
 `cpufreq=hwp;xen,verbose`.  This first tries `hwp` and falls back to `xen` if
 unavailable.  Note: The `verbose` suboption is handled globally.  Setting it
 for either the primary or fallback option applies to both irrespective of where
diff --git a/xen/drivers/cpufreq/cpufreq.c b/xen/drivers/cpufreq/cpufreq.c
index 894bafebaa..cfae16c15f 100644
--- a/xen/drivers/cpufreq/cpufreq.c
+++ b/xen/drivers/cpufreq/cpufreq.c
@@ -71,6 +71,46 @@ unsigned int __initdata cpufreq_xen_cnt = 1;
 
 static int __init cpufreq_cmdline_parse(const char *s, const char *e);
 
+static bool __init cpufreq_opts_contain(enum cpufreq_xen_opt option)
+{
+    unsigned int count = cpufreq_xen_cnt;
+
+    while ( count )
+    {
+        if ( cpufreq_xen_opts[--count] == option )
+            return true;
+    }
+
+    return false;
+}
+
+static int __init cpufreq_cmdline_parse_xen(const char *arg, const char *end)
+{
+    int ret = 0;
+
+    xen_processor_pmbits |= XEN_PROCESSOR_PM_PX;
+    cpufreq_controller = FREQCTL_xen;
+    cpufreq_xen_opts[cpufreq_xen_cnt++] = CPUFREQ_xen;
+    ret = 0;
+    if ( arg[0] && arg[1] )
+        ret = cpufreq_cmdline_parse(arg + 1, end);
+
+    return ret;
+}
+
+static int __init cpufreq_cmdline_parse_hwp(const char *arg, const char *end)
+{
+    int ret = 0;
+
+    xen_processor_pmbits |= XEN_PROCESSOR_PM_PX;
+    cpufreq_controller = FREQCTL_xen;
+    cpufreq_xen_opts[cpufreq_xen_cnt++] = CPUFREQ_hwp;
+    if ( arg[0] && arg[1] )
+        ret = hwp_cmdline_parse(arg + 1, end);
+
+    return ret;
+}
+
 static int __init cf_check setup_cpufreq_option(const char *str)
 {
     const char *arg = strpbrk(str, ",:;");
@@ -112,25 +152,13 @@ static int __init cf_check setup_cpufreq_option(const char *str)
         if ( cpufreq_xen_cnt == ARRAY_SIZE(cpufreq_xen_opts) )
             return -E2BIG;
 
-        if ( choice > 0 || !cmdline_strcmp(str, "xen") )
-        {
-            xen_processor_pmbits |= XEN_PROCESSOR_PM_PX;
-            cpufreq_controller = FREQCTL_xen;
-            cpufreq_xen_opts[cpufreq_xen_cnt++] = CPUFREQ_xen;
-            ret = 0;
-            if ( arg[0] && arg[1] )
-                ret = cpufreq_cmdline_parse(arg + 1, end);
-        }
+        if ( (choice > 0 || !cmdline_strcmp(str, "xen")) &&
+             !cpufreq_opts_contain(CPUFREQ_xen) )
+            ret = cpufreq_cmdline_parse_xen(arg, end);
         else if ( IS_ENABLED(CONFIG_INTEL) && choice < 0 &&
-                  !cmdline_strcmp(str, "hwp") )
-        {
-            xen_processor_pmbits |= XEN_PROCESSOR_PM_PX;
-            cpufreq_controller = FREQCTL_xen;
-            cpufreq_xen_opts[cpufreq_xen_cnt++] = CPUFREQ_hwp;
-            ret = 0;
-            if ( arg[0] && arg[1] )
-                ret = hwp_cmdline_parse(arg + 1, end);
-        }
+                  !cmdline_strcmp(str, "hwp") &&
+                  !cpufreq_opts_contain(CPUFREQ_hwp) )
+            ret = cpufreq_cmdline_parse_hwp(arg, end);
         else
             ret = -EINVAL;
 
-- 
2.34.1