[PATCH v2 1/2] x86/time: split CMOS time fetching into wrapper

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Split the logic that deals with probing and fetching the CMOS time into a
separate helper.  While moving the code also take the opportunity to reduce the
scope of some local variables.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - New in this version.
---
 xen/arch/x86/time.c | 72 +++++++++++++++++++++++++--------------------
 1 file changed, 40 insertions(+), 32 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index a97d78484105..272ca2468ea6 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1245,29 +1245,14 @@ static void __get_cmos_time(struct rtc_time *rtc)
         rtc->year += 100;
 }
 
-static unsigned long get_cmos_time(void)
+/* Returns true when fetching time from CMOS is successful. */
+static bool read_cmos_time(struct rtc_time *rtc, bool cmos_rtc_probe)
 {
-    unsigned long res, flags;
-    struct rtc_time rtc;
     unsigned int seconds = 60;
-    static bool __read_mostly cmos_rtc_probe;
-    boolean_param("cmos-rtc-probe", cmos_rtc_probe);
-
-    if ( efi_enabled(EFI_RS) )
-    {
-        res = efi_get_time();
-        if ( res )
-            return res;
-    }
-
-    if ( likely(!(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)) )
-        cmos_rtc_probe = false;
-    else if ( system_state < SYS_STATE_smp_boot && !cmos_rtc_probe )
-        panic("System with no CMOS RTC advertised must be booted from EFI"
-              " (or with command line option \"cmos-rtc-probe\")\n");
 
     for ( ; ; )
     {
+        unsigned long flags;
         s_time_t start, t1, t2;
 
         spin_lock_irqsave(&rtc_lock, flags);
@@ -1285,33 +1270,56 @@ static unsigned long get_cmos_time(void)
         } while ( (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) &&
                   t2 < MILLISECS(3) );
 
-        __get_cmos_time(&rtc);
+        __get_cmos_time(rtc);
 
         spin_unlock_irqrestore(&rtc_lock, flags);
 
-        if ( likely(!cmos_rtc_probe) ||
-             t1 > SECONDS(1) || t2 >= MILLISECS(3) ||
-             rtc.sec >= 60 || rtc.min >= 60 || rtc.hour >= 24 ||
-             !rtc.day || rtc.day > 31 ||
-             !rtc.mon || rtc.mon > 12 )
-            break;
+        if ( likely(!cmos_rtc_probe) )
+            return true;
+
+        if ( t1 > SECONDS(1) || t2 >= MILLISECS(3) ||
+             rtc->sec >= 60 || rtc->min >= 60 || rtc->hour >= 24 ||
+             !rtc->day || rtc->day > 31 ||
+             !rtc->mon || rtc->mon > 12 )
+            return false;
 
         if ( seconds < 60 )
         {
-            if ( rtc.sec != seconds )
-            {
-                cmos_rtc_probe = false;
+            if ( rtc->sec != seconds )
                 acpi_gbl_FADT.boot_flags &= ~ACPI_FADT_NO_CMOS_RTC;
-            }
-            break;
+            return true;
         }
 
         process_pending_softirqs();
 
-        seconds = rtc.sec;
+        seconds = rtc->sec;
     }
 
-    if ( unlikely(cmos_rtc_probe) )
+    ASSERT_UNREACHABLE();
+    return false;
+}
+
+static unsigned long get_cmos_time(void)
+{
+    struct rtc_time rtc;
+    static bool __read_mostly cmos_rtc_probe;
+    boolean_param("cmos-rtc-probe", cmos_rtc_probe);
+
+    if ( efi_enabled(EFI_RS) )
+    {
+        unsigned long res = efi_get_time();
+
+        if ( res )
+            return res;
+    }
+
+    if ( likely(!(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)) )
+        cmos_rtc_probe = false;
+    else if ( system_state < SYS_STATE_smp_boot && !cmos_rtc_probe )
+        panic("System with no CMOS RTC advertised must be booted from EFI"
+              " (or with command line option \"cmos-rtc-probe\")\n");
+
+    if ( unlikely(!read_cmos_time(&rtc, cmos_rtc_probe)) )
         panic("No CMOS RTC found - system must be booted from EFI\n");
 
     return mktime(rtc.year, rtc.mon, rtc.day, rtc.hour, rtc.min, rtc.sec);
-- 
2.46.0