[xen staging] x86/time: move CMOS edge detection into read helper

[patchbot@xxxxxxx]

commit 91df743c45a5cca0de84e6ebe4651272c9656692
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Sep 9 13:41:48 2024 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 9 13:41:48 2024 +0200

    x86/time: move CMOS edge detection into read helper
    
    Move the logic that ensures the CMOS RTC data is read just after it's been
    updated into the __get_cmos_time() function that does the register reads.  
This
    requires returning a boolean from __get_cmos_time() to signal whether the 
read
    has been successfully performed after an update.
    
    Note that while __get_cmos_time() can be used without waiting for the update
    edge, so far the only caller does wait for it, hence move the code inside of
    the function.
    
    The goal, albeit not accomplished by this patch, is to be able to split the
    probing and the reading of the CMOS RTC data into two separate functions.
    
    No functional change intended.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/time.c | 50 ++++++++++++++++++++++++++------------------------
 1 file changed, 26 insertions(+), 24 deletions(-)

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 3c4cd1b595..e55e76bd63 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1246,8 +1246,26 @@ struct rtc_time {
     unsigned int year, mon, day, hour, min, sec;
 };
 
-static void __get_cmos_time(struct rtc_time *rtc)
+static bool __get_cmos_time(struct rtc_time *rtc)
 {
+    s_time_t start, t1, t2;
+    unsigned long flags;
+
+    spin_lock_irqsave(&rtc_lock, flags);
+
+    /* read RTC exactly on falling edge of update flag */
+    start = NOW();
+    do { /* may take up to 1 second... */
+        t1 = NOW() - start;
+    } while ( !(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) &&
+              t1 <= SECONDS(1) );
+
+    start = NOW();
+    do { /* must try at least 2.228 ms */
+        t2 = NOW() - start;
+    } while ( (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) &&
+              t2 < MILLISECS(3) );
+
     rtc->sec  = CMOS_READ(RTC_SECONDS);
     rtc->min  = CMOS_READ(RTC_MINUTES);
     rtc->hour = CMOS_READ(RTC_HOURS);
@@ -1265,13 +1283,17 @@ static void __get_cmos_time(struct rtc_time *rtc)
         BCD_TO_BIN(rtc->year);
     }
 
+    spin_unlock_irqrestore(&rtc_lock, flags);
+
     if ( (rtc->year += 1900) < 1970 )
         rtc->year += 100;
+
+    return t1 <= SECONDS(1) && t2 < MILLISECS(3);
 }
 
 static unsigned long get_cmos_time(void)
 {
-    unsigned long res, flags;
+    unsigned long res;
     struct rtc_time rtc;
     unsigned int seconds = 60;
     static bool __read_mostly cmos_rtc_probe;
@@ -1292,29 +1314,9 @@ static unsigned long get_cmos_time(void)
 
     for ( ; ; )
     {
-        s_time_t start, t1, t2;
-
-        spin_lock_irqsave(&rtc_lock, flags);
-
-        /* read RTC exactly on falling edge of update flag */
-        start = NOW();
-        do { /* may take up to 1 second... */
-            t1 = NOW() - start;
-        } while ( !(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) &&
-                  t1 <= SECONDS(1) );
-
-        start = NOW();
-        do { /* must try at least 2.228 ms */
-            t2 = NOW() - start;
-        } while ( (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) &&
-                  t2 < MILLISECS(3) );
-
-        __get_cmos_time(&rtc);
-
-        spin_unlock_irqrestore(&rtc_lock, flags);
+        bool success = __get_cmos_time(&rtc);
 
-        if ( likely(!cmos_rtc_probe) ||
-             t1 > SECONDS(1) || t2 >= MILLISECS(3) ||
+        if ( likely(!cmos_rtc_probe) || !success ||
              rtc.sec >= 60 || rtc.min >= 60 || rtc.hour >= 24 ||
              !rtc.day || rtc.day > 31 ||
              !rtc.mon || rtc.mon > 12 )
--
generated by git-patchbot for /home/xen/git/xen.git#staging