From 6ade2b6b0c03648ce44f38c4b76c41c6c9df51c5 Mon Sep 17 00:00:00 2001
From: Yuanyuan Zhao <yuanyuan.zhao@linux.intel.com>
Date: Thu, 21 Apr 2022 14:22:53 +0800
Subject: [PATCH] hv: support 12 hour mode

Add support for hour format.
Bit 1 of register B indicates the hour byte format. When it's 0,
twelve-hour mode is selected. Then the seventh bit of hour register
presents AM as 0 and PM as 1.

Tracked-On: #7440
Signed-off-by: Yuanyuan Zhao <yuanyuan.zhao@linux.intel.com>
Reviewed-by: Junjie Mao <junjie.mao@intel.com>
---
 hypervisor/dm/vrtc.c                | 74 ++++++++++++++++++++++++++++-
 hypervisor/include/dm/mc146818rtc.h |  1 +
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/hypervisor/dm/vrtc.c b/hypervisor/dm/vrtc.c
index 27a1d8b63..62011f18b 100644
--- a/hypervisor/dm/vrtc.c
+++ b/hypervisor/dm/vrtc.c
@@ -238,11 +238,12 @@ static time_t rtc_to_secs(const struct acrn_vrtc *vrtc)
 	struct clktime ct;
 	time_t second = VRTC_BROKEN_TIME;
 	const struct rtcdev *rtc= &vrtc->rtcdev;
+	uint32_t hour = 0, pm = 0;
 	uint32_t century = 0, year = 0;
 
 	do {
 		if ((rtcget(rtc, rtc->sec, &ct.sec) < 0) || (rtcget(rtc, rtc->min, &ct.min) < 0) ||
-				(rtcget(rtc, rtc->hour, &ct.hour) < 0) || (rtcget(rtc, rtc->day_of_month, &ct.day) < 0) ||
+				(rtcget(rtc, rtc->day_of_month, &ct.day) < 0) ||
 				(rtcget(rtc, rtc->month, &ct.mon) < 0) || (rtcget(rtc, rtc->year, &year) < 0) ||
 				(rtcget(rtc, rtc->century, &century) < 0)) {
 			pr_err("Invalid RTC sec %#x hour %#x day %#x mon %#x year %#x century %#x\n",
@@ -251,6 +252,46 @@ static time_t rtc_to_secs(const struct acrn_vrtc *vrtc)
 			break;
 		}
 
+		/*
+		 * If 12 hour format is inuse, translate it to 24 hour format here.
+		 */
+		pm = 0;
+		hour = rtc->hour;
+		if ((rtc->reg_b & RTCSB_24HR) == 0) {
+			if (hour & 0x80U) {
+				hour &= ~0x80U;
+				pm = 1;
+			}
+		}
+		if (rtcget(rtc, hour, &ct.hour) != 0) {
+			pr_err("Invalid RTC hour %#x\n", rtc->hour);
+			break;
+		}
+		if ((rtc->reg_b & RTCSB_24HR) == 0) {
+			if ((ct.hour >= 1) && (ct.hour <= 12)) {
+				/*
+				 * Convert from 12-hour format to internal 24-hour
+				 * representation as follows:
+				 *
+				 *    12-hour format		ct.hour
+				 *	12	AM		0
+				 *	1 - 11	AM		1 - 11
+				 *	12	PM		12
+				 *	1 - 11	PM		13 - 23
+				 */
+				if (ct.hour == 12) {
+					ct.hour = 0;
+				}
+				if (pm) {
+					ct.hour += 12;
+				}
+			} else {
+				pr_err("Invalid RTC 12-hour format %#x/%d\n",
+						rtc->hour, ct.hour);
+				break;
+			}
+		}
+
 		/*
 		 * Ignore 'rtc->dow' because some guests like Linux don't bother
 		 * setting it at all while others like OpenBSD/i386 set it incorrectly.
@@ -285,12 +326,41 @@ static void secs_to_rtc(time_t rtctime, struct acrn_vrtc *vrtc)
 {
 	struct clktime ct;
 	struct rtcdev *rtc;
+	uint32_t hour;
 
 	if ((rtctime > 0) && (clk_ts_to_ct(rtctime, &ct) == 0)) {
 		rtc = &vrtc->rtcdev;
 		rtc->sec = rtcset(rtc, ct.sec);
 		rtc->min = rtcset(rtc, ct.min);
-		rtc->hour = rtcset(rtc, ct.hour);
+
+		if (rtc->reg_b & RTCSB_24HR) {
+			hour = ct.hour;
+		} else {
+			/*
+			 * Convert to the 12-hour format.
+			 */
+			switch (ct.hour) {
+			case 0:			/* 12 AM */
+			case 12:		/* 12 PM */
+				hour = 12;
+				break;
+			default:
+				/*
+				 * The remaining 'ct.hour' values are interpreted as:
+				 * [1  - 11] ->  1 - 11 AM
+				 * [13 - 23] ->  1 - 11 PM
+				 */
+				hour = ct.hour % 12;
+				break;
+			}
+		}
+
+		rtc->hour = rtcset(rtc, hour);
+
+		if (((rtc->reg_b & RTCSB_24HR) == 0) && (ct.hour >= 12)) {
+			rtc->hour |= 0x80;	    /* set MSB to indicate PM */
+		}
+
 		rtc->day_of_week = rtcset(rtc, ct.dow + 1);
 		rtc->day_of_month = rtcset(rtc, ct.day);
 		rtc->month = rtcset(rtc, ct.mon);
diff --git a/hypervisor/include/dm/mc146818rtc.h b/hypervisor/include/dm/mc146818rtc.h
index 2b95d5165..96590d1e2 100644
--- a/hypervisor/include/dm/mc146818rtc.h
+++ b/hypervisor/include/dm/mc146818rtc.h
@@ -58,6 +58,7 @@
 #define RTCSA_TUP	0x80U	/* time update, don't look now */
 
 #define RTC_STATUSB	0x0b	/* status register B */
+#define RTCSB_24HR	0x02U	/* 0 = 12 hours, 1 = 24	hours */
 #define RTCSB_BCD	0x04U	/* 0 = BCD, 1 =	Binary coded time */
 
 #define RTC_INTR	0x0c	/* status register C (R) interrupt source */