[PATCH kvmtool v2 1/6] rtc: Initialize the Register D for MC146818 RTC

From: Julien Thierry <julien.thierry@arm.com>
To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu
Cc: andre.przywara@arm.com, Sami Mujawar <sami.mujawar@arm.com>,
	will.deacon@arm.com
Subject: [PATCH kvmtool v2 1/6] rtc: Initialize the Register D for MC146818 RTC
Date: Thu, 10 Jan 2019 14:20:41 +0000	[thread overview]
Message-ID: <1547130046-14729-2-git-send-email-julien.thierry@arm.com> (raw)
In-Reply-To: <1547130046-14729-1-git-send-email-julien.thierry@arm.com>

From: Sami Mujawar <sami.mujawar@arm.com>

Some software drivers check the VRT bit (BIT7) of Register D before
using the MC146818 RTC. Initialized the VRT bit in rtc__init() to
indicate that the RAM and time contents are valid.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
---
 hw/rtc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/rtc.c b/hw/rtc.c
index 0649b5d..c1fa72f 100644
--- a/hw/rtc.c
+++ b/hw/rtc.c
@@ -25,6 +25,11 @@
 #define RTC_REG_C			0x0C
 #define RTC_REG_D			0x0D
 
+/*
+ * Register D Bits
+ */
+#define RTC_REG_D_VRT			(1 << 7)
+
 struct rtc_device {
 	u8			cmos_idx;
 	u8			cmos_data[128];
@@ -140,6 +145,9 @@ int rtc__init(struct kvm *kvm)
 		return r;
 	}
 
+	/* Set the VRT bit in Register D to indicate valid RAM and time */
+	rtc.cmos_data[RTC_REG_D] = RTC_REG_D_VRT;
+
 	return r;
 }
 dev_init(rtc__init);
-- 
1.9.1
