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Date:      Thu, 18 Oct 2012 10:29:16 +0000 (UTC)
From:      Marius Strobl <marius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r241679 - head/sys/dev/iicbus
Message-ID:  <201210181029.q9IATG46012868@svn.freebsd.org>
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Author: marius
Date: Thu Oct 18 10:29:16 2012
New Revision: 241679
URL: http://svn.freebsd.org/changeset/base/241679

Log:
  It turns out that as documented, PCF8563_R_SECOND_VL (i.e. battery low)
  doesn't automatically clear when VDD rises above Vlow again and needs to be
  cleared manually. However, apparently this needs all of the time registers
  to be set, i.e. pcf8563_settime(), and not just PCF8563_R_SECOND in order
  for PCF8563_R_SECOND_VL to stick. Thus, we just issue a warning during
  pcf8563_attach() rather than failing with ENXIO in case it is set.
  
  MFC after:	3 days

Modified:
  head/sys/dev/iicbus/pcf8563.c

Modified: head/sys/dev/iicbus/pcf8563.c
==============================================================================
--- head/sys/dev/iicbus/pcf8563.c	Thu Oct 18 09:59:50 2012	(r241678)
+++ head/sys/dev/iicbus/pcf8563.c	Thu Oct 18 10:29:16 2012	(r241679)
@@ -83,6 +83,16 @@ pcf8563_attach(device_t dev)
 	if (sc->sc_addr == 0)
 		sc->sc_addr = PCF8563_ADDR;
 
+	/*
+	 * NB: PCF8563_R_SECOND_VL doesn't automatically clear when VDD
+	 * rises above Vlow again and needs to be cleared manually.
+	 * However, apparently this needs all of the time registers to be
+	 * set, i.e. pcf8563_settime(), and not just PCF8563_R_SECOND in
+	 * order for PCF8563_R_SECOND_VL to stick.  Thus, we just issue a
+	 * warning here rather than failing with ENXIO in case it is set.
+	 * Note that pcf8563_settime() will also clear PCF8563_R_SECOND_VL
+	 * as a side-effect.
+	 */
 	msgs[0].slave = msgs[1].slave = sc->sc_addr;
 	error = iicbus_transfer(device_get_parent(dev), msgs, sizeof(msgs) /
 	    sizeof(*msgs));
@@ -90,10 +100,8 @@ pcf8563_attach(device_t dev)
 		device_printf(dev, "%s: cannot read RTC\n", __func__);
 		return (error);
 	}
-	if ((val & PCF8563_R_SECOND_VL) != 0) {
+	if ((val & PCF8563_R_SECOND_VL) != 0)
 		device_printf(dev, "%s: battery low\n", __func__);
-		return (ENXIO);
-	}
 
 	sc->sc_year0 = 1900;
 	clock_register(dev, 1000000);   /* 1 second resolution */

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