ds1307: add support for the EPSON RX-8035SA I2C RTC

The EPSON RX-8035SA I2C RTC has a similar time register layout to the
ds1307 family, with some minor differences in bit positions, polarity
and control registers.  Further generalize ds1307 to make it easier
to add more compatible chips and add support for the EPSON RX-8035SA.

MFC after:	6 days
Sponsored by:	Traverse Technologies
Differential Revision: https://reviews.freebsd.org/D35837

2 files changed, 215 insertions, 55 deletions

diff --git a/sys/dev/iicbus/ds1307.c b/sys/dev/iicbus/ds1307.c
index 2ba712400fe4..e14f10631fd5 100644
--- a/sys/dev/iicbus/ds1307.c
+++ b/sys/dev/iicbus/ds1307.c
@@ -1,5 +1,6 @@
 /*-
  * Copyright (c) 2015 Luiz Otavio O Souza <loos@FreeBSD.org>
+ * Copyright (c) 2022 Mathew McBride <matt@traverse.com.au>
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -54,23 +55,31 @@ __FBSDID("$FreeBSD$");
 #include "clock_if.h"
 #include "iicbus_if.h"
 
+enum {
+	TYPE_DS1307,
+	TYPE_MAXIM1307,
+	TYPE_MICROCHIP_MCP7491X,
+	TYPE_EPSON_RX8035,
+	TYPE_COUNT
+};
+
 struct ds1307_softc {
-	device_t	sc_dev;
-	struct intr_config_hook
-			enum_hook;
-	uint8_t		sc_ctrl;
-	bool		sc_mcp7941x;
-	bool		sc_use_ampm;
+	device_t			sc_dev;
+	struct intr_config_hook		enum_hook;
+	uint32_t			chiptype;
+	uint8_t				sc_ctrl;
+	bool				sc_use_ampm;
 };
 
 static void ds1307_start(void *);
 
 #ifdef FDT
 static const struct ofw_compat_data ds1307_compat_data[] = {
-    {"dallas,ds1307",		(uintptr_t)"Dallas DS1307 RTC"},
-    {"maxim,ds1307",		(uintptr_t)"Maxim DS1307 RTC"},
-    {"microchip,mcp7941x",	(uintptr_t)"Microchip MCP7941x RTC"},
-    { NULL, 0 }
+	{"dallas,ds1307",		TYPE_DS1307},
+	{"maxim,ds1307",		TYPE_MAXIM1307},
+	{"microchip,mcp7941x",		TYPE_MICROCHIP_MCP7491X},
+	{"epson,rx8035",		TYPE_EPSON_RX8035},
+	{ NULL, 0 }
 };
 #endif
 
@@ -96,7 +105,8 @@ ds1307_ctrl_read(struct ds1307_softc *sc)
 	sc->sc_ctrl = 0;
 	error = ds1307_read1(sc->sc_dev, DS1307_CONTROL, &sc->sc_ctrl);
 	if (error) {
-		device_printf(sc->sc_dev, "cannot read from RTC.\n");
+		device_printf(sc->sc_dev, "%s: cannot read from RTC: %d\n",
+		    __func__, error);
 		return (error);
 	}
 
@@ -112,7 +122,8 @@ ds1307_ctrl_write(struct ds1307_softc *sc)
 	ctrl = sc->sc_ctrl & DS1307_CTRL_MASK;
 	error = ds1307_write1(sc->sc_dev, DS1307_CONTROL, ctrl);
 	if (error != 0)
-		device_printf(sc->sc_dev, "cannot write to RTC.\n");
+		device_printf(sc->sc_dev, "%s: cannot write to RTC: %d\n",
+		    __func__, error);
 
 	return (error);
 }
@@ -127,7 +138,7 @@ ds1307_sqwe_sysctl(SYSCTL_HANDLER_ARGS)
 	error = ds1307_ctrl_read(sc);
 	if (error != 0)
 		return (error);
-	if (sc->sc_mcp7941x)
+	if (sc->chiptype == TYPE_MICROCHIP_MCP7491X)
 		sqwe_bit = MCP7941X_CTRL_SQWE;
 	else
 		sqwe_bit = DS1307_CTRL_SQWE;
@@ -216,11 +227,29 @@ ds1307_probe(device_t dev)
 		return (ENXIO);
 
 	compat = ofw_bus_search_compatible(dev, ds1307_compat_data);
-	if (compat->ocd_str != NULL) {
-		device_set_desc(dev, (const char *)compat->ocd_data);
-		return (BUS_PROBE_DEFAULT);
+	if (compat->ocd_str == NULL)
+		return (ENXIO);
+
+	switch(compat->ocd_data) {
+		case TYPE_DS1307:
+			device_set_desc(dev, "Dallas DS1307");
+			break;
+		case TYPE_MAXIM1307:
+			device_set_desc(dev, "Maxim DS1307");
+			break;
+		case TYPE_MICROCHIP_MCP7491X:
+			device_set_desc(dev, "Microchip MCP7491X");
+			break;
+		case TYPE_EPSON_RX8035:
+			device_set_desc(dev, "Epson RX-8035");
+			break;
+		default:
+			device_set_desc(dev, "Unknown DS1307-like device");
+			break;
 	}
+	return (BUS_PROBE_DEFAULT);
 #endif
+
 	device_set_desc(dev, "Maxim DS1307 RTC");
 	return (BUS_PROBE_NOWILDCARD);
 }
@@ -228,16 +257,23 @@ ds1307_probe(device_t dev)
 static int
 ds1307_attach(device_t dev)
 {
+#ifdef FDT
+	const struct ofw_compat_data *compat;
+#endif
 	struct ds1307_softc *sc;
 
 	sc = device_get_softc(dev);
 	sc->sc_dev = dev;
 	sc->enum_hook.ich_func = ds1307_start;
 	sc->enum_hook.ich_arg = dev;
-
 #ifdef FDT
-	if (ofw_bus_is_compatible(dev, "microchip,mcp7941x"))
-		sc->sc_mcp7941x = 1;
+	compat = ofw_bus_search_compatible(dev, ds1307_compat_data);
+	sc->chiptype = compat->ocd_data;
+	/* Unify the chiptypes to DS1307 where possible. */
+	if (sc->chiptype == TYPE_MAXIM1307)
+		sc->chiptype = TYPE_DS1307;
+#else
+	sc->chiptype = TYPE_DS1307;
 #endif
 
 	/*
@@ -258,6 +294,110 @@ ds1307_detach(device_t dev)
 	return (0);
 }
 
+static bool
+is_epson_time_valid(struct ds1307_softc *sc)
+{
+	device_t dev;
+	int error;
+	uint8_t ctrl2;
+
+	dev = sc->sc_dev;
+
+	/*
+	 * The RX-8035 single register read is non-standard
+	 * Refer to section 8.9.5 of the RX-8035 application manual:
+	 * "I2C bus basic transfer format", under "Standard Read Method".
+	 * Basically, register to read goes into the top 4 bits.
+	 */
+	error = ds1307_read1(dev, (RX8035_CTRL_2 << 4), &ctrl2);
+	if (error) {
+		device_printf(dev, "%s cannot read Control 2 register: %d\n",
+		    __func__, error);
+		return (false);
+	}
+
+	if (ctrl2 & RX8035_CTRL_2_XSTP) {
+		device_printf(dev, "Oscillation stop detected (ctrl2=%#02x)\n",
+		    ctrl2);
+		return (false);
+	}
+
+	/*
+	 * Power on reset (PON) generally implies oscillation stop,
+	 * but catch it as well to be sure.
+	 */
+	if (ctrl2 & RX8035_CTRL_2_PON) {
+		device_printf(dev, "Power-on reset detected (ctrl2=%#02x)\n",
+		    ctrl2);
+		return (false);
+	}
+
+	return (true);
+}
+
+static int
+mark_epson_time_valid(struct ds1307_softc *sc)
+{
+	device_t dev;
+	int error;
+	uint8_t ctrl2;
+	uint8_t control_mask;
+
+	dev = sc->sc_dev;
+
+	error = ds1307_read1(dev, (RX8035_CTRL_2 << 4), &ctrl2);
+	if (error) {
+		device_printf(dev, "%s cannot read Control 2 register: %d\n",
+		    __func__, error);
+		return (false);
+	}
+
+	control_mask = (RX8035_CTRL_2_PON | RX8035_CTRL_2_XSTP | RX8035_CTRL_2_VDET);
+	ctrl2 = ctrl2 & ~(control_mask);
+
+	error = ds1307_write1(dev, (RX8035_CTRL_2 << 4), ctrl2);
+	if (error) {
+		device_printf(dev, "%s cannot write to Control 2 register: %d\n",
+		    __func__, error);
+		return (false);
+	}
+	return (true);
+}
+
+static bool is_dev_time_valid(struct ds1307_softc *sc)
+{
+	device_t dev;
+	int error;
+	uint8_t osc_en;
+	uint8_t secs;
+
+	/* Epson RTCs have different control/status registers. */
+	if (sc->chiptype == TYPE_EPSON_RX8035)
+		return (is_epson_time_valid(sc));
+
+	dev = sc->sc_dev;
+	/* Check if the oscillator is disabled. */
+	error = ds1307_read1(dev, DS1307_SECS, &secs);
+	if (error) {
+		device_printf(dev, "%s: cannot read from RTC: %d\n",
+		    __func__, error);
+		return (false);
+	}
+
+	switch (sc->chiptype) {
+	case TYPE_MICROCHIP_MCP7491X:
+		osc_en = 0x80;
+		break;
+	default:
+		osc_en = 0x00;
+		break;
+	}
+	if (((secs & DS1307_SECS_CH) ^ osc_en) != 0)
+		return (false);
+
+	return (true);
+}
+
 static void
 ds1307_start(void *xdev)
 {
@@ -266,33 +406,28 @@ ds1307_start(void *xdev)
 	struct sysctl_ctx_list *ctx;
 	struct sysctl_oid *tree_node;
 	struct sysctl_oid_list *tree;
-	uint8_t secs;
-	uint8_t osc_en;
 
 	dev = (device_t)xdev;
 	sc = device_get_softc(dev);
-	ctx = device_get_sysctl_ctx(dev);
-	tree_node = device_get_sysctl_tree(dev);
-	tree = SYSCTL_CHILDREN(tree_node);
 
 	config_intrhook_disestablish(&sc->enum_hook);
 
-	/* Check if the oscillator is disabled. */
-	if (ds1307_read1(sc->sc_dev, DS1307_SECS, &secs) != 0) {
-		device_printf(sc->sc_dev, "cannot read from RTC.\n");
-		return;
-	}
-	if (sc->sc_mcp7941x)
-		osc_en = 0x80;
-	else
-		osc_en = 0x00;
-
-	if (((secs & DS1307_SECS_CH) ^ osc_en) != 0) {
-		device_printf(sc->sc_dev,
+	if (!is_dev_time_valid(sc))
+		device_printf(dev,
 		    "WARNING: RTC clock stopped, check the battery.\n");
-	}
 
-	/* Configuration parameters. */
+	/*
+	 * Configuration parameters:
+	 * square wave output cannot be changed or inhibited on the RX-8035,
+	 * so don't present the sysctls there.
+	 */
+	if (sc->chiptype == TYPE_EPSON_RX8035)
+		goto skip_sysctl;
+
+	ctx = device_get_sysctl_ctx(dev);
+	tree_node = device_get_sysctl_tree(dev);
+	tree = SYSCTL_CHILDREN(tree_node);
+
 	SYSCTL_ADD_PROC(ctx, tree, OID_AUTO, "sqwe",
 	    CTLFLAG_RW | CTLTYPE_UINT | CTLFLAG_MPSAFE, sc, 0,
 	    ds1307_sqwe_sysctl, "IU", "DS1307 square-wave enable");
@@ -303,6 +438,7 @@ ds1307_start(void *xdev)
 	SYSCTL_ADD_PROC(ctx, tree, OID_AUTO, "sqw_out",
 	    CTLFLAG_RW | CTLTYPE_UINT | CTLFLAG_MPSAFE, sc, 0,
 	    ds1307_sqw_out_sysctl, "IU", "DS1307 square-wave output state");
+skip_sysctl:
 
 	/*
 	 * Register as a clock with 1 second resolution.  Schedule the
@@ -316,30 +452,36 @@ ds1307_start(void *xdev)
 static int
 ds1307_gettime(device_t dev, struct timespec *ts)
 {
-	int error;
 	struct bcd_clocktime bct;
 	struct ds1307_softc *sc;
-	uint8_t data[7], hourmask, st_mask;
+	int error;
+	uint8_t data[7], hourmask, ampm_mode;
 
 	sc = device_get_softc(dev);
 	error = iicdev_readfrom(sc->sc_dev, DS1307_SECS, data, sizeof(data),
 	    IIC_INTRWAIT);
 	if (error != 0) {
-		device_printf(dev, "cannot read from RTC.\n");
+		device_printf(dev, "%s: cannot read from RTC: %d\n",
+		    __func__, error);
 		return (error);
 	}
 
-	/* If the clock halted, we don't have good data. */
-	if (sc->sc_mcp7941x)
-		st_mask = 0x80;
-	else
-		st_mask = 0x00;
-
-	if (((data[DS1307_SECS] & DS1307_SECS_CH) ^ st_mask) != 0)
+	if (!is_dev_time_valid(sc)) {
+		device_printf(dev, "Device time not valid.\n");
 		return (EINVAL);
+	}
 
-	/* If chip is in AM/PM mode remember that. */
-	if (data[DS1307_HOUR] & DS1307_HOUR_USE_AMPM) {
+	/*
+	 * If the chip is in AM/PM mode remember that.
+	 * The EPSON uses a 1 to signify 24 hour mode, while the DS uses a 0,
+	 * in slighly different positions.
+	 */
+	if (sc->chiptype == TYPE_EPSON_RX8035)
+		ampm_mode = !(data[DS1307_HOUR] & RX8035_HOUR_USE_24);
+	else
+		ampm_mode = data[DS1307_HOUR] & DS1307_HOUR_USE_AMPM;
+
+	if (ampm_mode) {
 		sc->sc_use_ampm = true;
 		hourmask = DS1307_HOUR_MASK_12HR;
 	} else
@@ -377,12 +519,19 @@ ds1307_settime(device_t dev, struct timespec *ts)
 	clock_ts_to_bcd(ts, &bct, sc->sc_use_ampm);
 	clock_dbgprint_bcd(sc->sc_dev, CLOCK_DBG_WRITE, &bct);
 
-	/* If the chip is in AM/PM mode, adjust hour and set flags as needed. */
+	/*
+	 * If the chip is in AM/PM mode, adjust hour and set flags as needed.
+	 * The AM/PM bit polarity and position is different on the EPSON.
+	 */
 	if (sc->sc_use_ampm) {
-		pmflags = DS1307_HOUR_USE_AMPM;
+		pmflags = (sc->chiptype != TYPE_EPSON_RX8035) ?
+				DS1307_HOUR_USE_AMPM : 0;
 		if (bct.ispm)
 			pmflags |= DS1307_HOUR_IS_PM;
-	} else
+
+	} else if (sc->chiptype == TYPE_EPSON_RX8035)
+		pmflags = RX8035_HOUR_USE_24;
+	else
 		pmflags = 0;
 
 	data[DS1307_SECS]    = bct.sec;
@@ -392,18 +541,23 @@ ds1307_settime(device_t dev, struct timespec *ts)
 	data[DS1307_WEEKDAY] = bct.dow;
 	data[DS1307_MONTH]   = bct.mon;
 	data[DS1307_YEAR]    = bct.year & 0xff;
-	if (sc->sc_mcp7941x) {
+	if (sc->chiptype == TYPE_MICROCHIP_MCP7491X) {
 		data[DS1307_SECS] |= MCP7941X_SECS_ST;
 		data[DS1307_WEEKDAY] |= MCP7941X_WEEKDAY_VBATEN;
 		year = bcd2bin(bct.year >> 8) * 100 + bcd2bin(bct.year & 0xff);
 		if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
 			data[DS1307_MONTH] |= MCP7941X_MONTH_LPYR;
 	}
+
 	/* Write the time back to RTC. */
 	error = iicdev_writeto(sc->sc_dev, DS1307_SECS, data, sizeof(data),
 	    IIC_INTRWAIT);
 	if (error != 0)
-		device_printf(dev, "cannot write to RTC.\n");
+		device_printf(dev, "%s: cannot write to RTC: %d\n",
+		    __func__, error);
+
+	if (sc->chiptype == TYPE_EPSON_RX8035)
+		error = mark_epson_time_valid(sc);
 
 	return (error);
 }
diff --git a/sys/dev/iicbus/ds1307reg.h b/sys/dev/iicbus/ds1307reg.h
index f2763a5e0cd3..e4f7979c97da 100644
--- a/sys/dev/iicbus/ds1307reg.h
+++ b/sys/dev/iicbus/ds1307reg.h
@@ -44,6 +44,7 @@
 #define	DS1307_HOUR_MASK_24HR		0x3f
 #define	DS1307_HOUR_IS_PM		0x20
 #define	DS1307_HOUR_USE_AMPM		0x40
+#define	RX8035_HOUR_USE_24		0x80
 #define	DS1307_WEEKDAY		0x03
 #define	MCP7941X_WEEKDAY_VBATEN		0x08
 #define	DS1307_WEEKDAY_MASK		0x07
@@ -63,4 +64,9 @@
 #define	DS1307_CTRL_RS_MASK		(DS1307_CTRL_RS1 | DS1307_CTRL_RS0)
 #define	DS1307_CTRL_MASK		0x93
 
+#define	RX8035_CTRL_2			0x0F
+#define	RX8035_CTRL_2_PON		(1 << 4)
+#define	RX8035_CTRL_2_XSTP		(1 << 5)
+#define	RX8035_CTRL_2_VDET		(1 << 6)
+
 #endif	/* _DS1307REG_H_ */