rtc: rtc-dm355evm driver

Simple RTC driver for the MSP430 firmware on the DM355 EVM board. Other than not supporting atomic reads/writes of all four bytes, this is reasonable as a basic no-alarm RTC. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

rtc: rtc-dm355evm driver
Simple RTC driver for the MSP430 firmware on the DM355 EVM board. Other than not supporting atomic reads/writes of all four bytes, this is reasonable as a basic no-alarm RTC. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
David Brownell · Linus Torvalds
1 parent 77a592655c
Showing 3 changed files with 182 additions and 0 deletions Side-by-side Diff
drivers/rtc/Kconfig
drivers/rtc/Makefile
drivers/rtc/rtc-dm355evm.c
@@ -241,6 +241,12 @@
 	  If you say Y here you will get support for the
 	  watchdog timer in the ST M41T60 and M41T80 RTC chips series.
  
+config RTC_DRV_DM355EVM
+	tristate "TI DaVinci DM355 EVM RTC"
+	depends on MFD_DM355EVM_MSP
+	help
+	  Supports the RTC firmware in the MSP430 on the DM355 EVM.
+
 config RTC_DRV_TWL92330
 	boolean "TI TWL92330/Menelaus"
 	depends on MENELAUS
@@ -23,6 +23,7 @@
 obj-$(CONFIG_RTC_DRV_AU1XXX)	+= rtc-au1xxx.o
 obj-$(CONFIG_RTC_DRV_BFIN)	+= rtc-bfin.o
 obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc-cmos.o
+obj-$(CONFIG_RTC_DRV_DM355EVM)	+= rtc-dm355evm.o
 obj-$(CONFIG_RTC_DRV_DS1216)	+= rtc-ds1216.o
 obj-$(CONFIG_RTC_DRV_DS1286)	+= rtc-ds1286.o
 obj-$(CONFIG_RTC_DRV_DS1302)	+= rtc-ds1302.o
+/*
+ * rtc-dm355evm.c - access battery-backed counter in MSP430 firmware
+ *
+ * Copyright (c) 2008 by David Brownell
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+
+#include <linux/i2c/dm355evm_msp.h>
+
+
+/*
+ * The MSP430 firmware on the DM355 EVM uses a watch crystal to feed
+ * a 1 Hz counter.  When a backup battery is supplied, that makes a
+ * reasonable RTC for applications where alarms and non-NTP drift
+ * compensation aren't important.
+ *
+ * The only real glitch is the inability to read or write all four
+ * counter bytes atomically:  the count may increment in the middle
+ * of an operation, causing trouble when the LSB rolls over.
+ *
+ * This driver was tested with firmware revision A4.
+ */
+union evm_time {
+	u8	bytes[4];
+	u32	value;
+};
+
+static int dm355evm_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	union evm_time	time;
+	int		status;
+	int		tries = 0;
+
+	do {
+		/*
+		 * Read LSB(0) to MSB(3) bytes.  Defend against the counter
+		 * rolling over by re-reading until the value is stable,
+		 * and assuming the four reads take at most a few seconds.
+		 */
+		status = dm355evm_msp_read(DM355EVM_MSP_RTC_0);
+		if (status < 0)
+			return status;
+		if (tries && time.bytes[0] == status)
+			break;
+		time.bytes[0] = status;
+
+		status = dm355evm_msp_read(DM355EVM_MSP_RTC_1);
+		if (status < 0)
+			return status;
+		if (tries && time.bytes[1] == status)
+			break;
+		time.bytes[1] = status;
+
+		status = dm355evm_msp_read(DM355EVM_MSP_RTC_2);
+		if (status < 0)
+			return status;
+		if (tries && time.bytes[2] == status)
+			break;
+		time.bytes[2] = status;
+
+		status = dm355evm_msp_read(DM355EVM_MSP_RTC_3);
+		if (status < 0)
+			return status;
+		if (tries && time.bytes[3] == status)
+			break;
+		time.bytes[3] = status;
+
+	} while (++tries < 5);
+
+	dev_dbg(dev, "read timestamp %08x\n", time.value);
+
+	rtc_time_to_tm(le32_to_cpu(time.value), tm);
+	return 0;
+}
+
+static int dm355evm_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	union evm_time	time;
+	unsigned long	value;
+	int		status;
+
+	rtc_tm_to_time(tm, &value);
+	time.value = cpu_to_le32(value);
+
+	dev_dbg(dev, "write timestamp %08x\n", time.value);
+
+	/*
+	 * REVISIT handle non-atomic writes ... maybe just retry until
+	 * byte[1] sticks (no rollover)?
+	 */
+	status = dm355evm_msp_write(time.bytes[0], DM355EVM_MSP_RTC_0);
+	if (status < 0)
+		return status;
+
+	status = dm355evm_msp_write(time.bytes[1], DM355EVM_MSP_RTC_1);
+	if (status < 0)
+		return status;
+
+	status = dm355evm_msp_write(time.bytes[2], DM355EVM_MSP_RTC_2);
+	if (status < 0)
+		return status;
+
+	status = dm355evm_msp_write(time.bytes[3], DM355EVM_MSP_RTC_3);
+	if (status < 0)
+		return status;
+
+	return 0;
+}
+
+static struct rtc_class_ops dm355evm_rtc_ops = {
+	.read_time	= dm355evm_rtc_read_time,
+	.set_time	= dm355evm_rtc_set_time,
+};
+
+/*----------------------------------------------------------------------*/
+
+static int __devinit dm355evm_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_device *rtc;
+
+	rtc = rtc_device_register(pdev->name,
+				  &pdev->dev, &dm355evm_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc)) {
+		dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
+			PTR_ERR(rtc));
+		return PTR_ERR(rtc);
+	}
+	platform_set_drvdata(pdev, rtc);
+
+	return 0;
+}
+
+static int __devexit dm355evm_rtc_remove(struct platform_device *pdev)
+{
+	struct rtc_device *rtc = platform_get_drvdata(pdev);
+
+	rtc_device_unregister(rtc);
+	platform_set_drvdata(pdev, NULL);
+	return 0;
+}
+
+/*
+ * I2C is used to talk to the MSP430, but this platform device is
+ * exposed by an MFD driver that manages I2C communications.
+ */
+static struct platform_driver rtc_dm355evm_driver = {
+	.probe		= dm355evm_rtc_probe,
+	.remove		= __devexit_p(dm355evm_rtc_remove),
+	.driver		= {
+		.owner	= THIS_MODULE,
+		.name	= "rtc-dm355evm",
+	},
+};
+
+static int __init dm355evm_rtc_init(void)
+{
+	return platform_driver_register(&rtc_dm355evm_driver);
+}
+module_init(dm355evm_rtc_init);
+
+static void __exit dm355evm_rtc_exit(void)
+{
+	platform_driver_unregister(&rtc_dm355evm_driver);
+}
+module_exit(dm355evm_rtc_exit);
+
+MODULE_LICENSE("GPL");
...	...	@@ -241,6 +241,12 @@
241	241	If you say Y here you will get support for the
242	242	watchdog timer in the ST M41T60 and M41T80 RTC chips series.
243	243
	244	+config RTC_DRV_DM355EVM
	245	+ tristate "TI DaVinci DM355 EVM RTC"
	246	+ depends on MFD_DM355EVM_MSP
	247	+ help
	248	+ Supports the RTC firmware in the MSP430 on the DM355 EVM.
	249	+
244	250	config RTC_DRV_TWL92330
245	251	boolean "TI TWL92330/Menelaus"
246	252	depends on MENELAUS
...	...	@@ -23,6 +23,7 @@
23	23	obj-$(CONFIG_RTC_DRV_AU1XXX) += rtc-au1xxx.o
24	24	obj-$(CONFIG_RTC_DRV_BFIN) += rtc-bfin.o
25	25	obj-$(CONFIG_RTC_DRV_CMOS) += rtc-cmos.o
	26	+obj-$(CONFIG_RTC_DRV_DM355EVM) += rtc-dm355evm.o
26	27	obj-$(CONFIG_RTC_DRV_DS1216) += rtc-ds1216.o
27	28	obj-$(CONFIG_RTC_DRV_DS1286) += rtc-ds1286.o
28	29	obj-$(CONFIG_RTC_DRV_DS1302) += rtc-ds1302.o
	1	+/*
	2	+ * rtc-dm355evm.c - access battery-backed counter in MSP430 firmware
	3	+ *
	4	+ * Copyright (c) 2008 by David Brownell
	5	+ *
	6	+ * This program is free software; you can redistribute it and/or
	7	+ * modify it under the terms of the GNU General Public License
	8	+ * as published by the Free Software Foundation; either version
	9	+ * 2 of the License, or (at your option) any later version.
	10	+ */
	11	+#include <linux/kernel.h>
	12	+#include <linux/init.h>
	13	+#include <linux/rtc.h>
	14	+#include <linux/platform_device.h>
	15	+
	16	+#include <linux/i2c/dm355evm_msp.h>
	17	+
	18	+
	19	+/*
	20	+ * The MSP430 firmware on the DM355 EVM uses a watch crystal to feed
	21	+ * a 1 Hz counter. When a backup battery is supplied, that makes a
	22	+ * reasonable RTC for applications where alarms and non-NTP drift
	23	+ * compensation aren't important.
	24	+ *
	25	+ * The only real glitch is the inability to read or write all four
	26	+ * counter bytes atomically: the count may increment in the middle
	27	+ * of an operation, causing trouble when the LSB rolls over.
	28	+ *
	29	+ * This driver was tested with firmware revision A4.
	30	+ */
	31	+union evm_time {
	32	+ u8 bytes[4];
	33	+ u32 value;
	34	+};
	35	+
	36	+static int dm355evm_rtc_read_time(struct device dev, struct rtc_time tm)
	37	+{
	38	+ union evm_time time;
	39	+ int status;
	40	+ int tries = 0;
	41	+
	42	+ do {
	43	+ /*
	44	+ * Read LSB(0) to MSB(3) bytes. Defend against the counter
	45	+ * rolling over by re-reading until the value is stable,
	46	+ * and assuming the four reads take at most a few seconds.
	47	+ */
	48	+ status = dm355evm_msp_read(DM355EVM_MSP_RTC_0);
	49	+ if (status < 0)
	50	+ return status;
	51	+ if (tries && time.bytes[0] == status)
	52	+ break;
	53	+ time.bytes[0] = status;
	54	+
	55	+ status = dm355evm_msp_read(DM355EVM_MSP_RTC_1);
	56	+ if (status < 0)
	57	+ return status;
	58	+ if (tries && time.bytes[1] == status)
	59	+ break;
	60	+ time.bytes[1] = status;
	61	+
	62	+ status = dm355evm_msp_read(DM355EVM_MSP_RTC_2);
	63	+ if (status < 0)
	64	+ return status;
	65	+ if (tries && time.bytes[2] == status)
	66	+ break;
	67	+ time.bytes[2] = status;
	68	+
	69	+ status = dm355evm_msp_read(DM355EVM_MSP_RTC_3);
	70	+ if (status < 0)
	71	+ return status;
	72	+ if (tries && time.bytes[3] == status)
	73	+ break;
	74	+ time.bytes[3] = status;
	75	+
	76	+ } while (++tries < 5);
	77	+
	78	+ dev_dbg(dev, "read timestamp %08x\n", time.value);
	79	+
	80	+ rtc_time_to_tm(le32_to_cpu(time.value), tm);
	81	+ return 0;
	82	+}
	83	+
	84	+static int dm355evm_rtc_set_time(struct device dev, struct rtc_time tm)
	85	+{
	86	+ union evm_time time;
	87	+ unsigned long value;
	88	+ int status;
	89	+
	90	+ rtc_tm_to_time(tm, &value);
	91	+ time.value = cpu_to_le32(value);
	92	+
	93	+ dev_dbg(dev, "write timestamp %08x\n", time.value);
	94	+
	95	+ /*
	96	+ * REVISIT handle non-atomic writes ... maybe just retry until
	97	+ * byte[1] sticks (no rollover)?
	98	+ */
	99	+ status = dm355evm_msp_write(time.bytes[0], DM355EVM_MSP_RTC_0);
	100	+ if (status < 0)
	101	+ return status;
	102	+
	103	+ status = dm355evm_msp_write(time.bytes[1], DM355EVM_MSP_RTC_1);
	104	+ if (status < 0)
	105	+ return status;
	106	+
	107	+ status = dm355evm_msp_write(time.bytes[2], DM355EVM_MSP_RTC_2);
	108	+ if (status < 0)
	109	+ return status;
	110	+
	111	+ status = dm355evm_msp_write(time.bytes[3], DM355EVM_MSP_RTC_3);
	112	+ if (status < 0)
	113	+ return status;
	114	+
	115	+ return 0;
	116	+}
	117	+
	118	+static struct rtc_class_ops dm355evm_rtc_ops = {
	119	+ .read_time = dm355evm_rtc_read_time,
	120	+ .set_time = dm355evm_rtc_set_time,
	121	+};
	122	+
	123	+/----------------------------------------------------------------------/
	124	+
	125	+static int __devinit dm355evm_rtc_probe(struct platform_device *pdev)
	126	+{
	127	+ struct rtc_device *rtc;
	128	+
	129	+ rtc = rtc_device_register(pdev->name,
	130	+ &pdev->dev, &dm355evm_rtc_ops, THIS_MODULE);
	131	+ if (IS_ERR(rtc)) {
	132	+ dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
	133	+ PTR_ERR(rtc));
	134	+ return PTR_ERR(rtc);
	135	+ }
	136	+ platform_set_drvdata(pdev, rtc);
	137	+
	138	+ return 0;
	139	+}
	140	+
	141	+static int __devexit dm355evm_rtc_remove(struct platform_device *pdev)
	142	+{
	143	+ struct rtc_device *rtc = platform_get_drvdata(pdev);
	144	+
	145	+ rtc_device_unregister(rtc);
	146	+ platform_set_drvdata(pdev, NULL);
	147	+ return 0;
	148	+}
	149	+
	150	+/*
	151	+ * I2C is used to talk to the MSP430, but this platform device is
	152	+ * exposed by an MFD driver that manages I2C communications.
	153	+ */
	154	+static struct platform_driver rtc_dm355evm_driver = {
	155	+ .probe = dm355evm_rtc_probe,
	156	+ .remove = __devexit_p(dm355evm_rtc_remove),
	157	+ .driver = {
	158	+ .owner = THIS_MODULE,
	159	+ .name = "rtc-dm355evm",
	160	+ },
	161	+};
	162	+
	163	+static int __init dm355evm_rtc_init(void)
	164	+{
	165	+ return platform_driver_register(&rtc_dm355evm_driver);
	166	+}
	167	+module_init(dm355evm_rtc_init);
	168	+
	169	+static void __exit dm355evm_rtc_exit(void)
	170	+{
	171	+ platform_driver_unregister(&rtc_dm355evm_driver);
	172	+}
	173	+module_exit(dm355evm_rtc_exit);
	174	+
	175	+MODULE_LICENSE("GPL");