diff options
author | David Brownell <dbrownell@users.sourceforge.net> | 2009-02-04 23:12:01 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-02-05 20:56:46 (GMT) |
commit | afd8d0f940ba5078f38e435440089117ac7d9eb4 (patch) | |
tree | 1f494035691b04175ed21ed3703593ce37957925 /drivers/rtc | |
parent | 77a592655cdb8d838b85fd7ecf8f36fd2870abfc (diff) | |
download | linux-afd8d0f940ba5078f38e435440089117ac7d9eb4.tar.xz |
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>
Diffstat (limited to 'drivers/rtc')
-rw-r--r-- | drivers/rtc/Kconfig | 6 | ||||
-rw-r--r-- | drivers/rtc/Makefile | 1 | ||||
-rw-r--r-- | drivers/rtc/rtc-dm355evm.c | 175 |
3 files changed, 182 insertions, 0 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index cced4d1..81450fb 100644 --- a/drivers/rtc/Kconfig +++ b/drivers/rtc/Kconfig @@ -241,6 +241,12 @@ config RTC_DRV_M41T80_WDT 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 diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile index 6e28021..0e697aa 100644 --- a/drivers/rtc/Makefile +++ b/drivers/rtc/Makefile @@ -23,6 +23,7 @@ obj-$(CONFIG_RTC_DRV_AT91SAM9) += rtc-at91sam9.o obj-$(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 diff --git a/drivers/rtc/rtc-dm355evm.c b/drivers/rtc/rtc-dm355evm.c new file mode 100644 index 0000000..58d4e18 --- /dev/null +++ b/drivers/rtc/rtc-dm355evm.c @@ -0,0 +1,175 @@ +/* + * 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"); |