mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-18 17:54:13 +08:00
0929ae376e
A platform_driver does not need to set an owner, it will be populated by the driver core. Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
156 lines
3.8 KiB
C
156 lines
3.8 KiB
C
/*
|
|
* 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>
|
|
#include <linux/module.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 dm355evm_rtc_probe(struct platform_device *pdev)
|
|
{
|
|
struct rtc_device *rtc;
|
|
|
|
rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
|
|
&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;
|
|
}
|
|
|
|
/*
|
|
* 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,
|
|
.driver = {
|
|
.name = "rtc-dm355evm",
|
|
},
|
|
};
|
|
|
|
module_platform_driver(rtc_dm355evm_driver);
|
|
|
|
MODULE_LICENSE("GPL");
|