rtc-au1xxx.c
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/*
* Au1xxx counter0 (aka Time-Of-Year counter) RTC interface driver.
*
* Copyright (C) 2008 Manuel Lauss <mano@roarinelk.homelinux.net>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
/* All current Au1xxx SoCs have 2 counters fed by an external 32.768 kHz
* crystal. Counter 0, which keeps counting during sleep/powerdown, is
* used to count seconds since the beginning of the unix epoch.
*
* The counters must be configured and enabled by bootloader/board code;
* no checks as to whether they really get a proper 32.768kHz clock are
* made as this would take far too long.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/rtc.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <asm/mach-au1x00/au1000.h>
/* 32kHz clock enabled and detected */
#define CNTR_OK (SYS_CNTRL_E0 | SYS_CNTRL_32S)
static int au1xtoy_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
unsigned long t;
t = au_readl(SYS_TOYREAD);
rtc_time_to_tm(t, tm);
return rtc_valid_tm(tm);
}
static int au1xtoy_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
unsigned long t;
rtc_tm_to_time(tm, &t);
au_writel(t, SYS_TOYWRITE);
au_sync();
/* wait for the pending register write to succeed. This can
* take up to 6 seconds...
*/
while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S)
msleep(1);
return 0;
}
static struct rtc_class_ops au1xtoy_rtc_ops = {
.read_time = au1xtoy_rtc_read_time,
.set_time = au1xtoy_rtc_set_time,
};
static int au1xtoy_rtc_probe(struct platform_device *pdev)
{
struct rtc_device *rtcdev;
unsigned long t;
int ret;
t = au_readl(SYS_COUNTER_CNTRL);
if (!(t & CNTR_OK)) {
dev_err(&pdev->dev, "counters not working; aborting.\n");
ret = -ENODEV;
goto out_err;
}
ret = -ETIMEDOUT;
/* set counter0 tickrate to 1Hz if necessary */
if (au_readl(SYS_TOYTRIM) != 32767) {
/* wait until hardware gives access to TRIM register */
t = 0x00100000;
while ((au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_T0S) && --t)
msleep(1);
if (!t) {
/* timed out waiting for register access; assume
* counters are unusable.
*/
dev_err(&pdev->dev, "timeout waiting for access\n");
goto out_err;
}
/* set 1Hz TOY tick rate */
au_writel(32767, SYS_TOYTRIM);
au_sync();
}
/* wait until the hardware allows writes to the counter reg */
while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S)
msleep(1);
rtcdev = devm_rtc_device_register(&pdev->dev, "rtc-au1xxx",
&au1xtoy_rtc_ops, THIS_MODULE);
if (IS_ERR(rtcdev)) {
ret = PTR_ERR(rtcdev);
goto out_err;
}
platform_set_drvdata(pdev, rtcdev);
return 0;
out_err:
return ret;
}
static struct platform_driver au1xrtc_driver = {
.driver = {
.name = "rtc-au1xxx",
.owner = THIS_MODULE,
},
};
module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rtc-au1xxx");