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linux-next/drivers/rtc/rtc-rk808.c
Julius Werner f076ef44a4 rtc: rk808: Compensate for Rockchip calendar deviation on November 31st 
In A.D. 1582 Pope Gregory XIII found that the existing Julian calendar
insufficiently represented reality, and changed the rules about
calculating leap years to account for this. Similarly, in A.D. 2013
Rockchip hardware engineers found that the new Gregorian calendar still
contained flaws, and that the month of November should be counted up to
31 days instead. Unfortunately it takes a long time for calendar changes
to gain widespread adoption, and just like more than 300 years went by
before the last Protestant nation implemented Greg's proposal, we will
have to wait a while until all religions and operating system kernels
acknowledge the inherent advantages of the Rockchip system. Until then
we need to translate dates read from (and written to) Rockchip hardware
back to the Gregorian format.

This patch works by defining Jan 1st, 2016 as the arbitrary anchor date
on which Rockchip and Gregorian calendars are in sync. From that we can
translate arbitrary later dates back and forth by counting the number
of November/December transitons since the anchor date to determine the
offset between the calendars. We choose this method (rather than trying
to regularly "correct" the date stored in hardware) since it's the only
way to ensure perfect time-keeping even if the system may be shut down
for an unknown number of years. The drawback is that other software
reading the same hardware (e.g. mainboard firmware) must use the same
translation convention (including the same anchor date) to be able to
read and write correct timestamps from/to the RTC.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
2015-12-20 13:39:00 +01:00

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/*
* RTC driver for Rockchip RK808
*
* Copyright (c) 2014, Fuzhou Rockchip Electronics Co., Ltd
*
* Author: Chris Zhong <zyw@rock-chips.com>
* Author: Zhang Qing <zhangqing@rock-chips.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/rtc.h>
#include <linux/bcd.h>
#include <linux/mfd/rk808.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
/* RTC_CTRL_REG bitfields */
#define BIT_RTC_CTRL_REG_STOP_RTC_M BIT(0)
/* RK808 has a shadowed register for saving a "frozen" RTC time.
* When user setting "GET_TIME" to 1, the time will save in this shadowed
* register. If set "READSEL" to 1, user read rtc time register, actually
* get the time of that moment. If we need the real time, clr this bit.
*/
#define BIT_RTC_CTRL_REG_RTC_GET_TIME BIT(6)
#define BIT_RTC_CTRL_REG_RTC_READSEL_M BIT(7)
#define BIT_RTC_INTERRUPTS_REG_IT_ALARM_M BIT(3)
#define RTC_STATUS_MASK 0xFE
#define SECONDS_REG_MSK 0x7F
#define MINUTES_REG_MAK 0x7F
#define HOURS_REG_MSK 0x3F
#define DAYS_REG_MSK 0x3F
#define MONTHS_REG_MSK 0x1F
#define YEARS_REG_MSK 0xFF
#define WEEKS_REG_MSK 0x7
/* REG_SECONDS_REG through REG_YEARS_REG is how many registers? */
#define NUM_TIME_REGS (RK808_WEEKS_REG - RK808_SECONDS_REG + 1)
#define NUM_ALARM_REGS (RK808_ALARM_YEARS_REG - RK808_ALARM_SECONDS_REG + 1)
struct rk808_rtc {
struct rk808 *rk808;
struct rtc_device *rtc;
int irq;
};
/*
* The Rockchip calendar used by the RK808 counts November with 31 days. We use
* these translation functions to convert its dates to/from the Gregorian
* calendar used by the rest of the world. We arbitrarily define Jan 1st, 2016
* as the day when both calendars were in sync, and treat all other dates
* relative to that.
* NOTE: Other system software (e.g. firmware) that reads the same hardware must
* implement this exact same conversion algorithm, with the same anchor date.
*/
static time64_t nov2dec_transitions(struct rtc_time *tm)
{
return (tm->tm_year + 1900) - 2016 + (tm->tm_mon + 1 > 11 ? 1 : 0);
}
static void rockchip_to_gregorian(struct rtc_time *tm)
{
/* If it's Nov 31st, rtc_tm_to_time64() will count that like Dec 1st */
time64_t time = rtc_tm_to_time64(tm);
rtc_time64_to_tm(time + nov2dec_transitions(tm) * 86400, tm);
}
static void gregorian_to_rockchip(struct rtc_time *tm)
{
time64_t extra_days = nov2dec_transitions(tm);
time64_t time = rtc_tm_to_time64(tm);
rtc_time64_to_tm(time - extra_days * 86400, tm);
/* Compensate if we went back over Nov 31st (will work up to 2381) */
if (nov2dec_transitions(tm) < extra_days) {
if (tm->tm_mon + 1 == 11)
tm->tm_mday++; /* This may result in 31! */
else
rtc_time64_to_tm(time - (extra_days - 1) * 86400, tm);
}
}
/* Read current time and date in RTC */
static int rk808_rtc_readtime(struct device *dev, struct rtc_time *tm)
{
struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
struct rk808 *rk808 = rk808_rtc->rk808;
u8 rtc_data[NUM_TIME_REGS];
int ret;
/* Force an update of the shadowed registers right now */
ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
BIT_RTC_CTRL_REG_RTC_GET_TIME,
BIT_RTC_CTRL_REG_RTC_GET_TIME);
if (ret) {
dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
return ret;
}
/*
* After we set the GET_TIME bit, the rtc time can't be read
* immediately. So we should wait up to 31.25 us, about one cycle of
* 32khz. If we clear the GET_TIME bit here, the time of i2c transfer
* certainly more than 31.25us: 16 * 2.5us at 400kHz bus frequency.
*/
ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
BIT_RTC_CTRL_REG_RTC_GET_TIME,
0);
if (ret) {
dev_err(dev, "Failed to update bits rtc_ctrl: %d\n", ret);
return ret;
}
ret = regmap_bulk_read(rk808->regmap, RK808_SECONDS_REG,
rtc_data, NUM_TIME_REGS);
if (ret) {
dev_err(dev, "Failed to bulk read rtc_data: %d\n", ret);
return ret;
}
tm->tm_sec = bcd2bin(rtc_data[0] & SECONDS_REG_MSK);
tm->tm_min = bcd2bin(rtc_data[1] & MINUTES_REG_MAK);
tm->tm_hour = bcd2bin(rtc_data[2] & HOURS_REG_MSK);
tm->tm_mday = bcd2bin(rtc_data[3] & DAYS_REG_MSK);
tm->tm_mon = (bcd2bin(rtc_data[4] & MONTHS_REG_MSK)) - 1;
tm->tm_year = (bcd2bin(rtc_data[5] & YEARS_REG_MSK)) + 100;
tm->tm_wday = bcd2bin(rtc_data[6] & WEEKS_REG_MSK);
rockchip_to_gregorian(tm);
dev_dbg(dev, "RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
tm->tm_wday, tm->tm_hour, tm->tm_min, tm->tm_sec);
return ret;
}
/* Set current time and date in RTC */
static int rk808_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
struct rk808 *rk808 = rk808_rtc->rk808;
u8 rtc_data[NUM_TIME_REGS];
int ret;
dev_dbg(dev, "set RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
tm->tm_wday, tm->tm_hour, tm->tm_min, tm->tm_sec);
gregorian_to_rockchip(tm);
rtc_data[0] = bin2bcd(tm->tm_sec);
rtc_data[1] = bin2bcd(tm->tm_min);
rtc_data[2] = bin2bcd(tm->tm_hour);
rtc_data[3] = bin2bcd(tm->tm_mday);
rtc_data[4] = bin2bcd(tm->tm_mon + 1);
rtc_data[5] = bin2bcd(tm->tm_year - 100);
rtc_data[6] = bin2bcd(tm->tm_wday);
/* Stop RTC while updating the RTC registers */
ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
BIT_RTC_CTRL_REG_STOP_RTC_M,
BIT_RTC_CTRL_REG_STOP_RTC_M);
if (ret) {
dev_err(dev, "Failed to update RTC control: %d\n", ret);
return ret;
}
ret = regmap_bulk_write(rk808->regmap, RK808_SECONDS_REG,
rtc_data, NUM_TIME_REGS);
if (ret) {
dev_err(dev, "Failed to bull write rtc_data: %d\n", ret);
return ret;
}
/* Start RTC again */
ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
BIT_RTC_CTRL_REG_STOP_RTC_M, 0);
if (ret) {
dev_err(dev, "Failed to update RTC control: %d\n", ret);
return ret;
}
return 0;
}
/* Read alarm time and date in RTC */
static int rk808_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
struct rk808 *rk808 = rk808_rtc->rk808;
u8 alrm_data[NUM_ALARM_REGS];
uint32_t int_reg;
int ret;
ret = regmap_bulk_read(rk808->regmap, RK808_ALARM_SECONDS_REG,
alrm_data, NUM_ALARM_REGS);
alrm->time.tm_sec = bcd2bin(alrm_data[0] & SECONDS_REG_MSK);
alrm->time.tm_min = bcd2bin(alrm_data[1] & MINUTES_REG_MAK);
alrm->time.tm_hour = bcd2bin(alrm_data[2] & HOURS_REG_MSK);
alrm->time.tm_mday = bcd2bin(alrm_data[3] & DAYS_REG_MSK);
alrm->time.tm_mon = (bcd2bin(alrm_data[4] & MONTHS_REG_MSK)) - 1;
alrm->time.tm_year = (bcd2bin(alrm_data[5] & YEARS_REG_MSK)) + 100;
rockchip_to_gregorian(&alrm->time);
ret = regmap_read(rk808->regmap, RK808_RTC_INT_REG, &int_reg);
if (ret) {
dev_err(dev, "Failed to read RTC INT REG: %d\n", ret);
return ret;
}
dev_dbg(dev, "alrm read RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
1900 + alrm->time.tm_year, alrm->time.tm_mon + 1,
alrm->time.tm_mday, alrm->time.tm_wday, alrm->time.tm_hour,
alrm->time.tm_min, alrm->time.tm_sec);
alrm->enabled = (int_reg & BIT_RTC_INTERRUPTS_REG_IT_ALARM_M) ? 1 : 0;
return 0;
}
static int rk808_rtc_stop_alarm(struct rk808_rtc *rk808_rtc)
{
struct rk808 *rk808 = rk808_rtc->rk808;
int ret;
ret = regmap_update_bits(rk808->regmap, RK808_RTC_INT_REG,
BIT_RTC_INTERRUPTS_REG_IT_ALARM_M, 0);
return ret;
}
static int rk808_rtc_start_alarm(struct rk808_rtc *rk808_rtc)
{
struct rk808 *rk808 = rk808_rtc->rk808;
int ret;
ret = regmap_update_bits(rk808->regmap, RK808_RTC_INT_REG,
BIT_RTC_INTERRUPTS_REG_IT_ALARM_M,
BIT_RTC_INTERRUPTS_REG_IT_ALARM_M);
return ret;
}
static int rk808_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
struct rk808 *rk808 = rk808_rtc->rk808;
u8 alrm_data[NUM_ALARM_REGS];
int ret;
ret = rk808_rtc_stop_alarm(rk808_rtc);
if (ret) {
dev_err(dev, "Failed to stop alarm: %d\n", ret);
return ret;
}
dev_dbg(dev, "alrm set RTC date/time %4d-%02d-%02d(%d) %02d:%02d:%02d\n",
1900 + alrm->time.tm_year, alrm->time.tm_mon + 1,
alrm->time.tm_mday, alrm->time.tm_wday, alrm->time.tm_hour,
alrm->time.tm_min, alrm->time.tm_sec);
gregorian_to_rockchip(&alrm->time);
alrm_data[0] = bin2bcd(alrm->time.tm_sec);
alrm_data[1] = bin2bcd(alrm->time.tm_min);
alrm_data[2] = bin2bcd(alrm->time.tm_hour);
alrm_data[3] = bin2bcd(alrm->time.tm_mday);
alrm_data[4] = bin2bcd(alrm->time.tm_mon + 1);
alrm_data[5] = bin2bcd(alrm->time.tm_year - 100);
ret = regmap_bulk_write(rk808->regmap, RK808_ALARM_SECONDS_REG,
alrm_data, NUM_ALARM_REGS);
if (ret) {
dev_err(dev, "Failed to bulk write: %d\n", ret);
return ret;
}
if (alrm->enabled) {
ret = rk808_rtc_start_alarm(rk808_rtc);
if (ret) {
dev_err(dev, "Failed to start alarm: %d\n", ret);
return ret;
}
}
return 0;
}
static int rk808_rtc_alarm_irq_enable(struct device *dev,
unsigned int enabled)
{
struct rk808_rtc *rk808_rtc = dev_get_drvdata(dev);
if (enabled)
return rk808_rtc_start_alarm(rk808_rtc);
return rk808_rtc_stop_alarm(rk808_rtc);
}
/*
* We will just handle setting the frequency and make use the framework for
* reading the periodic interupts.
*
* @freq: Current periodic IRQ freq:
* bit 0: every second
* bit 1: every minute
* bit 2: every hour
* bit 3: every day
*/
static irqreturn_t rk808_alarm_irq(int irq, void *data)
{
struct rk808_rtc *rk808_rtc = data;
struct rk808 *rk808 = rk808_rtc->rk808;
struct i2c_client *client = rk808->i2c;
int ret;
ret = regmap_write(rk808->regmap, RK808_RTC_STATUS_REG,
RTC_STATUS_MASK);
if (ret) {
dev_err(&client->dev,
"%s:Failed to update RTC status: %d\n", __func__, ret);
return ret;
}
rtc_update_irq(rk808_rtc->rtc, 1, RTC_IRQF | RTC_AF);
dev_dbg(&client->dev,
"%s:irq=%d\n", __func__, irq);
return IRQ_HANDLED;
}
static const struct rtc_class_ops rk808_rtc_ops = {
.read_time = rk808_rtc_readtime,
.set_time = rk808_rtc_set_time,
.read_alarm = rk808_rtc_readalarm,
.set_alarm = rk808_rtc_setalarm,
.alarm_irq_enable = rk808_rtc_alarm_irq_enable,
};
#ifdef CONFIG_PM_SLEEP
/* Turn off the alarm if it should not be a wake source. */
static int rk808_rtc_suspend(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct rk808_rtc *rk808_rtc = dev_get_drvdata(&pdev->dev);
if (device_may_wakeup(dev))
enable_irq_wake(rk808_rtc->irq);
return 0;
}
/* Enable the alarm if it should be enabled (in case it was disabled to
* prevent use as a wake source).
*/
static int rk808_rtc_resume(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct rk808_rtc *rk808_rtc = dev_get_drvdata(&pdev->dev);
if (device_may_wakeup(dev))
disable_irq_wake(rk808_rtc->irq);
return 0;
}
#endif
static SIMPLE_DEV_PM_OPS(rk808_rtc_pm_ops,
rk808_rtc_suspend, rk808_rtc_resume);
static int rk808_rtc_probe(struct platform_device *pdev)
{
struct rk808 *rk808 = dev_get_drvdata(pdev->dev.parent);
struct rk808_rtc *rk808_rtc;
struct rtc_time tm;
int ret;
rk808_rtc = devm_kzalloc(&pdev->dev, sizeof(*rk808_rtc), GFP_KERNEL);
if (rk808_rtc == NULL)
return -ENOMEM;
platform_set_drvdata(pdev, rk808_rtc);
rk808_rtc->rk808 = rk808;
/* start rtc running by default, and use shadowed timer. */
ret = regmap_update_bits(rk808->regmap, RK808_RTC_CTRL_REG,
BIT_RTC_CTRL_REG_STOP_RTC_M |
BIT_RTC_CTRL_REG_RTC_READSEL_M,
BIT_RTC_CTRL_REG_RTC_READSEL_M);
if (ret) {
dev_err(&pdev->dev,
"Failed to update RTC control: %d\n", ret);
return ret;
}
ret = regmap_write(rk808->regmap, RK808_RTC_STATUS_REG,
RTC_STATUS_MASK);
if (ret) {
dev_err(&pdev->dev,
"Failed to write RTC status: %d\n", ret);
return ret;
}
/* set init time */
ret = rk808_rtc_readtime(&pdev->dev, &tm);
if (ret) {
dev_err(&pdev->dev, "Failed to read RTC time\n");
return ret;
}
ret = rtc_valid_tm(&tm);
if (ret)
dev_warn(&pdev->dev, "invalid date/time\n");
device_init_wakeup(&pdev->dev, 1);
rk808_rtc->rtc = devm_rtc_device_register(&pdev->dev, "rk808-rtc",
&rk808_rtc_ops, THIS_MODULE);
if (IS_ERR(rk808_rtc->rtc)) {
ret = PTR_ERR(rk808_rtc->rtc);
return ret;
}
rk808_rtc->irq = platform_get_irq(pdev, 0);
if (rk808_rtc->irq < 0) {
if (rk808_rtc->irq != -EPROBE_DEFER)
dev_err(&pdev->dev, "Wake up is not possible as irq = %d\n",
rk808_rtc->irq);
return rk808_rtc->irq;
}
/* request alarm irq of rk808 */
ret = devm_request_threaded_irq(&pdev->dev, rk808_rtc->irq, NULL,
rk808_alarm_irq, 0,
"RTC alarm", rk808_rtc);
if (ret) {
dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
rk808_rtc->irq, ret);
}
return ret;
}
static struct platform_driver rk808_rtc_driver = {
.probe = rk808_rtc_probe,
.driver = {
.name = "rk808-rtc",
.pm = &rk808_rtc_pm_ops,
},
};
module_platform_driver(rk808_rtc_driver);
MODULE_DESCRIPTION("RTC driver for the rk808 series PMICs");
MODULE_AUTHOR("Chris Zhong <zyw@rock-chips.com>");
MODULE_AUTHOR("Zhang Qing <zhangqing@rock-chips.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:rk808-rtc");
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