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linux/drivers/rtc/rtc-wm831x.c
Mark Brown 9dccf55f4c rtc: wm831x: Feed the write counter into device_add_randomness() 
The tamper evident features of the RTC include the "write counter" which
is a pseudo-random number regenerated whenever we set the RTC. Since this
value is unpredictable it should provide some useful seeding to the random
number generator.

Only do this on boot since the goal is to seed the pool rather than add
useful entropy.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
2012-07-19 10:38:31 -04:00

499 lines
13 KiB
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/*
* Real Time Clock driver for Wolfson Microelectronics WM831x
*
* Copyright (C) 2009 Wolfson Microelectronics PLC.
*
* Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
*
* 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/module.h>
#include <linux/kernel.h>
#include <linux/time.h>
#include <linux/rtc.h>
#include <linux/slab.h>
#include <linux/bcd.h>
#include <linux/interrupt.h>
#include <linux/ioctl.h>
#include <linux/completion.h>
#include <linux/mfd/wm831x/core.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/random.h>
/*
* R16416 (0x4020) - RTC Write Counter
*/
#define WM831X_RTC_WR_CNT_MASK 0xFFFF /* RTC_WR_CNT - [15:0] */
#define WM831X_RTC_WR_CNT_SHIFT 0 /* RTC_WR_CNT - [15:0] */
#define WM831X_RTC_WR_CNT_WIDTH 16 /* RTC_WR_CNT - [15:0] */
/*
* R16417 (0x4021) - RTC Time 1
*/
#define WM831X_RTC_TIME_MASK 0xFFFF /* RTC_TIME - [15:0] */
#define WM831X_RTC_TIME_SHIFT 0 /* RTC_TIME - [15:0] */
#define WM831X_RTC_TIME_WIDTH 16 /* RTC_TIME - [15:0] */
/*
* R16418 (0x4022) - RTC Time 2
*/
#define WM831X_RTC_TIME_MASK 0xFFFF /* RTC_TIME - [15:0] */
#define WM831X_RTC_TIME_SHIFT 0 /* RTC_TIME - [15:0] */
#define WM831X_RTC_TIME_WIDTH 16 /* RTC_TIME - [15:0] */
/*
* R16419 (0x4023) - RTC Alarm 1
*/
#define WM831X_RTC_ALM_MASK 0xFFFF /* RTC_ALM - [15:0] */
#define WM831X_RTC_ALM_SHIFT 0 /* RTC_ALM - [15:0] */
#define WM831X_RTC_ALM_WIDTH 16 /* RTC_ALM - [15:0] */
/*
* R16420 (0x4024) - RTC Alarm 2
*/
#define WM831X_RTC_ALM_MASK 0xFFFF /* RTC_ALM - [15:0] */
#define WM831X_RTC_ALM_SHIFT 0 /* RTC_ALM - [15:0] */
#define WM831X_RTC_ALM_WIDTH 16 /* RTC_ALM - [15:0] */
/*
* R16421 (0x4025) - RTC Control
*/
#define WM831X_RTC_VALID 0x8000 /* RTC_VALID */
#define WM831X_RTC_VALID_MASK 0x8000 /* RTC_VALID */
#define WM831X_RTC_VALID_SHIFT 15 /* RTC_VALID */
#define WM831X_RTC_VALID_WIDTH 1 /* RTC_VALID */
#define WM831X_RTC_SYNC_BUSY 0x4000 /* RTC_SYNC_BUSY */
#define WM831X_RTC_SYNC_BUSY_MASK 0x4000 /* RTC_SYNC_BUSY */
#define WM831X_RTC_SYNC_BUSY_SHIFT 14 /* RTC_SYNC_BUSY */
#define WM831X_RTC_SYNC_BUSY_WIDTH 1 /* RTC_SYNC_BUSY */
#define WM831X_RTC_ALM_ENA 0x0400 /* RTC_ALM_ENA */
#define WM831X_RTC_ALM_ENA_MASK 0x0400 /* RTC_ALM_ENA */
#define WM831X_RTC_ALM_ENA_SHIFT 10 /* RTC_ALM_ENA */
#define WM831X_RTC_ALM_ENA_WIDTH 1 /* RTC_ALM_ENA */
#define WM831X_RTC_PINT_FREQ_MASK 0x0070 /* RTC_PINT_FREQ - [6:4] */
#define WM831X_RTC_PINT_FREQ_SHIFT 4 /* RTC_PINT_FREQ - [6:4] */
#define WM831X_RTC_PINT_FREQ_WIDTH 3 /* RTC_PINT_FREQ - [6:4] */
/*
* R16422 (0x4026) - RTC Trim
*/
#define WM831X_RTC_TRIM_MASK 0x03FF /* RTC_TRIM - [9:0] */
#define WM831X_RTC_TRIM_SHIFT 0 /* RTC_TRIM - [9:0] */
#define WM831X_RTC_TRIM_WIDTH 10 /* RTC_TRIM - [9:0] */
#define WM831X_SET_TIME_RETRIES 5
#define WM831X_GET_TIME_RETRIES 5
struct wm831x_rtc {
struct wm831x *wm831x;
struct rtc_device *rtc;
unsigned int alarm_enabled:1;
};
static void wm831x_rtc_add_randomness(struct wm831x *wm831x)
{
int ret;
u16 reg;
/*
* The write counter contains a pseudo-random number which is
* regenerated every time we set the RTC so it should be a
* useful per-system source of entropy.
*/
ret = wm831x_reg_read(wm831x, WM831X_RTC_WRITE_COUNTER);
if (ret >= 0) {
reg = ret;
add_device_randomness(&reg, sizeof(reg));
} else {
dev_warn(wm831x->dev, "Failed to read RTC write counter: %d\n",
ret);
}
}
/*
* Read current time and date in RTC
*/
static int wm831x_rtc_readtime(struct device *dev, struct rtc_time *tm)
{
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
struct wm831x *wm831x = wm831x_rtc->wm831x;
u16 time1[2], time2[2];
int ret;
int count = 0;
/* Has the RTC been programmed? */
ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
if (ret < 0) {
dev_err(dev, "Failed to read RTC control: %d\n", ret);
return ret;
}
if (!(ret & WM831X_RTC_VALID)) {
dev_dbg(dev, "RTC not yet configured\n");
return -EINVAL;
}
/* Read twice to make sure we don't read a corrupt, partially
* incremented, value.
*/
do {
ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
2, time1);
if (ret != 0)
continue;
ret = wm831x_bulk_read(wm831x, WM831X_RTC_TIME_1,
2, time2);
if (ret != 0)
continue;
if (memcmp(time1, time2, sizeof(time1)) == 0) {
u32 time = (time1[0] << 16) | time1[1];
rtc_time_to_tm(time, tm);
return rtc_valid_tm(tm);
}
} while (++count < WM831X_GET_TIME_RETRIES);
dev_err(dev, "Timed out reading current time\n");
return -EIO;
}
/*
* Set current time and date in RTC
*/
static int wm831x_rtc_set_mmss(struct device *dev, unsigned long time)
{
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
struct wm831x *wm831x = wm831x_rtc->wm831x;
struct rtc_time new_tm;
unsigned long new_time;
int ret;
int count = 0;
ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_1,
(time >> 16) & 0xffff);
if (ret < 0) {
dev_err(dev, "Failed to write TIME_1: %d\n", ret);
return ret;
}
ret = wm831x_reg_write(wm831x, WM831X_RTC_TIME_2, time & 0xffff);
if (ret < 0) {
dev_err(dev, "Failed to write TIME_2: %d\n", ret);
return ret;
}
/* Wait for the update to complete - should happen first time
* round but be conservative.
*/
do {
msleep(1);
ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
if (ret < 0)
ret = WM831X_RTC_SYNC_BUSY;
} while (!(ret & WM831X_RTC_SYNC_BUSY) &&
++count < WM831X_SET_TIME_RETRIES);
if (ret & WM831X_RTC_SYNC_BUSY) {
dev_err(dev, "Timed out writing RTC update\n");
return -EIO;
}
/* Check that the update was accepted; security features may
* have caused the update to be ignored.
*/
ret = wm831x_rtc_readtime(dev, &new_tm);
if (ret < 0)
return ret;
ret = rtc_tm_to_time(&new_tm, &new_time);
if (ret < 0) {
dev_err(dev, "Failed to convert time: %d\n", ret);
return ret;
}
/* Allow a second of change in case of tick */
if (new_time - time > 1) {
dev_err(dev, "RTC update not permitted by hardware\n");
return -EPERM;
}
return 0;
}
/*
* Read alarm time and date in RTC
*/
static int wm831x_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
int ret;
u16 data[2];
u32 time;
ret = wm831x_bulk_read(wm831x_rtc->wm831x, WM831X_RTC_ALARM_1,
2, data);
if (ret != 0) {
dev_err(dev, "Failed to read alarm time: %d\n", ret);
return ret;
}
time = (data[0] << 16) | data[1];
rtc_time_to_tm(time, &alrm->time);
ret = wm831x_reg_read(wm831x_rtc->wm831x, WM831X_RTC_CONTROL);
if (ret < 0) {
dev_err(dev, "Failed to read RTC control: %d\n", ret);
return ret;
}
if (ret & WM831X_RTC_ALM_ENA)
alrm->enabled = 1;
else
alrm->enabled = 0;
return 0;
}
static int wm831x_rtc_stop_alarm(struct wm831x_rtc *wm831x_rtc)
{
wm831x_rtc->alarm_enabled = 0;
return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
WM831X_RTC_ALM_ENA, 0);
}
static int wm831x_rtc_start_alarm(struct wm831x_rtc *wm831x_rtc)
{
wm831x_rtc->alarm_enabled = 1;
return wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
WM831X_RTC_ALM_ENA, WM831X_RTC_ALM_ENA);
}
static int wm831x_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
struct wm831x *wm831x = wm831x_rtc->wm831x;
int ret;
unsigned long time;
ret = rtc_tm_to_time(&alrm->time, &time);
if (ret < 0) {
dev_err(dev, "Failed to convert time: %d\n", ret);
return ret;
}
ret = wm831x_rtc_stop_alarm(wm831x_rtc);
if (ret < 0) {
dev_err(dev, "Failed to stop alarm: %d\n", ret);
return ret;
}
ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_1,
(time >> 16) & 0xffff);
if (ret < 0) {
dev_err(dev, "Failed to write ALARM_1: %d\n", ret);
return ret;
}
ret = wm831x_reg_write(wm831x, WM831X_RTC_ALARM_2, time & 0xffff);
if (ret < 0) {
dev_err(dev, "Failed to write ALARM_2: %d\n", ret);
return ret;
}
if (alrm->enabled) {
ret = wm831x_rtc_start_alarm(wm831x_rtc);
if (ret < 0) {
dev_err(dev, "Failed to start alarm: %d\n", ret);
return ret;
}
}
return 0;
}
static int wm831x_rtc_alarm_irq_enable(struct device *dev,
unsigned int enabled)
{
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(dev);
if (enabled)
return wm831x_rtc_start_alarm(wm831x_rtc);
else
return wm831x_rtc_stop_alarm(wm831x_rtc);
}
static irqreturn_t wm831x_alm_irq(int irq, void *data)
{
struct wm831x_rtc *wm831x_rtc = data;
rtc_update_irq(wm831x_rtc->rtc, 1, RTC_IRQF | RTC_AF);
return IRQ_HANDLED;
}
static const struct rtc_class_ops wm831x_rtc_ops = {
.read_time = wm831x_rtc_readtime,
.set_mmss = wm831x_rtc_set_mmss,
.read_alarm = wm831x_rtc_readalarm,
.set_alarm = wm831x_rtc_setalarm,
.alarm_irq_enable = wm831x_rtc_alarm_irq_enable,
};
#ifdef CONFIG_PM
/* Turn off the alarm if it should not be a wake source. */
static int wm831x_rtc_suspend(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(&pdev->dev);
int ret, enable;
if (wm831x_rtc->alarm_enabled && device_may_wakeup(&pdev->dev))
enable = WM831X_RTC_ALM_ENA;
else
enable = 0;
ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
WM831X_RTC_ALM_ENA, enable);
if (ret != 0)
dev_err(&pdev->dev, "Failed to update RTC alarm: %d\n", ret);
return 0;
}
/* Enable the alarm if it should be enabled (in case it was disabled to
* prevent use as a wake source).
*/
static int wm831x_rtc_resume(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(&pdev->dev);
int ret;
if (wm831x_rtc->alarm_enabled) {
ret = wm831x_rtc_start_alarm(wm831x_rtc);
if (ret != 0)
dev_err(&pdev->dev,
"Failed to restart RTC alarm: %d\n", ret);
}
return 0;
}
/* Unconditionally disable the alarm */
static int wm831x_rtc_freeze(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct wm831x_rtc *wm831x_rtc = dev_get_drvdata(&pdev->dev);
int ret;
ret = wm831x_set_bits(wm831x_rtc->wm831x, WM831X_RTC_CONTROL,
WM831X_RTC_ALM_ENA, 0);
if (ret != 0)
dev_err(&pdev->dev, "Failed to stop RTC alarm: %d\n", ret);
return 0;
}
#else
#define wm831x_rtc_suspend NULL
#define wm831x_rtc_resume NULL
#define wm831x_rtc_freeze NULL
#endif
static int wm831x_rtc_probe(struct platform_device *pdev)
{
struct wm831x *wm831x = dev_get_drvdata(pdev->dev.parent);
struct wm831x_rtc *wm831x_rtc;
int alm_irq = wm831x_irq(wm831x, platform_get_irq_byname(pdev, "ALM"));
int ret = 0;
wm831x_rtc = devm_kzalloc(&pdev->dev, sizeof(*wm831x_rtc), GFP_KERNEL);
if (wm831x_rtc == NULL)
return -ENOMEM;
platform_set_drvdata(pdev, wm831x_rtc);
wm831x_rtc->wm831x = wm831x;
ret = wm831x_reg_read(wm831x, WM831X_RTC_CONTROL);
if (ret < 0) {
dev_err(&pdev->dev, "Failed to read RTC control: %d\n", ret);
goto err;
}
if (ret & WM831X_RTC_ALM_ENA)
wm831x_rtc->alarm_enabled = 1;
device_init_wakeup(&pdev->dev, 1);
wm831x_rtc->rtc = rtc_device_register("wm831x", &pdev->dev,
&wm831x_rtc_ops, THIS_MODULE);
if (IS_ERR(wm831x_rtc->rtc)) {
ret = PTR_ERR(wm831x_rtc->rtc);
goto err;
}
ret = request_threaded_irq(alm_irq, NULL, wm831x_alm_irq,
IRQF_TRIGGER_RISING, "RTC alarm",
wm831x_rtc);
if (ret != 0) {
dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
alm_irq, ret);
}
wm831x_rtc_add_randomness(wm831x);
return 0;
err:
return ret;
}
static int __devexit wm831x_rtc_remove(struct platform_device *pdev)
{
struct wm831x_rtc *wm831x_rtc = platform_get_drvdata(pdev);
int alm_irq = platform_get_irq_byname(pdev, "ALM");
free_irq(alm_irq, wm831x_rtc);
rtc_device_unregister(wm831x_rtc->rtc);
return 0;
}
static const struct dev_pm_ops wm831x_rtc_pm_ops = {
.suspend = wm831x_rtc_suspend,
.resume = wm831x_rtc_resume,
.freeze = wm831x_rtc_freeze,
.thaw = wm831x_rtc_resume,
.restore = wm831x_rtc_resume,
.poweroff = wm831x_rtc_suspend,
};
static struct platform_driver wm831x_rtc_driver = {
.probe = wm831x_rtc_probe,
.remove = __devexit_p(wm831x_rtc_remove),
.driver = {
.name = "wm831x-rtc",
.pm = &wm831x_rtc_pm_ops,
},
};
module_platform_driver(wm831x_rtc_driver);
MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
MODULE_DESCRIPTION("RTC driver for the WM831x series PMICs");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:wm831x-rtc");
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