[PATCH 8/8] rtc: st: add new driver for ST's LPC RTC

Lee Jones
2014-12-17T16:46:04Z

ST's Low Power Controller (LPC) controls two devices; watchdog and RTC.
Only one of the devices can be used at any one time. This is enforced
by the correlating MFD driver. This portion of the driver-set controls
the Real Time Clock.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/rtc/Kconfig | 13 ++
drivers/rtc/Makefile | 1 +
drivers/rtc/rtc-st-lpc.c | 354 ++++++++++++++++++++++++++++++++++++++++++++++
drivers/watchdog/st_wdt.c | 8 +-
4 files changed, 375 insertions(+), 1 deletion(-)
create mode 100644 drivers/rtc/rtc-st-lpc.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index a168e96..aa4bd90 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1355,6 +1355,18 @@ config RTC_DRV_SIRFSOC
Say "yes" here to support the real time clock on SiRF SOC chips.
This driver can also be built as a module called rtc-sirfsoc.

+config RTC_DRV_ST_LPC
+ tristate "STMicroelectronics LPC RTC"
+ depends on ARCH_STI
+ depends on OF
+ select MFD_ST_LPC
+ help
+ Say Y here to include STMicroelectronics Low Power Controller
+ (LPC) based RTC support.
+
+ To compile this driver as a module, choose M here: the
+ module will be called rtc-st-lpc.
+
config RTC_DRV_MOXART
tristate "MOXA ART RTC"
depends on ARCH_MOXART || COMPILE_TEST
@@ -1390,4 +1402,5 @@ config RTC_DRV_HID_SENSOR_TIME
rtc-hid-sensor-time.

+
endif # RTC_CLASS
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 56f061c..ce5860b 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -145,4 +145,5 @@ obj-$(CONFIG_RTC_DRV_WM8350) += rtc-wm8350.o
obj-$(CONFIG_RTC_DRV_X1205) += rtc-x1205.o
obj-$(CONFIG_RTC_DRV_XGENE) += rtc-xgene.o
obj-$(CONFIG_RTC_DRV_SIRFSOC) += rtc-sirfsoc.o
+obj-$(CONFIG_RTC_DRV_ST_LPC) += rtc-st-lpc.o
obj-$(CONFIG_RTC_DRV_MOXART) += rtc-moxart.o
diff --git a/drivers/rtc/rtc-st-lpc.c b/drivers/rtc/rtc-st-lpc.c
new file mode 100644
index 0000000..de28aca
--- /dev/null
+++ b/drivers/rtc/rtc-st-lpc.c
@@ -0,0 +1,354 @@
+/*
+ * rtc-st-lpc.c - ST's LPC RTC, powered by the Low Power Timer
+ *
+ * Copyright (C) 2014 STMicroelectronics Limited
+ *
+ * Author: David Paris <david.paris@st.com> for STMicroelectronics
+ * Lee Jones <lee.jones@linaro.org> for STMicroelectronics
+ *
+ * Based on the original driver written by Stuart Menefy.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+#include <dt-bindings/mfd/st-lpc.h>
+
+/* Low Power Timer */
+#define LPC_LPT_LSB_OFF 0x400
+#define LPC_LPT_MSB_OFF 0x404
+#define LPC_LPT_START_OFF 0x408
+
+/* Low Power Alarm */
+#define LPC_LPA_LSB_OFF 0x410
+#define LPC_LPA_MSB_OFF 0x414
+#define LPC_LPA_START_OFF 0x418
+
+/* LPC as WDT */
+#define LPC_WDT_OFF 0x510
+#define LPC_WDT_FLAG_OFF 0x514
+
+struct st_rtc {
+ struct rtc_device *rtc_dev;
+ struct rtc_wkalrm alarm;
+ struct resource *res;
+ struct clk *clk;
+ unsigned long clkrate;
+ void __iomem *ioaddr;
+ bool irq_enabled:1;
+ spinlock_t lock;
+ short irq;
+};
+
+static void st_rtc_set_hw_alarm(struct st_rtc *rtc,
+ unsigned long msb, unsigned long lsb)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&rtc->lock, flags);
+
+ writel(1, rtc->ioaddr + LPC_WDT_OFF);
+
+ writel(msb, rtc->ioaddr + LPC_LPA_MSB_OFF);
+ writel(lsb, rtc->ioaddr + LPC_LPA_LSB_OFF);
+ writel(1, rtc->ioaddr + LPC_LPA_START_OFF);
+
+ writel(0, rtc->ioaddr + LPC_WDT_OFF);
+
+ spin_unlock_irqrestore(&rtc->lock, flags);
+}
+
+static irqreturn_t st_rtc_handler(int this_irq, void *data)
+{
+ struct st_rtc *rtc = (struct st_rtc *)data;
+
+ rtc_update_irq(rtc->rtc_dev, 1, RTC_AF);
+
+ return IRQ_HANDLED;
+}
+
+static int st_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+ unsigned long lpt_lsb, lpt_msb;
+ unsigned long long lpt;
+ unsigned long flags;
+
+ spin_lock_irqsave(&rtc->lock, flags);
+
+ do {
+ lpt_msb = readl(rtc->ioaddr + LPC_LPT_MSB_OFF);
+ lpt_lsb = readl(rtc->ioaddr + LPC_LPT_LSB_OFF);
+ } while (readl(rtc->ioaddr + LPC_LPT_MSB_OFF) != lpt_msb);
+
+ spin_unlock_irqrestore(&rtc->lock, flags);
+
+ lpt = ((unsigned long long)lpt_msb << 32) | lpt_lsb;
+ do_div(lpt, rtc->clkrate);
+ rtc_time_to_tm(lpt, tm);
+
+ return 0;
+}
+
+static int st_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+ unsigned long long lpt;
+ unsigned long secs, flags;
+ int ret;
+
+ ret = rtc_tm_to_time(tm, &secs);
+ if (ret)
+ return ret;
+
+ lpt = (unsigned long long)secs * rtc->clkrate;
+
+ spin_lock_irqsave(&rtc->lock, flags);
+
+ writel(lpt >> 32, rtc->ioaddr + LPC_LPT_MSB_OFF);
+ writel(lpt, rtc->ioaddr + LPC_LPT_LSB_OFF);
+ writel(1, rtc->ioaddr + LPC_LPT_START_OFF);
+
+ spin_unlock_irqrestore(&rtc->lock, flags);
+
+ return 0;
+}
+
+static int st_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+ unsigned long flags;
+
+ spin_lock_irqsave(&rtc->lock, flags);
+
+ memcpy(wkalrm, &rtc->alarm, sizeof(struct rtc_wkalrm));
+
+ spin_unlock_irqrestore(&rtc->lock, flags);
+
+ return 0;
+}
+
+static int st_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+
+ if (enabled && !rtc->irq_enabled) {
+ enable_irq(rtc->irq);
+ rtc->irq_enabled = true;
+ } else if (!enabled && rtc->irq_enabled) {
+ disable_irq(rtc->irq);
+ rtc->irq_enabled = false;
+ }
+
+ return 0;
+}
+
+static int st_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+ struct rtc_time now;
+ unsigned long now_secs;
+ unsigned long alarm_secs;
+ unsigned long long lpa;
+
+ st_rtc_read_time(dev, &now);
+ rtc_tm_to_time(&now, &now_secs);
+ rtc_tm_to_time(&t->time, &alarm_secs);
+
+ /* Invalid alarm time */
+ if (now_secs > alarm_secs)
+ return -EINVAL;
+
+ memcpy(&rtc->alarm, t, sizeof(struct rtc_wkalrm));
+
+ /* Now many secs to fire */
+ alarm_secs -= now_secs;
+ lpa = (unsigned long long)alarm_secs * rtc->clkrate;
+
+ st_rtc_set_hw_alarm(rtc, lpa >> 32, lpa);
+ st_rtc_alarm_irq_enable(dev, t->enabled);
+
+ return 0;
+}
+
+static struct rtc_class_ops st_rtc_ops = {
+ .read_time = st_rtc_read_time,
+ .set_time = st_rtc_set_time,
+ .read_alarm = st_rtc_read_alarm,
+ .set_alarm = st_rtc_set_alarm,
+ .alarm_irq_enable = st_rtc_alarm_irq_enable,
+};
+
+static int st_rtc_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct st_rtc *rtc;
+ struct resource *res;
+ struct rtc_time tm_check;
+ uint32_t mode;
+ int ret = 0;
+
+ ret = of_property_read_u32(np, "st,lpc-mode", &mode);
+ if (ret) {
+ dev_err(&pdev->dev, "An LPC mode must be provided\n");
+ return -EINVAL;
+ }
+
+ /* LPC can either run in RTC or WDT mode */
+ if (mode != ST_LPC_MODE_RTC)
+ return -ENODEV;
+
+ rtc = devm_kzalloc(&pdev->dev, sizeof(struct st_rtc), GFP_KERNEL);
+ if (!rtc)
+ return -ENOMEM;
+
+ spin_lock_init(&rtc->lock);
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ rtc->ioaddr = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(rtc->ioaddr))
+ return PTR_ERR(rtc->ioaddr);
+
+ rtc->irq = irq_of_parse_and_map(np, 0);
+ if (!rtc->irq) {
+ dev_err(&pdev->dev, "IRQ missing or invalid\n");
+ return -EINVAL;
+ }
+
+ ret = devm_request_irq(&pdev->dev, rtc->irq, st_rtc_handler, 0,
+ pdev->name, rtc);
+ if (ret) {
+ dev_err(&pdev->dev, "Failed to request irq %i\n", rtc->irq);
+ return ret;
+ }
+
+ enable_irq_wake(rtc->irq);
+ disable_irq(rtc->irq);
+
+ rtc->clk = clk_get(&pdev->dev, NULL);
+ if (IS_ERR(rtc->clk)) {
+ dev_err(&pdev->dev, "Unable to request clock\n");
+ return PTR_ERR(rtc->clk);
+ }
+
+ clk_prepare_enable(rtc->clk);
+
+ rtc->clkrate = clk_get_rate(rtc->clk);
+ if (!rtc->clkrate) {
+ dev_err(&pdev->dev, "Unable to fetch clock rate\n");
+ return -EINVAL;
+ }
+
+ device_set_wakeup_capable(&pdev->dev, 1);
+
+ platform_set_drvdata(pdev, rtc);
+
+ /*
+ * The RTC-LPC is able to manage date.year > 2038
+ * but currently the kernel can not manage this date!
+ * If the RTC-LPC has a date.year > 2038 then
+ * it's set to the epoch "Jan 1st 2000"
+ */
+ st_rtc_read_time(&pdev->dev, &tm_check);
+
+ if (tm_check.tm_year >= (2038 - 1900)) {
+ memset(&tm_check, 0, sizeof(tm_check));
+ tm_check.tm_year = 100;
+ tm_check.tm_mday = 1;
+ st_rtc_set_time(&pdev->dev, &tm_check);
+ }
+
+ rtc->rtc_dev = rtc_device_register("st-lpc-rtc", &pdev->dev,
+ &st_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc->rtc_dev)) {
+ clk_disable_unprepare(rtc->clk);
+ return PTR_ERR(rtc->rtc_dev);
+ }
+
+ return 0;
+}
+
+static int st_rtc_remove(struct platform_device *pdev)
+{
+ struct st_rtc *rtc = platform_get_drvdata(pdev);
+
+ if (likely(rtc->rtc_dev))
+ rtc_device_unregister(rtc->rtc_dev);
+
+ return 0;
+}
+
+#ifdef CONFIG_PM
+static int st_rtc_suspend(struct device *dev)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+
+ if (device_may_wakeup(dev))
+ return 0;
+
+ writel(1, rtc->ioaddr + LPC_WDT_OFF);
+ writel(0, rtc->ioaddr + LPC_LPA_START_OFF);
+ writel(0, rtc->ioaddr + LPC_WDT_OFF);
+
+ return 0;
+}
+
+static int st_rtc_resume(struct device *dev)
+{
+ struct st_rtc *rtc = dev_get_drvdata(dev);
+
+ rtc_alarm_irq_enable(rtc->rtc_dev, 0);
+
+ /*
+ * clean 'rtc->alarm' to allow a new
+ * .set_alarm to the upper RTC layer
+ */
+ memset(&rtc->alarm, 0, sizeof(struct rtc_wkalrm));
+
+ writel(0, rtc->ioaddr + LPC_LPA_MSB_OFF);
+ writel(0, rtc->ioaddr + LPC_LPA_LSB_OFF);
+ writel(1, rtc->ioaddr + LPC_WDT_OFF);
+ writel(1, rtc->ioaddr + LPC_LPA_START_OFF);
+ writel(0, rtc->ioaddr + LPC_WDT_OFF);
+
+ return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(st_rtc_pm_ops, st_rtc_suspend, st_rtc_resume);
+
+static struct of_device_id st_rtc_match[] = {
+ { .compatible = "st,stih407-lpc" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, st_wdog_match);
+
+static struct platform_driver st_rtc_platform_driver = {
+ .driver = {
+ .name = "st-lpc-rtc",
+ .pm = &st_rtc_pm_ops,
+ .of_match_table = st_rtc_match,
+ },
+ .probe = st_rtc_probe,
+ .remove = st_rtc_remove,
+};
+
+module_platform_driver(st_rtc_platform_driver);
+
+MODULE_DESCRIPTION("STMicroelectronics LPC RTC driver");
+MODULE_AUTHOR("David Paris <david.paris@st.com>");
+MODULE_LICENSE("GPLv2");
diff --git a/drivers/watchdog/st_wdt.c b/drivers/watchdog/st_wdt.c
index cf3a4f7..166b57c 100644
--- a/drivers/watchdog/st_wdt.c
+++ b/drivers/watchdog/st_wdt.c
@@ -281,12 +281,16 @@ static int st_wdog_remove(struct platform_device *pdev)
return 0;
}

-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
static int st_wdog_suspend(struct device *dev)
{
+ struct st_wdog *st_wdog = watchdog_get_drvdata(&st_wdog_dev);
+
if (watchdog_active(&st_wdog_dev))
st_wdog_stop(&st_wdog_dev);

+ st_wdog_setup(st_wdog, false);
+
return 0;
}

@@ -294,6 +298,8 @@ static int st_wdog_resume(struct device *dev)
{
struct st_wdog *st_wdog = watchdog_get_drvdata(&st_wdog_dev);

+ st_wdog_setup(st_wdog, true);
+
if (watchdog_active(&st_wdog_dev)) {
st_wdog_load_timer(st_wdog, st_wdog_dev.timeout);
st_wdog_start(&st_wdog_dev);
--
1.9.1