rtc: fsl-ftm-alarm: add FTM alarm driver

For the platforms including LS1012A, LS1021A, LS1028A, LS1043A,
LS1046A, LS1088A, LS208xA that has the FlexTimer
module, implementing alarm functions within RTC subsystem
to wakeup the system when system going to sleep (work with RCPM driver).

Signed-off-by: Biwen Li <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/Kconfig

···
 	   This driver can also be built as a module, if so, the module
 	   will be called "rtc-imxdi".
 
+config RTC_DRV_FSL_FTM_ALARM
+	tristate "Freescale FlexTimer alarm timer"
+	depends on ARCH_LAYERSCAPE || SOC_LS1021A
+	select FSL_RCPM
+	default y
+	help
+	   For the FlexTimer in LS1012A, LS1021A, LS1028A, LS1043A, LS1046A,
+	   LS1088A, LS208xA, we can use FTM as the wakeup source.
+
+	   Say y here to enable FTM alarm support. The FTM alarm provides
+	   alarm functions for wakeup system from deep sleep.
+
+	   This driver can also be built as a module, if so, the module
+	   will be called "rtc-fsl-ftm-alarm".
+
 config RTC_DRV_MESON
 	tristate "Amlogic Meson RTC"
 	depends on (ARM && ARCH_MESON) || COMPILE_TEST

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_EM3027)	+= rtc-em3027.o
 obj-$(CONFIG_RTC_DRV_EP93XX)	+= rtc-ep93xx.o
 obj-$(CONFIG_RTC_DRV_FM3130)	+= rtc-fm3130.o
+obj-$(CONFIG_RTC_DRV_FSL_FTM_ALARM)	+= rtc-fsl-ftm-alarm.o
 obj-$(CONFIG_RTC_DRV_FTRTC010)	+= rtc-ftrtc010.o
 obj-$(CONFIG_RTC_DRV_GENERIC)	+= rtc-generic.o
 obj-$(CONFIG_RTC_DRV_GOLDFISH)	+= rtc-goldfish.o

drivers/rtc/rtc-fsl-ftm-alarm.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Freescale FlexTimer Module (FTM) alarm device driver.
+ *
+ * Copyright 2014 Freescale Semiconductor, Inc.
+ * Copyright 2019 NXP
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/module.h>
+#include <linux/fsl/ftm.h>
+#include <linux/rtc.h>
+#include <linux/time.h>
+
+#define FTM_SC_CLK(c)		((c) << FTM_SC_CLK_MASK_SHIFT)
+
+/*
+ * Select Fixed frequency clock (32KHz) as clock source
+ * of FlexTimer Module
+ */
+#define FTM_SC_CLKS_FIXED_FREQ	0x02
+#define FIXED_FREQ_CLK		32000
+
+/* Select 128 (2^7) as divider factor */
+#define MAX_FREQ_DIV		(1 << FTM_SC_PS_MASK)
+
+/* Maximum counter value in FlexTimer's CNT registers */
+#define MAX_COUNT_VAL		0xffff
+
+struct ftm_rtc {
+	struct rtc_device *rtc_dev;
+	void __iomem *base;
+	bool big_endian;
+	u32 alarm_freq;
+};
+
+static inline u32 rtc_readl(struct ftm_rtc *dev, u32 reg)
+{
+	if (dev->big_endian)
+		return ioread32be(dev->base + reg);
+	else
+		return ioread32(dev->base + reg);
+}
+
+static inline void rtc_writel(struct ftm_rtc *dev, u32 reg, u32 val)
+{
+	if (dev->big_endian)
+		iowrite32be(val, dev->base + reg);
+	else
+		iowrite32(val, dev->base + reg);
+}
+
+static inline void ftm_counter_enable(struct ftm_rtc *rtc)
+{
+	u32 val;
+
+	/* select and enable counter clock source */
+	val = rtc_readl(rtc, FTM_SC);
+	val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
+	val |= (FTM_SC_PS_MASK | FTM_SC_CLK(FTM_SC_CLKS_FIXED_FREQ));
+	rtc_writel(rtc, FTM_SC, val);
+}
+
+static inline void ftm_counter_disable(struct ftm_rtc *rtc)
+{
+	u32 val;
+
+	/* disable counter clock source */
+	val = rtc_readl(rtc, FTM_SC);
+	val &= ~(FTM_SC_PS_MASK | FTM_SC_CLK_MASK);
+	rtc_writel(rtc, FTM_SC, val);
+}
+
+static inline void ftm_irq_acknowledge(struct ftm_rtc *rtc)
+{
+	unsigned int timeout = 100;
+
+	/*
+	 *Fix errata A-007728 for flextimer
+	 *	If the FTM counter reaches the FTM_MOD value between
+	 *	the reading of the TOF bit and the writing of 0 to
+	 *	the TOF bit, the process of clearing the TOF bit
+	 *	does not work as expected when FTMx_CONF[NUMTOF] != 0
+	 *	and the current TOF count is less than FTMx_CONF[NUMTOF].
+	 *	If the above condition is met, the TOF bit remains set.
+	 *	If the TOF interrupt is enabled (FTMx_SC[TOIE] = 1),the
+	 *	TOF interrupt also remains asserted.
+	 *
+	 *	Above is the errata discription
+	 *
+	 *	In one word: software clearing TOF bit not works when
+	 *	FTMx_CONF[NUMTOF] was seted as nonzero and FTM counter
+	 *	reaches the FTM_MOD value.
+	 *
+	 *	The workaround is clearing TOF bit until it works
+	 *	(FTM counter doesn't always reache the FTM_MOD anyway),
+	 *	which may cost some cycles.
+	 */
+	while ((FTM_SC_TOF & rtc_readl(rtc, FTM_SC)) && timeout--)
+		rtc_writel(rtc, FTM_SC, rtc_readl(rtc, FTM_SC) & (~FTM_SC_TOF));
+}
+
+static inline void ftm_irq_enable(struct ftm_rtc *rtc)
+{
+	u32 val;
+
+	val = rtc_readl(rtc, FTM_SC);
+	val |= FTM_SC_TOIE;
+	rtc_writel(rtc, FTM_SC, val);
+}
+
+static inline void ftm_irq_disable(struct ftm_rtc *rtc)
+{
+	u32 val;
+
+	val = rtc_readl(rtc, FTM_SC);
+	val &= ~FTM_SC_TOIE;
+	rtc_writel(rtc, FTM_SC, val);
+}
+
+static inline void ftm_reset_counter(struct ftm_rtc *rtc)
+{
+	/*
+	 * The CNT register contains the FTM counter value.
+	 * Reset clears the CNT register. Writing any value to COUNT
+	 * updates the counter with its initial value, CNTIN.
+	 */
+	rtc_writel(rtc, FTM_CNT, 0x00);
+}
+
+static void ftm_clean_alarm(struct ftm_rtc *rtc)
+{
+	ftm_counter_disable(rtc);
+
+	rtc_writel(rtc, FTM_CNTIN, 0x00);
+	rtc_writel(rtc, FTM_MOD, ~0U);
+
+	ftm_reset_counter(rtc);
+}
+
+static irqreturn_t ftm_rtc_alarm_interrupt(int irq, void *dev)
+{
+	struct ftm_rtc *rtc = dev;
+
+	ftm_irq_acknowledge(rtc);
+	ftm_irq_disable(rtc);
+	ftm_clean_alarm(rtc);
+
+	return IRQ_HANDLED;
+}
+
+static int ftm_rtc_alarm_irq_enable(struct device *dev,
+		unsigned int enabled)
+{
+	struct ftm_rtc *rtc = dev_get_drvdata(dev);
+
+	if (enabled)
+		ftm_irq_enable(rtc);
+	else
+		ftm_irq_disable(rtc);
+
+	return 0;
+}
+
+/*
+ * Note:
+ *	The function is not really getting time from the RTC
+ *	since FlexTimer is not a RTC device, but we need to
+ *	get time to setup alarm, so we are using system time
+ *	for now.
+ */
+static int ftm_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct timespec64 ts64;
+
+	ktime_get_real_ts64(&ts64);
+	rtc_time_to_tm(ts64.tv_sec, tm);
+
+	return 0;
+}
+
+static int ftm_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	return 0;
+}
+
+/*
+ * 1. Select fixed frequency clock (32KHz) as clock source;
+ * 2. Select 128 (2^7) as divider factor;
+ * So clock is 250 Hz (32KHz/128).
+ *
+ * 3. FlexTimer's CNT register is a 32bit register,
+ * but the register's 16 bit as counter value,it's other 16 bit
+ * is reserved.So minimum counter value is 0x0,maximum counter
+ * value is 0xffff.
+ * So max alarm value is 262 (65536 / 250) seconds
+ */
+static int ftm_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alm)
+{
+	struct rtc_time tm;
+	unsigned long now, alm_time, cycle;
+	struct ftm_rtc *rtc = dev_get_drvdata(dev);
+
+	ftm_rtc_read_time(dev, &tm);
+	rtc_tm_to_time(&tm, &now);
+	rtc_tm_to_time(&alm->time, &alm_time);
+
+	ftm_clean_alarm(rtc);
+	cycle = (alm_time - now) * rtc->alarm_freq;
+	if (cycle > MAX_COUNT_VAL) {
+		pr_err("Out of alarm range {0~262} seconds.\n");
+		return -ERANGE;
+	}
+
+	ftm_irq_disable(rtc);
+
+	/*
+	 * The counter increments until the value of MOD is reached,
+	 * at which point the counter is reloaded with the value of CNTIN.
+	 * The TOF (the overflow flag) bit is set when the FTM counter
+	 * changes from MOD to CNTIN. So we should using the cycle - 1.
+	 */
+	rtc_writel(rtc, FTM_MOD, cycle - 1);
+
+	ftm_counter_enable(rtc);
+	ftm_irq_enable(rtc);
+
+	return 0;
+
+}
+
+static const struct rtc_class_ops ftm_rtc_ops = {
+	.read_time		= ftm_rtc_read_time,
+	.read_alarm		= ftm_rtc_read_alarm,
+	.set_alarm		= ftm_rtc_set_alarm,
+	.alarm_irq_enable	= ftm_rtc_alarm_irq_enable,
+};
+
+static int ftm_rtc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct resource *r;
+	int irq;
+	int ret;
+	struct ftm_rtc *rtc;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (unlikely(!rtc)) {
+		dev_err(&pdev->dev, "cannot alloc memory for rtc\n");
+		return -ENOMEM;
+	}
+
+	platform_set_drvdata(pdev, rtc);
+
+	rtc->rtc_dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtc_dev))
+		return PTR_ERR(rtc->rtc_dev);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "cannot get resource for rtc\n");
+		return -ENODEV;
+	}
+
+	rtc->base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(rtc->base)) {
+		dev_err(&pdev->dev, "cannot ioremap resource for rtc\n");
+		return PTR_ERR(rtc->base);
+	}
+
+	irq = irq_of_parse_and_map(np, 0);
+	if (irq <= 0) {
+		dev_err(&pdev->dev, "unable to get IRQ from DT, %d\n", irq);
+		return -EINVAL;
+	}
+
+	ret = devm_request_irq(&pdev->dev, irq, ftm_rtc_alarm_interrupt,
+			       IRQF_NO_SUSPEND, dev_name(&pdev->dev), rtc);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to request irq\n");
+		return ret;
+	}
+
+	rtc->big_endian = of_property_read_bool(np, "big-endian");
+	rtc->alarm_freq = (u32)FIXED_FREQ_CLK / (u32)MAX_FREQ_DIV;
+	rtc->rtc_dev->ops = &ftm_rtc_ops;
+
+	device_init_wakeup(&pdev->dev, true);
+
+	ret = rtc_register_device(rtc->rtc_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "can't register rtc device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id ftm_rtc_match[] = {
+	{ .compatible = "fsl,ls1012a-ftm-alarm", },
+	{ .compatible = "fsl,ls1021a-ftm-alarm", },
+	{ .compatible = "fsl,ls1028a-ftm-alarm", },
+	{ .compatible = "fsl,ls1043a-ftm-alarm", },
+	{ .compatible = "fsl,ls1046a-ftm-alarm", },
+	{ .compatible = "fsl,ls1088a-ftm-alarm", },
+	{ .compatible = "fsl,ls208xa-ftm-alarm", },
+	{ .compatible = "fsl,lx2160a-ftm-alarm", },
+	{ },
+};
+
+static struct platform_driver ftm_rtc_driver = {
+	.probe		= ftm_rtc_probe,
+	.driver		= {
+		.name	= "ftm-alarm",
+		.of_match_table = ftm_rtc_match,
+	},
+};
+
+static int __init ftm_alarm_init(void)
+{
+	return platform_driver_register(&ftm_rtc_driver);
+}
+
+device_initcall(ftm_alarm_init);
+
+MODULE_DESCRIPTION("NXP/Freescale FlexTimer alarm driver");
+MODULE_AUTHOR("Biwen Li <[e-mail]>");
+MODULE_LICENSE("GPL");