rtc: pic32: Add PIC32 real time clock driver

This driver adds support for the PIC32 real time clock and calendar
peripheral:
- reading and setting time
- alarms provided by dedicated IRQ

Signed-off-by: Joshua Henderson <[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-xgene".
 
+config RTC_DRV_PIC32
+	tristate "Microchip PIC32 RTC"
+	depends on MACH_PIC32
+	default y
+	help
+	   If you say yes here you get support for the PIC32 RTC module.
+
+	   This driver can also be built as a module. If so, the module
+	   will be called rtc-pic32
+
 comment "HID Sensor RTC drivers"
 
 config RTC_DRV_HID_SENSOR_TIME

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_PCF8523)	+= rtc-pcf8523.o
 obj-$(CONFIG_RTC_DRV_PCF8563)	+= rtc-pcf8563.o
 obj-$(CONFIG_RTC_DRV_PCF8583)	+= rtc-pcf8583.o
+obj-$(CONFIG_RTC_DRV_PIC32)	+= rtc-pic32.o
 obj-$(CONFIG_RTC_DRV_PL030)	+= rtc-pl030.o
 obj-$(CONFIG_RTC_DRV_PL031)	+= rtc-pl031.o
 obj-$(CONFIG_RTC_DRV_PM8XXX)	+= rtc-pm8xxx.o

drivers/rtc/rtc-pic32.c

···
+/*
+ * PIC32 RTC driver
+ *
+ * Joshua Henderson <[e-mail]>
+ * Copyright (C) 2016 Microchip Technology Inc.  All rights reserved.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that 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/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/clk.h>
+#include <linux/rtc.h>
+#include <linux/bcd.h>
+
+#include <asm/mach-pic32/pic32.h>
+
+#define PIC32_RTCCON		0x00
+#define PIC32_RTCCON_ON		BIT(15)
+#define PIC32_RTCCON_SIDL	BIT(13)
+#define PIC32_RTCCON_RTCCLKSEL	(3 << 9)
+#define PIC32_RTCCON_RTCCLKON	BIT(6)
+#define PIC32_RTCCON_RTCWREN	BIT(3)
+#define PIC32_RTCCON_RTCSYNC	BIT(2)
+#define PIC32_RTCCON_HALFSEC	BIT(1)
+#define PIC32_RTCCON_RTCOE	BIT(0)
+
+#define PIC32_RTCALRM		0x10
+#define PIC32_RTCALRM_ALRMEN	BIT(15)
+#define PIC32_RTCALRM_CHIME	BIT(14)
+#define PIC32_RTCALRM_PIV	BIT(13)
+#define PIC32_RTCALRM_ALARMSYNC	BIT(12)
+#define PIC32_RTCALRM_AMASK	0x0F00
+#define PIC32_RTCALRM_ARPT	0xFF
+
+#define PIC32_RTCHOUR		0x23
+#define PIC32_RTCMIN		0x22
+#define PIC32_RTCSEC		0x21
+#define PIC32_RTCYEAR		0x33
+#define PIC32_RTCMON		0x32
+#define PIC32_RTCDAY		0x31
+
+#define PIC32_ALRMTIME		0x40
+#define PIC32_ALRMDATE		0x50
+
+#define PIC32_ALRMHOUR		0x43
+#define PIC32_ALRMMIN		0x42
+#define PIC32_ALRMSEC		0x41
+#define PIC32_ALRMYEAR		0x53
+#define PIC32_ALRMMON		0x52
+#define PIC32_ALRMDAY		0x51
+
+struct pic32_rtc_dev {
+	struct rtc_device	*rtc;
+	void __iomem		*reg_base;
+	struct clk		*clk;
+	spinlock_t		alarm_lock;
+	int			alarm_irq;
+	bool			alarm_clk_enabled;
+};
+
+static void pic32_rtc_alarm_clk_enable(struct pic32_rtc_dev *pdata,
+				       bool enable)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pdata->alarm_lock, flags);
+	if (enable) {
+		if (!pdata->alarm_clk_enabled) {
+			clk_enable(pdata->clk);
+			pdata->alarm_clk_enabled = true;
+		}
+	} else {
+		if (pdata->alarm_clk_enabled) {
+			clk_disable(pdata->clk);
+			pdata->alarm_clk_enabled = false;
+		}
+	}
+	spin_unlock_irqrestore(&pdata->alarm_lock, flags);
+}
+
+static irqreturn_t pic32_rtc_alarmirq(int irq, void *id)
+{
+	struct pic32_rtc_dev *pdata = (struct pic32_rtc_dev *)id;
+
+	clk_enable(pdata->clk);
+	rtc_update_irq(pdata->rtc, 1, RTC_AF | RTC_IRQF);
+	clk_disable(pdata->clk);
+
+	pic32_rtc_alarm_clk_enable(pdata, false);
+
+	return IRQ_HANDLED;
+}
+
+static int pic32_rtc_setaie(struct device *dev, unsigned int enabled)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	void __iomem *base = pdata->reg_base;
+
+	clk_enable(pdata->clk);
+
+	writel(PIC32_RTCALRM_ALRMEN,
+	       base + (enabled ? PIC32_SET(PIC32_RTCALRM) :
+		       PIC32_CLR(PIC32_RTCALRM)));
+
+	clk_disable(pdata->clk);
+
+	pic32_rtc_alarm_clk_enable(pdata, enabled);
+
+	return 0;
+}
+
+static int pic32_rtc_setfreq(struct device *dev, int freq)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	void __iomem *base = pdata->reg_base;
+
+	clk_enable(pdata->clk);
+
+	writel(PIC32_RTCALRM_AMASK, base + PIC32_CLR(PIC32_RTCALRM));
+	writel(freq << 8, base + PIC32_SET(PIC32_RTCALRM));
+	writel(PIC32_RTCALRM_CHIME, base + PIC32_SET(PIC32_RTCALRM));
+
+	clk_disable(pdata->clk);
+
+	return 0;
+}
+
+static int pic32_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	void __iomem *base = pdata->reg_base;
+	unsigned int tries = 0;
+
+	clk_enable(pdata->clk);
+
+	do {
+		rtc_tm->tm_hour = readb(base + PIC32_RTCHOUR);
+		rtc_tm->tm_min = readb(base + PIC32_RTCMIN);
+		rtc_tm->tm_mon  = readb(base + PIC32_RTCMON);
+		rtc_tm->tm_mday = readb(base + PIC32_RTCDAY);
+		rtc_tm->tm_year = readb(base + PIC32_RTCYEAR);
+		rtc_tm->tm_sec  = readb(base + PIC32_RTCSEC);
+
+		/*
+		 * The only way to work out whether the system was mid-update
+		 * when we read it is to check the second counter, and if it
+		 * is zero, then we re-try the entire read.
+		 */
+		tries += 1;
+	} while (rtc_tm->tm_sec == 0 && tries < 2);
+
+	rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
+	rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
+	rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
+	rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
+	rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon) - 1;
+	rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
+
+	rtc_tm->tm_year += 100;
+
+	dev_dbg(dev, "read time %04d.%02d.%02d %02d:%02d:%02d\n",
+		1900 + rtc_tm->tm_year, rtc_tm->tm_mon, rtc_tm->tm_mday,
+		rtc_tm->tm_hour, rtc_tm->tm_min, rtc_tm->tm_sec);
+
+	clk_disable(pdata->clk);
+	return rtc_valid_tm(rtc_tm);
+}
+
+static int pic32_rtc_settime(struct device *dev, struct rtc_time *tm)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	void __iomem *base = pdata->reg_base;
+	int year = tm->tm_year - 100;
+
+	dev_dbg(dev, "set time %04d.%02d.%02d %02d:%02d:%02d\n",
+		1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
+		tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+	if (year < 0 || year >= 100) {
+		dev_err(dev, "rtc only supports 100 years\n");
+		return -EINVAL;
+	}
+
+	clk_enable(pdata->clk);
+	writeb(bin2bcd(tm->tm_sec),  base + PIC32_RTCSEC);
+	writeb(bin2bcd(tm->tm_min),  base + PIC32_RTCMIN);
+	writeb(bin2bcd(tm->tm_hour), base + PIC32_RTCHOUR);
+	writeb(bin2bcd(tm->tm_mday), base + PIC32_RTCDAY);
+	writeb(bin2bcd(tm->tm_mon + 1), base + PIC32_RTCMON);
+	writeb(bin2bcd(year), base + PIC32_RTCYEAR);
+	clk_disable(pdata->clk);
+
+	return 0;
+}
+
+static int pic32_rtc_getalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	struct rtc_time *alm_tm = &alrm->time;
+	void __iomem *base = pdata->reg_base;
+	unsigned int alm_en;
+
+	clk_enable(pdata->clk);
+	alm_tm->tm_sec  = readb(base + PIC32_ALRMSEC);
+	alm_tm->tm_min  = readb(base + PIC32_ALRMMIN);
+	alm_tm->tm_hour = readb(base + PIC32_ALRMHOUR);
+	alm_tm->tm_mon  = readb(base + PIC32_ALRMMON);
+	alm_tm->tm_mday = readb(base + PIC32_ALRMDAY);
+	alm_tm->tm_year = readb(base + PIC32_ALRMYEAR);
+
+	alm_en = readb(base + PIC32_RTCALRM);
+
+	alrm->enabled = (alm_en & PIC32_RTCALRM_ALRMEN) ? 1 : 0;
+
+	dev_dbg(dev, "getalarm: %d, %04d.%02d.%02d %02d:%02d:%02d\n",
+		alm_en,
+		1900 + alm_tm->tm_year, alm_tm->tm_mon, alm_tm->tm_mday,
+		alm_tm->tm_hour, alm_tm->tm_min, alm_tm->tm_sec);
+
+	alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
+	alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
+	alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
+	alm_tm->tm_mday = bcd2bin(alm_tm->tm_mday);
+	alm_tm->tm_mon = bcd2bin(alm_tm->tm_mon) - 1;
+	alm_tm->tm_year = bcd2bin(alm_tm->tm_year);
+
+	clk_disable(pdata->clk);
+	return 0;
+}
+
+static int pic32_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	struct rtc_time *tm = &alrm->time;
+	void __iomem *base = pdata->reg_base;
+
+	clk_enable(pdata->clk);
+	dev_dbg(dev, "setalarm: %d, %04d.%02d.%02d %02d:%02d:%02d\n",
+		alrm->enabled,
+		1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday,
+		tm->tm_hour, tm->tm_min, tm->tm_sec);
+
+	writel(0x00, base + PIC32_ALRMTIME);
+	writel(0x00, base + PIC32_ALRMDATE);
+
+	pic32_rtc_setaie(dev, alrm->enabled);
+
+	clk_disable(pdata->clk);
+	return 0;
+}
+
+static int pic32_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+	struct pic32_rtc_dev *pdata = dev_get_drvdata(dev);
+	void __iomem *base = pdata->reg_base;
+	unsigned int repeat;
+
+	clk_enable(pdata->clk);
+
+	repeat = readw(base + PIC32_RTCALRM);
+	repeat &= PIC32_RTCALRM_ARPT;
+	seq_printf(seq, "periodic_IRQ\t: %s\n", repeat  ? "yes" : "no");
+
+	clk_disable(pdata->clk);
+	return 0;
+}
+
+static const struct rtc_class_ops pic32_rtcops = {
+	.read_time	  = pic32_rtc_gettime,
+	.set_time	  = pic32_rtc_settime,
+	.read_alarm	  = pic32_rtc_getalarm,
+	.set_alarm	  = pic32_rtc_setalarm,
+	.proc		  = pic32_rtc_proc,
+	.alarm_irq_enable = pic32_rtc_setaie,
+};
+
+static void pic32_rtc_enable(struct pic32_rtc_dev *pdata, int en)
+{
+	void __iomem *base = pdata->reg_base;
+
+	if (!base)
+		return;
+
+	clk_enable(pdata->clk);
+	if (!en) {
+		writel(PIC32_RTCCON_ON, base + PIC32_CLR(PIC32_RTCCON));
+	} else {
+		pic32_syskey_unlock();
+
+		writel(PIC32_RTCCON_RTCWREN, base + PIC32_SET(PIC32_RTCCON));
+		writel(3 << 9, base + PIC32_CLR(PIC32_RTCCON));
+
+		if (!(readl(base + PIC32_RTCCON) & PIC32_RTCCON_ON))
+			writel(PIC32_RTCCON_ON, base + PIC32_SET(PIC32_RTCCON));
+	}
+	clk_disable(pdata->clk);
+}
+
+static int pic32_rtc_remove(struct platform_device *pdev)
+{
+	struct pic32_rtc_dev *pdata = platform_get_drvdata(pdev);
+
+	pic32_rtc_setaie(&pdev->dev, 0);
+	clk_unprepare(pdata->clk);
+	pdata->clk = NULL;
+
+	return 0;
+}
+
+static int pic32_rtc_probe(struct platform_device *pdev)
+{
+	struct pic32_rtc_dev *pdata;
+	struct resource *res;
+	int ret;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, pdata);
+
+	pdata->alarm_irq = platform_get_irq(pdev, 0);
+	if (pdata->alarm_irq < 0) {
+		dev_err(&pdev->dev, "no irq for alarm\n");
+		return pdata->alarm_irq;
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pdata->reg_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(pdata->reg_base))
+		return PTR_ERR(pdata->reg_base);
+
+	pdata->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pdata->clk)) {
+		dev_err(&pdev->dev, "failed to find rtc clock source\n");
+		ret = PTR_ERR(pdata->clk);
+		pdata->clk = NULL;
+		return ret;
+	}
+
+	spin_lock_init(&pdata->alarm_lock);
+
+	clk_prepare_enable(pdata->clk);
+
+	pic32_rtc_enable(pdata, 1);
+
+	device_init_wakeup(&pdev->dev, 1);
+
+	pdata->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
+						 &pic32_rtcops,
+						 THIS_MODULE);
+	if (IS_ERR(pdata->rtc)) {
+		ret = PTR_ERR(pdata->rtc);
+		goto err_nortc;
+	}
+
+	pdata->rtc->max_user_freq = 128;
+
+	pic32_rtc_setfreq(&pdev->dev, 1);
+	ret = devm_request_irq(&pdev->dev, pdata->alarm_irq,
+			       pic32_rtc_alarmirq, 0,
+			       dev_name(&pdev->dev), pdata);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"IRQ %d error %d\n", pdata->alarm_irq, ret);
+		goto err_nortc;
+	}
+
+	clk_disable(pdata->clk);
+
+	return 0;
+
+err_nortc:
+	pic32_rtc_enable(pdata, 0);
+	clk_disable_unprepare(pdata->clk);
+
+	return ret;
+}
+
+static const struct of_device_id pic32_rtc_dt_ids[] = {
+	{ .compatible = "microchip,pic32mzda-rtc" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pic32_rtc_dt_ids);
+
+static struct platform_driver pic32_rtc_driver = {
+	.probe		= pic32_rtc_probe,
+	.remove		= pic32_rtc_remove,
+	.driver		= {
+		.name	= "pic32-rtc",
+		.owner	= THIS_MODULE,
+		.of_match_table	= of_match_ptr(pic32_rtc_dt_ids),
+	},
+};
+module_platform_driver(pic32_rtc_driver);
+
+MODULE_DESCRIPTION("Microchip PIC32 RTC Driver");
+MODULE_AUTHOR("Joshua Henderson <[e-mail]>");
+MODULE_LICENSE("GPL");