rtc: driver for Conexant Digicolor CX92755 on-chip RTC

Add driver for the RTC hardware block on the Conexant CX92755 SoC, from
the Digicolor series of SoCs.  Tested on the Equinox evaluation board for
the CX92755 chip.

[akpm@linux-foundation.org: build command arrays at compile-time]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 238 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index b5b5c3d485d6..faeee2d2550b 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1111,6 +1111,16 @@ config RTC_DRV_DAVINCI
           This driver can also be built as a module. If so, the module
           will be called rtc-davinci.
 
+config RTC_DRV_DIGICOLOR
+        tristate "Conexant Digicolor RTC"
+        depends on ARCH_DIGICOLOR
+        help
+          If you say yes here you get support for the RTC on Conexant
+          Digicolor platforms. This currently includes the CX92755 SoC.
+
+          This driver can also be built as a module. If so, the module
+          will be called rtc-digicolor.
+
 config RTC_DRV_IMXDI
         tristate "Freescale IMX DryIce Real Time Clock"
         depends on ARCH_MXC
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 69c87062b098..c31731c29762 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_RTC_DRV_DA9052)	+= rtc-da9052.o
 obj-$(CONFIG_RTC_DRV_DA9055)    += rtc-da9055.o
 obj-$(CONFIG_RTC_DRV_DA9063)    += rtc-da9063.o
 obj-$(CONFIG_RTC_DRV_DAVINCI)   += rtc-davinci.o
+obj-$(CONFIG_RTC_DRV_DIGICOLOR) += rtc-digicolor.o
 obj-$(CONFIG_RTC_DRV_DM355EVM)  += rtc-dm355evm.o
 obj-$(CONFIG_RTC_DRV_VRTC)      += rtc-mrst.o
 obj-$(CONFIG_RTC_DRV_DS1216)    += rtc-ds1216.o
diff --git a/drivers/rtc/rtc-digicolor.c b/drivers/rtc/rtc-digicolor.c
new file mode 100644
index 000000000000..8d05596a6765
--- /dev/null
+++ b/drivers/rtc/rtc-digicolor.c
@@ -0,0 +1,227 @@
+/*
+ * Real Time Clock driver for Conexant Digicolor
+ *
+ * Copyright (C) 2015 Paradox Innovation Ltd.
+ *
+ * Author: Baruch Siach <baruch@tkos.co.il>
+ *
+ * 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/io.h>
+#include <linux/iopoll.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/of.h>
+
+#define DC_RTC_CONTROL          0x0
+#define DC_RTC_TIME             0x8
+#define DC_RTC_REFERENCE        0xc
+#define DC_RTC_ALARM            0x10
+#define DC_RTC_INTFLAG_CLEAR    0x14
+#define DC_RTC_INTENABLE        0x16
+
+#define DC_RTC_CMD_MASK         0xf
+#define DC_RTC_GO_BUSY          BIT(7)
+
+#define CMD_NOP                 0
+#define CMD_RESET               1
+#define CMD_WRITE               3
+#define CMD_READ                4
+
+#define CMD_DELAY_US            (10*1000)
+#define CMD_TIMEOUT_US          (500*CMD_DELAY_US)
+
+struct dc_rtc {
+        struct rtc_device       *rtc_dev;
+        void __iomem            *regs;
+};
+
+static int dc_rtc_cmds(struct dc_rtc *rtc, const u8 *cmds, int len)
+{
+        u8 val;
+        int i, ret;
+
+        for (i = 0; i < len; i++) {
+                writeb_relaxed((cmds[i] & DC_RTC_CMD_MASK) | DC_RTC_GO_BUSY,
+                               rtc->regs + DC_RTC_CONTROL);
+                ret = readb_relaxed_poll_timeout(
+                        rtc->regs + DC_RTC_CONTROL, val,
+                        !(val & DC_RTC_GO_BUSY), CMD_DELAY_US, CMD_TIMEOUT_US);
+                if (ret < 0)
+                        return ret;
+        }
+
+        return 0;
+}
+
+static int dc_rtc_read(struct dc_rtc *rtc, unsigned long *val)
+{
+        static const u8 read_cmds[] = {CMD_READ, CMD_NOP};
+        u32 reference, time1, time2;
+        int ret;
+
+        ret = dc_rtc_cmds(rtc, read_cmds, ARRAY_SIZE(read_cmds));
+        if (ret < 0)
+                return ret;
+
+        reference = readl_relaxed(rtc->regs + DC_RTC_REFERENCE);
+        time1 = readl_relaxed(rtc->regs + DC_RTC_TIME);
+        /* Read twice to ensure consistency */
+        while (1) {
+                time2 = readl_relaxed(rtc->regs + DC_RTC_TIME);
+                if (time1 == time2)
+                        break;
+                time1 = time2;
+        }
+
+        *val = reference + time1;
+        return 0;
+}
+
+static int dc_rtc_write(struct dc_rtc *rtc, u32 val)
+{
+        static const u8 write_cmds[] = {CMD_WRITE, CMD_NOP, CMD_RESET, CMD_NOP};
+
+        writel_relaxed(val, rtc->regs + DC_RTC_REFERENCE);
+        return dc_rtc_cmds(rtc, write_cmds, ARRAY_SIZE(write_cmds));
+}
+
+static int dc_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+        struct dc_rtc *rtc = dev_get_drvdata(dev);
+        unsigned long now;
+        int ret;
+
+        ret = dc_rtc_read(rtc, &now);
+        if (ret < 0)
+                return ret;
+        rtc_time64_to_tm(now, tm);
+
+        return 0;
+}
+
+static int dc_rtc_set_mmss(struct device *dev, unsigned long secs)
+{
+        struct dc_rtc *rtc = dev_get_drvdata(dev);
+
+        return dc_rtc_write(rtc, secs);
+}
+
+static int dc_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+        struct dc_rtc *rtc = dev_get_drvdata(dev);
+        u32 alarm_reg, reference;
+        unsigned long now;
+        int ret;
+
+        alarm_reg = readl_relaxed(rtc->regs + DC_RTC_ALARM);
+        reference = readl_relaxed(rtc->regs + DC_RTC_REFERENCE);
+        rtc_time64_to_tm(reference + alarm_reg, &alarm->time);
+
+        ret = dc_rtc_read(rtc, &now);
+        if (ret < 0)
+                return ret;
+
+        alarm->pending = alarm_reg + reference > now;
+        alarm->enabled = readl_relaxed(rtc->regs + DC_RTC_INTENABLE);
+
+        return 0;
+}
+
+static int dc_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+        struct dc_rtc *rtc = dev_get_drvdata(dev);
+        time64_t alarm_time;
+        u32 reference;
+
+        alarm_time = rtc_tm_to_time64(&alarm->time);
+
+        reference = readl_relaxed(rtc->regs + DC_RTC_REFERENCE);
+        writel_relaxed(alarm_time - reference, rtc->regs + DC_RTC_ALARM);
+
+        writeb_relaxed(!!alarm->enabled, rtc->regs + DC_RTC_INTENABLE);
+
+        return 0;
+}
+
+static int dc_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+        struct dc_rtc *rtc = dev_get_drvdata(dev);
+
+        writeb_relaxed(!!enabled, rtc->regs + DC_RTC_INTENABLE);
+
+        return 0;
+}
+
+static struct rtc_class_ops dc_rtc_ops = {
+        .read_time              = dc_rtc_read_time,
+        .set_mmss               = dc_rtc_set_mmss,
+        .read_alarm             = dc_rtc_read_alarm,
+        .set_alarm              = dc_rtc_set_alarm,
+        .alarm_irq_enable       = dc_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t dc_rtc_irq(int irq, void *dev_id)
+{
+        struct dc_rtc *rtc = dev_id;
+
+        writeb_relaxed(1, rtc->regs + DC_RTC_INTFLAG_CLEAR);
+        rtc_update_irq(rtc->rtc_dev, 1, RTC_AF | RTC_IRQF);
+
+        return IRQ_HANDLED;
+}
+
+static int __init dc_rtc_probe(struct platform_device *pdev)
+{
+        struct resource *res;
+        struct dc_rtc *rtc;
+        int irq, ret;
+
+        rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+        if (!rtc)
+                return -ENOMEM;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        rtc->regs = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(rtc->regs))
+                return PTR_ERR(rtc->regs);
+
+        irq = platform_get_irq(pdev, 0);
+        if (irq < 0)
+                return irq;
+        ret = devm_request_irq(&pdev->dev, irq, dc_rtc_irq, 0, pdev->name, rtc);
+        if (ret < 0)
+                return ret;
+
+        platform_set_drvdata(pdev, rtc);
+        rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, pdev->name,
+                                                &dc_rtc_ops, THIS_MODULE);
+        if (IS_ERR(rtc->rtc_dev))
+                return PTR_ERR(rtc->rtc_dev);
+
+        return 0;
+}
+
+static const struct of_device_id dc_dt_ids[] = {
+        { .compatible = "cnxt,cx92755-rtc" },
+        { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, dc_dt_ids);
+
+static struct platform_driver dc_rtc_driver = {
+        .driver = {
+                .name = "digicolor_rtc",
+                .of_match_table = of_match_ptr(dc_dt_ids),
+        },
+};
+module_platform_driver_probe(dc_rtc_driver, dc_rtc_probe);
+
+MODULE_AUTHOR("Baruch Siach <baruch@tkos.co.il>");
+MODULE_DESCRIPTION("Conexant Digicolor Realtime Clock Driver (RTC)");
+MODULE_LICENSE("GPL");