MIPS: ralink: Add support for periodic timer irq

Adds a driver for the periodic timer found on Ralink SoC.

Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5682/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 186 insertions, 1 deletions

diff --git a/arch/mips/ralink/Makefile b/arch/mips/ralink/Makefile
index 38cf1a880aaa..e37e0ec5b378 100644
--- a/arch/mips/ralink/Makefile
+++ b/arch/mips/ralink/Makefile
@@ -6,7 +6,7 @@
 # Copyright (C) 2009-2011 Gabor Juhos <juhosg@openwrt.org>
 # Copyright (C) 2013 John Crispin <blogic@openwrt.org>
 
-obj-y := prom.o of.o reset.o clk.o irq.o
+obj-y := prom.o of.o reset.o clk.o irq.o timer.o
 
 obj-$(CONFIG_SOC_RT288X) += rt288x.o
 obj-$(CONFIG_SOC_RT305X) += rt305x.o
diff --git a/arch/mips/ralink/timer.c b/arch/mips/ralink/timer.c
new file mode 100644
index 000000000000..e49241a2c39a
--- /dev/null
+++ b/arch/mips/ralink/timer.c
@@ -0,0 +1,185 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * Copyright (C) 2013 John Crispin <blogic@openwrt.org>
+*/
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/timer.h>
+#include <linux/of_gpio.h>
+#include <linux/clk.h>
+
+#include <asm/mach-ralink/ralink_regs.h>
+
+#define TIMER_REG_TMRSTAT               0x00
+#define TIMER_REG_TMR0LOAD              0x10
+#define TIMER_REG_TMR0CTL               0x18
+
+#define TMRSTAT_TMR0INT                 BIT(0)
+
+#define TMR0CTL_ENABLE                  BIT(7)
+#define TMR0CTL_MODE_PERIODIC           BIT(4)
+#define TMR0CTL_PRESCALER               1
+#define TMR0CTL_PRESCALE_VAL            (0xf - TMR0CTL_PRESCALER)
+#define TMR0CTL_PRESCALE_DIV            (65536 / BIT(TMR0CTL_PRESCALER))
+
+struct rt_timer {
+        struct device   *dev;
+        void __iomem    *membase;
+        int             irq;
+        unsigned long   timer_freq;
+        unsigned long   timer_div;
+};
+
+static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
+{
+        __raw_writel(val, rt->membase + reg);
+}
+
+static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
+{
+        return __raw_readl(rt->membase + reg);
+}
+
+static irqreturn_t rt_timer_irq(int irq, void *_rt)
+{
+        struct rt_timer *rt =  (struct rt_timer *) _rt;
+
+        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
+        rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);
+
+        return IRQ_HANDLED;
+}
+
+
+static int rt_timer_request(struct rt_timer *rt)
+{
+        int err = request_irq(rt->irq, rt_timer_irq, IRQF_DISABLED,
+                                                dev_name(rt->dev), rt);
+        if (err) {
+                dev_err(rt->dev, "failed to request irq\n");
+        } else {
+                u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
+                rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
+        }
+        return err;
+}
+
+static void rt_timer_free(struct rt_timer *rt)
+{
+        free_irq(rt->irq, rt);
+}
+
+static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
+{
+        if (rt->timer_freq < divisor)
+                rt->timer_div = rt->timer_freq;
+        else
+                rt->timer_div = divisor;
+
+        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
+
+        return 0;
+}
+
+static int rt_timer_enable(struct rt_timer *rt)
+{
+        u32 t;
+
+        rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
+
+        t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
+        t |= TMR0CTL_ENABLE;
+        rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
+
+        return 0;
+}
+
+static void rt_timer_disable(struct rt_timer *rt)
+{
+        u32 t;
+
+        t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
+        t &= ~TMR0CTL_ENABLE;
+        rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
+}
+
+static int rt_timer_probe(struct platform_device *pdev)
+{
+        struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        struct rt_timer *rt;
+        struct clk *clk;
+
+        rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
+        if (!rt) {
+                dev_err(&pdev->dev, "failed to allocate memory\n");
+                return -ENOMEM;
+        }
+
+        rt->irq = platform_get_irq(pdev, 0);
+        if (!rt->irq) {
+                dev_err(&pdev->dev, "failed to load irq\n");
+                return -ENOENT;
+        }
+
+        rt->membase = devm_request_and_ioremap(&pdev->dev, res);
+        if (IS_ERR(rt->membase))
+                return PTR_ERR(rt->membase);
+
+        clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(clk)) {
+                dev_err(&pdev->dev, "failed get clock rate\n");
+                return PTR_ERR(clk);
+        }
+
+        rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
+        if (!rt->timer_freq)
+                return -EINVAL;
+
+        rt->dev = &pdev->dev;
+        platform_set_drvdata(pdev, rt);
+
+        rt_timer_request(rt);
+        rt_timer_config(rt, 2);
+        rt_timer_enable(rt);
+
+        dev_info(&pdev->dev, "maximum frequncy is %luHz\n", rt->timer_freq);
+
+        return 0;
+}
+
+static int rt_timer_remove(struct platform_device *pdev)
+{
+        struct rt_timer *rt = platform_get_drvdata(pdev);
+
+        rt_timer_disable(rt);
+        rt_timer_free(rt);
+
+        return 0;
+}
+
+static const struct of_device_id rt_timer_match[] = {
+        { .compatible = "ralink,rt2880-timer" },
+        {},
+};
+MODULE_DEVICE_TABLE(of, rt_timer_match);
+
+static struct platform_driver rt_timer_driver = {
+        .probe = rt_timer_probe,
+        .remove = rt_timer_remove,
+        .driver = {
+                .name           = "rt-timer",
+                .owner          = THIS_MODULE,
+                .of_match_table = rt_timer_match
+        },
+};
+
+module_platform_driver(rt_timer_driver);
+
+MODULE_DESCRIPTION("Ralink RT2880 timer");
+MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
+MODULE_LICENSE("GPL");