kernel/arch/mips/ralink/timer.c

   1 /*
   2  * This program is free software; you can redistribute it and/or modify it
   3  * under the terms of the GNU General Public License version 2 as published
   4  * by the Free Software Foundation.
   5  *
   6  * Copyright (C) 2013 John Crispin <blogic@openwrt.org>
   7 */
   8
   9 #include <linux/module.h>
  10 #include <linux/platform_device.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/timer.h>
  13 #include <linux/of_gpio.h>
  14 #include <linux/clk.h>
  15
  16 #include <asm/mach-ralink/ralink_regs.h>
  17
  18 #define TIMER_REG_TMRSTAT               0x00
  19 #define TIMER_REG_TMR0LOAD              0x10
  20 #define TIMER_REG_TMR0CTL               0x18
  21
  22 #define TMRSTAT_TMR0INT                 BIT(0)
  23
  24 #define TMR0CTL_ENABLE                  BIT(7)
  25 #define TMR0CTL_MODE_PERIODIC           BIT(4)
  26 #define TMR0CTL_PRESCALER               1
  27 #define TMR0CTL_PRESCALE_VAL            (0xf - TMR0CTL_PRESCALER)
  28 #define TMR0CTL_PRESCALE_DIV            (65536 / BIT(TMR0CTL_PRESCALER))
  29
  30 struct rt_timer {
  31         struct device   *dev;
  32         void __iomem    *membase;
  33         int             irq;
  34         unsigned long   timer_freq;
  35         unsigned long   timer_div;
  36 };
  37
  38 static inline void rt_timer_w32(struct rt_timer *rt, u8 reg, u32 val)
  39 {
  40         __raw_writel(val, rt->membase + reg);
  41 }
  42
  43 static inline u32 rt_timer_r32(struct rt_timer *rt, u8 reg)
  44 {
  45         return __raw_readl(rt->membase + reg);
  46 }
  47
  48 static irqreturn_t rt_timer_irq(int irq, void *_rt)
  49 {
  50         struct rt_timer *rt =  (struct rt_timer *) _rt;
  51
  52         rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
  53         rt_timer_w32(rt, TIMER_REG_TMRSTAT, TMRSTAT_TMR0INT);
  54
  55         return IRQ_HANDLED;
  56 }
  57
  58
  59 static int rt_timer_request(struct rt_timer *rt)
  60 {
  61         int err = request_irq(rt->irq, rt_timer_irq, 0,
  62                                                 dev_name(rt->dev), rt);
  63         if (err) {
  64                 dev_err(rt->dev, "failed to request irq\n");
  65         } else {
  66                 u32 t = TMR0CTL_MODE_PERIODIC | TMR0CTL_PRESCALE_VAL;
  67                 rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
  68         }
  69         return err;
  70 }
  71
  72 static void rt_timer_free(struct rt_timer *rt)
  73 {
  74         free_irq(rt->irq, rt);
  75 }
  76
  77 static int rt_timer_config(struct rt_timer *rt, unsigned long divisor)
  78 {
  79         if (rt->timer_freq < divisor)
  80                 rt->timer_div = rt->timer_freq;
  81         else
  82                 rt->timer_div = divisor;
  83
  84         rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
  85
  86         return 0;
  87 }
  88
  89 static int rt_timer_enable(struct rt_timer *rt)
  90 {
  91         u32 t;
  92
  93         rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div);
  94
  95         t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
  96         t |= TMR0CTL_ENABLE;
  97         rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
  98
  99         return 0;
 100 }
 101
 102 static void rt_timer_disable(struct rt_timer *rt)
 103 {
 104         u32 t;
 105
 106         t = rt_timer_r32(rt, TIMER_REG_TMR0CTL);
 107         t &= ~TMR0CTL_ENABLE;
 108         rt_timer_w32(rt, TIMER_REG_TMR0CTL, t);
 109 }
 110
 111 static int rt_timer_probe(struct platform_device *pdev)
 112 {
 113         struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 114         struct rt_timer *rt;
 115         struct clk *clk;
 116
 117         rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL);
 118         if (!rt) {
 119                 dev_err(&pdev->dev, "failed to allocate memory\n");
 120                 return -ENOMEM;
 121         }
 122
 123         rt->irq = platform_get_irq(pdev, 0);
 124         if (!rt->irq) {
 125                 dev_err(&pdev->dev, "failed to load irq\n");
 126                 return -ENOENT;
 127         }
 128
 129         rt->membase = devm_ioremap_resource(&pdev->dev, res);
 130         if (IS_ERR(rt->membase))
 131                 return PTR_ERR(rt->membase);
 132
 133         clk = devm_clk_get(&pdev->dev, NULL);
 134         if (IS_ERR(clk)) {
 135                 dev_err(&pdev->dev, "failed get clock rate\n");
 136                 return PTR_ERR(clk);
 137         }
 138
 139         rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV;
 140         if (!rt->timer_freq)
 141                 return -EINVAL;
 142
 143         rt->dev = &pdev->dev;
 144         platform_set_drvdata(pdev, rt);
 145
 146         rt_timer_request(rt);
 147         rt_timer_config(rt, 2);
 148         rt_timer_enable(rt);
 149
 150         dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq);
 151
 152         return 0;
 153 }
 154
 155 static int rt_timer_remove(struct platform_device *pdev)
 156 {
 157         struct rt_timer *rt = platform_get_drvdata(pdev);
 158
 159         rt_timer_disable(rt);
 160         rt_timer_free(rt);
 161
 162         return 0;
 163 }
 164
 165 static const struct of_device_id rt_timer_match[] = {
 166         { .compatible = "ralink,rt2880-timer" },
 167         {},
 168 };
 169 MODULE_DEVICE_TABLE(of, rt_timer_match);
 170
 171 static struct platform_driver rt_timer_driver = {
 172         .probe = rt_timer_probe,
 173         .remove = rt_timer_remove,
 174         .driver = {
 175                 .name           = "rt-timer",
 176                 .of_match_table = rt_timer_match
 177         },
 178 };
 179
 180 module_platform_driver(rt_timer_driver);
 181
 182 MODULE_DESCRIPTION("Ralink RT2880 timer");
 183 MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
 184 MODULE_LICENSE("GPL");