arch/mips/ralink/timer.c

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