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Linux/arch/mips/ralink/timer.c

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  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, IRQF_DISABLED,
 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                 .owner          = THIS_MODULE,
177                 .of_match_table = rt_timer_match
178         },
179 };
180 
181 module_platform_driver(rt_timer_driver);
182 
183 MODULE_DESCRIPTION("Ralink RT2880 timer");
184 MODULE_AUTHOR("John Crispin <blogic@openwrt.org");
185 MODULE_LICENSE("GPL");
186 

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