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 void rt_timer_free(struct rt_timer *rt) 75 { 76 free_irq(rt->irq, rt); 77 } 78 79 static int rt_timer_config(struct rt_timer *rt, unsigned long divisor) 80 { 81 if (rt->timer_freq < divisor) 82 rt->timer_div = rt->timer_freq; 83 else 84 rt->timer_div = divisor; 85 86 rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div); 87 88 return 0; 89 } 90 91 static int rt_timer_enable(struct rt_timer *rt) 92 { 93 u32 t; 94 95 rt_timer_w32(rt, TIMER_REG_TMR0LOAD, rt->timer_freq / rt->timer_div); 96 97 t = rt_timer_r32(rt, TIMER_REG_TMR0CTL); 98 t |= TMR0CTL_ENABLE; 99 rt_timer_w32(rt, TIMER_REG_TMR0CTL, t); 100 101 return 0; 102 } 103 104 static void rt_timer_disable(struct rt_timer *rt) 105 { 106 u32 t; 107 108 t = rt_timer_r32(rt, TIMER_REG_TMR0CTL); 109 t &= ~TMR0CTL_ENABLE; 110 rt_timer_w32(rt, TIMER_REG_TMR0CTL, t); 111 } 112 113 static int rt_timer_probe(struct platform_device *pdev) 114 { 115 struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 116 struct rt_timer *rt; 117 struct clk *clk; 118 119 rt = devm_kzalloc(&pdev->dev, sizeof(*rt), GFP_KERNEL); 120 if (!rt) { 121 dev_err(&pdev->dev, "failed to allocate memory\n"); 122 return -ENOMEM; 123 } 124 125 rt->irq = platform_get_irq(pdev, 0); 126 if (!rt->irq) { 127 dev_err(&pdev->dev, "failed to load irq\n"); 128 return -ENOENT; 129 } 130 131 rt->membase = devm_ioremap_resource(&pdev->dev, res); 132 if (IS_ERR(rt->membase)) 133 return PTR_ERR(rt->membase); 134 135 clk = devm_clk_get(&pdev->dev, NULL); 136 if (IS_ERR(clk)) { 137 dev_err(&pdev->dev, "failed get clock rate\n"); 138 return PTR_ERR(clk); 139 } 140 141 rt->timer_freq = clk_get_rate(clk) / TMR0CTL_PRESCALE_DIV; 142 if (!rt->timer_freq) 143 return -EINVAL; 144 145 rt->dev = &pdev->dev; 146 platform_set_drvdata(pdev, rt); 147 148 rt_timer_request(rt); 149 rt_timer_config(rt, 2); 150 rt_timer_enable(rt); 151 152 dev_info(&pdev->dev, "maximum frequency is %luHz\n", rt->timer_freq); 153 154 return 0; 155 } 156 157 static const struct of_device_id rt_timer_match[] = { 158 { .compatible = "ralink,rt2880-timer" }, 159 {}, 160 }; 161 162 static struct platform_driver rt_timer_driver = { 163 .probe = rt_timer_probe, 164 .driver = { 165 .name = "rt-timer", 166 .of_match_table = rt_timer_match, 167 .suppress_bind_attrs = true, 168 }, 169 }; 170 builtin_platform_driver(rt_timer_driver); 171