1 /* 2 * Copyright (C) 2012 Broadcom Corporation 3 * 4 * This program is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License as 6 * published by the Free Software Foundation version 2. 7 * 8 * This program is distributed "as is" WITHOUT ANY WARRANTY of any 9 * kind, whether express or implied; without even the implied warranty 10 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 * GNU General Public License for more details. 12 */ 13 14 #include <linux/init.h> 15 #include <linux/irq.h> 16 #include <linux/interrupt.h> 17 #include <linux/jiffies.h> 18 #include <linux/clockchips.h> 19 #include <linux/types.h> 20 #include <linux/clk.h> 21 22 #include <linux/io.h> 23 24 #include <linux/of.h> 25 #include <linux/of_address.h> 26 #include <linux/of_irq.h> 27 28 29 #define KONA_GPTIMER_STCS_OFFSET 0x00000000 30 #define KONA_GPTIMER_STCLO_OFFSET 0x00000004 31 #define KONA_GPTIMER_STCHI_OFFSET 0x00000008 32 #define KONA_GPTIMER_STCM0_OFFSET 0x0000000C 33 34 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT 0 35 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT 4 36 37 struct kona_bcm_timers { 38 int tmr_irq; 39 void __iomem *tmr_regs; 40 }; 41 42 static struct kona_bcm_timers timers; 43 44 static u32 arch_timer_rate; 45 46 /* 47 * We use the peripheral timers for system tick, the cpu global timer for 48 * profile tick 49 */ 50 static void kona_timer_disable_and_clear(void __iomem *base) 51 { 52 uint32_t reg; 53 54 /* 55 * clear and disable interrupts 56 * We are using compare/match register 0 for our system interrupts 57 */ 58 reg = readl(base + KONA_GPTIMER_STCS_OFFSET); 59 60 /* Clear compare (0) interrupt */ 61 reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT; 62 /* disable compare */ 63 reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); 64 65 writel(reg, base + KONA_GPTIMER_STCS_OFFSET); 66 67 } 68 69 static int 70 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw) 71 { 72 int loop_limit = 3; 73 74 /* 75 * Read 64-bit free running counter 76 * 1. Read hi-word 77 * 2. Read low-word 78 * 3. Read hi-word again 79 * 4.1 80 * if new hi-word is not equal to previously read hi-word, then 81 * start from #1 82 * 4.2 83 * if new hi-word is equal to previously read hi-word then stop. 84 */ 85 86 do { 87 *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET); 88 *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET); 89 if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET)) 90 break; 91 } while (--loop_limit); 92 if (!loop_limit) { 93 pr_err("bcm_kona_timer: getting counter failed.\n"); 94 pr_err(" Timer will be impacted\n"); 95 return -ETIMEDOUT; 96 } 97 98 return 0; 99 } 100 101 static int kona_timer_set_next_event(unsigned long clc, 102 struct clock_event_device *unused) 103 { 104 /* 105 * timer (0) is disabled by the timer interrupt already 106 * so, here we reload the next event value and re-enable 107 * the timer. 108 * 109 * This way, we are potentially losing the time between 110 * timer-interrupt->set_next_event. CPU local timers, when 111 * they come in should get rid of skew. 112 */ 113 114 uint32_t lsw, msw; 115 uint32_t reg; 116 int ret; 117 118 ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw); 119 if (ret) 120 return ret; 121 122 /* Load the "next" event tick value */ 123 writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET); 124 125 /* Enable compare */ 126 reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); 127 reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); 128 writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); 129 130 return 0; 131 } 132 133 static int kona_timer_shutdown(struct clock_event_device *evt) 134 { 135 kona_timer_disable_and_clear(timers.tmr_regs); 136 return 0; 137 } 138 139 static struct clock_event_device kona_clockevent_timer = { 140 .name = "timer 1", 141 .features = CLOCK_EVT_FEAT_ONESHOT, 142 .set_next_event = kona_timer_set_next_event, 143 .set_state_shutdown = kona_timer_shutdown, 144 .tick_resume = kona_timer_shutdown, 145 }; 146 147 static void __init kona_timer_clockevents_init(void) 148 { 149 kona_clockevent_timer.cpumask = cpumask_of(0); 150 clockevents_config_and_register(&kona_clockevent_timer, 151 arch_timer_rate, 6, 0xffffffff); 152 } 153 154 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id) 155 { 156 struct clock_event_device *evt = &kona_clockevent_timer; 157 158 kona_timer_disable_and_clear(timers.tmr_regs); 159 evt->event_handler(evt); 160 return IRQ_HANDLED; 161 } 162 163 static int __init kona_timer_init(struct device_node *node) 164 { 165 u32 freq; 166 struct clk *external_clk; 167 168 external_clk = of_clk_get_by_name(node, NULL); 169 170 if (!IS_ERR(external_clk)) { 171 arch_timer_rate = clk_get_rate(external_clk); 172 clk_prepare_enable(external_clk); 173 } else if (!of_property_read_u32(node, "clock-frequency", &freq)) { 174 arch_timer_rate = freq; 175 } else { 176 pr_err("Kona Timer v1 unable to determine clock-frequency\n"); 177 return -EINVAL; 178 } 179 180 /* Setup IRQ numbers */ 181 timers.tmr_irq = irq_of_parse_and_map(node, 0); 182 183 /* Setup IO addresses */ 184 timers.tmr_regs = of_iomap(node, 0); 185 186 kona_timer_disable_and_clear(timers.tmr_regs); 187 188 kona_timer_clockevents_init(); 189 if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER, 190 "Kona Timer Tick", NULL)) 191 pr_err("%s: request_irq() failed\n", "Kona Timer Tick"); 192 kona_timer_set_next_event((arch_timer_rate / HZ), NULL); 193 194 return 0; 195 } 196 197 TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init); 198 /* 199 * bcm,kona-timer is deprecated by brcm,kona-timer 200 * being kept here for driver compatibility 201 */ 202 TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init); 203