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 #include <asm/mach/time.h> 24 25 #include <linux/of.h> 26 #include <linux/of_address.h> 27 #include <linux/of_irq.h> 28 29 30 #define KONA_GPTIMER_STCS_OFFSET 0x00000000 31 #define KONA_GPTIMER_STCLO_OFFSET 0x00000004 32 #define KONA_GPTIMER_STCHI_OFFSET 0x00000008 33 #define KONA_GPTIMER_STCM0_OFFSET 0x0000000C 34 35 #define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT 0 36 #define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT 4 37 38 struct kona_bcm_timers { 39 int tmr_irq; 40 void __iomem *tmr_regs; 41 }; 42 43 static struct kona_bcm_timers timers; 44 45 static u32 arch_timer_rate; 46 47 /* 48 * We use the peripheral timers for system tick, the cpu global timer for 49 * profile tick 50 */ 51 static void kona_timer_disable_and_clear(void __iomem *base) 52 { 53 uint32_t reg; 54 55 /* 56 * clear and disable interrupts 57 * We are using compare/match register 0 for our system interrupts 58 */ 59 reg = readl(base + KONA_GPTIMER_STCS_OFFSET); 60 61 /* Clear compare (0) interrupt */ 62 reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT; 63 /* disable compare */ 64 reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); 65 66 writel(reg, base + KONA_GPTIMER_STCS_OFFSET); 67 68 } 69 70 static void 71 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw) 72 { 73 int loop_limit = 4; 74 75 /* 76 * Read 64-bit free running counter 77 * 1. Read hi-word 78 * 2. Read low-word 79 * 3. Read hi-word again 80 * 4.1 81 * if new hi-word is not equal to previously read hi-word, then 82 * start from #1 83 * 4.2 84 * if new hi-word is equal to previously read hi-word then stop. 85 */ 86 87 while (--loop_limit) { 88 *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET); 89 *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET); 90 if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET)) 91 break; 92 } 93 if (!loop_limit) { 94 pr_err("bcm_kona_timer: getting counter failed.\n"); 95 pr_err(" Timer will be impacted\n"); 96 } 97 98 return; 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; 116 117 kona_timer_get_counter(timers.tmr_regs, &msw, &lsw); 118 119 /* Load the "next" event tick value */ 120 writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET); 121 122 /* Enable compare */ 123 reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); 124 reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); 125 writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); 126 127 return 0; 128 } 129 130 static int kona_timer_shutdown(struct clock_event_device *evt) 131 { 132 kona_timer_disable_and_clear(timers.tmr_regs); 133 return 0; 134 } 135 136 static struct clock_event_device kona_clockevent_timer = { 137 .name = "timer 1", 138 .features = CLOCK_EVT_FEAT_ONESHOT, 139 .set_next_event = kona_timer_set_next_event, 140 .set_state_shutdown = kona_timer_shutdown, 141 .tick_resume = kona_timer_shutdown, 142 }; 143 144 static void __init kona_timer_clockevents_init(void) 145 { 146 kona_clockevent_timer.cpumask = cpumask_of(0); 147 clockevents_config_and_register(&kona_clockevent_timer, 148 arch_timer_rate, 6, 0xffffffff); 149 } 150 151 static irqreturn_t kona_timer_interrupt(int irq, void *dev_id) 152 { 153 struct clock_event_device *evt = &kona_clockevent_timer; 154 155 kona_timer_disable_and_clear(timers.tmr_regs); 156 evt->event_handler(evt); 157 return IRQ_HANDLED; 158 } 159 160 static struct irqaction kona_timer_irq = { 161 .name = "Kona Timer Tick", 162 .flags = IRQF_TIMER, 163 .handler = kona_timer_interrupt, 164 }; 165 166 static void __init kona_timer_init(struct device_node *node) 167 { 168 u32 freq; 169 struct clk *external_clk; 170 171 if (!of_device_is_available(node)) { 172 pr_info("Kona Timer v1 marked as disabled in device tree\n"); 173 return; 174 } 175 176 external_clk = of_clk_get_by_name(node, NULL); 177 178 if (!IS_ERR(external_clk)) { 179 arch_timer_rate = clk_get_rate(external_clk); 180 clk_prepare_enable(external_clk); 181 } else if (!of_property_read_u32(node, "clock-frequency", &freq)) { 182 arch_timer_rate = freq; 183 } else { 184 pr_err("Kona Timer v1 unable to determine clock-frequency"); 185 return; 186 } 187 188 /* Setup IRQ numbers */ 189 timers.tmr_irq = irq_of_parse_and_map(node, 0); 190 191 /* Setup IO addresses */ 192 timers.tmr_regs = of_iomap(node, 0); 193 194 kona_timer_disable_and_clear(timers.tmr_regs); 195 196 kona_timer_clockevents_init(); 197 setup_irq(timers.tmr_irq, &kona_timer_irq); 198 kona_timer_set_next_event((arch_timer_rate / HZ), NULL); 199 } 200 201 CLOCKSOURCE_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init); 202 /* 203 * bcm,kona-timer is deprecated by brcm,kona-timer 204 * being kept here for driver compatibility 205 */ 206 CLOCKSOURCE_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init); 207