1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/types.h> 3 #include <linux/i8253.h> 4 #include <linux/interrupt.h> 5 #include <linux/irq.h> 6 #include <linux/smp.h> 7 #include <linux/time.h> 8 #include <linux/clockchips.h> 9 10 #include <asm/sni.h> 11 #include <asm/time.h> 12 13 #define SNI_CLOCK_TICK_RATE 3686400 14 #define SNI_COUNTER2_DIV 64 15 #define SNI_COUNTER0_DIV ((SNI_CLOCK_TICK_RATE / SNI_COUNTER2_DIV) / HZ) 16 17 static int a20r_set_periodic(struct clock_event_device *evt) 18 { 19 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0x34; 20 wmb(); 21 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV; 22 wmb(); 23 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 0) = SNI_COUNTER0_DIV >> 8; 24 wmb(); 25 26 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 12) = 0xb4; 27 wmb(); 28 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV; 29 wmb(); 30 *(volatile u8 *)(A20R_PT_CLOCK_BASE + 8) = SNI_COUNTER2_DIV >> 8; 31 wmb(); 32 return 0; 33 } 34 35 static struct clock_event_device a20r_clockevent_device = { 36 .name = "a20r-timer", 37 .features = CLOCK_EVT_FEAT_PERIODIC, 38 39 /* .mult, .shift, .max_delta_ns and .min_delta_ns left uninitialized */ 40 41 .rating = 300, 42 .irq = SNI_A20R_IRQ_TIMER, 43 .set_state_periodic = a20r_set_periodic, 44 }; 45 46 static irqreturn_t a20r_interrupt(int irq, void *dev_id) 47 { 48 struct clock_event_device *cd = dev_id; 49 50 *(volatile u8 *)A20R_PT_TIM0_ACK = 0; 51 wmb(); 52 53 cd->event_handler(cd); 54 55 return IRQ_HANDLED; 56 } 57 58 /* 59 * a20r platform uses 2 counters to divide the input frequency. 60 * Counter 2 output is connected to Counter 0 & 1 input. 61 */ 62 static void __init sni_a20r_timer_setup(void) 63 { 64 struct clock_event_device *cd = &a20r_clockevent_device; 65 unsigned int cpu = smp_processor_id(); 66 67 cd->cpumask = cpumask_of(cpu); 68 clockevents_register_device(cd); 69 if (request_irq(SNI_A20R_IRQ_TIMER, a20r_interrupt, 70 IRQF_PERCPU | IRQF_TIMER, "a20r-timer", cd)) 71 pr_err("Failed to register a20r-timer interrupt\n"); 72 } 73 74 #define SNI_8254_TICK_RATE 1193182UL 75 76 #define SNI_8254_TCSAMP_COUNTER ((SNI_8254_TICK_RATE / HZ) + 255) 77 78 static __init unsigned long dosample(void) 79 { 80 u32 ct0, ct1; 81 volatile u8 msb; 82 83 /* Start the counter. */ 84 outb_p(0x34, 0x43); 85 outb_p(SNI_8254_TCSAMP_COUNTER & 0xff, 0x40); 86 outb(SNI_8254_TCSAMP_COUNTER >> 8, 0x40); 87 88 /* Get initial counter invariant */ 89 ct0 = read_c0_count(); 90 91 /* Latch and spin until top byte of counter0 is zero */ 92 do { 93 outb(0x00, 0x43); 94 (void) inb(0x40); 95 msb = inb(0x40); 96 ct1 = read_c0_count(); 97 } while (msb); 98 99 /* Stop the counter. */ 100 outb(0x38, 0x43); 101 /* 102 * Return the difference, this is how far the r4k counter increments 103 * for every 1/HZ seconds. We round off the nearest 1 MHz of master 104 * clock (= 1000000 / HZ / 2). 105 */ 106 /*return (ct1 - ct0 + (500000/HZ/2)) / (500000/HZ) * (500000/HZ);*/ 107 return (ct1 - ct0) / (500000/HZ) * (500000/HZ); 108 } 109 110 /* 111 * Here we need to calibrate the cycle counter to at least be close. 112 */ 113 void __init plat_time_init(void) 114 { 115 unsigned long r4k_ticks[3]; 116 unsigned long r4k_tick; 117 118 /* 119 * Figure out the r4k offset, the algorithm is very simple and works in 120 * _all_ cases as long as the 8254 counter register itself works ok (as 121 * an interrupt driving timer it does not because of bug, this is why 122 * we are using the onchip r4k counter/compare register to serve this 123 * purpose, but for r4k_offset calculation it will work ok for us). 124 * There are other very complicated ways of performing this calculation 125 * but this one works just fine so I am not going to futz around. ;-) 126 */ 127 printk(KERN_INFO "Calibrating system timer... "); 128 dosample(); /* Prime cache. */ 129 dosample(); /* Prime cache. */ 130 /* Zero is NOT an option. */ 131 do { 132 r4k_ticks[0] = dosample(); 133 } while (!r4k_ticks[0]); 134 do { 135 r4k_ticks[1] = dosample(); 136 } while (!r4k_ticks[1]); 137 138 if (r4k_ticks[0] != r4k_ticks[1]) { 139 printk("warning: timer counts differ, retrying... "); 140 r4k_ticks[2] = dosample(); 141 if (r4k_ticks[2] == r4k_ticks[0] 142 || r4k_ticks[2] == r4k_ticks[1]) 143 r4k_tick = r4k_ticks[2]; 144 else { 145 printk("disagreement, using average... "); 146 r4k_tick = (r4k_ticks[0] + r4k_ticks[1] 147 + r4k_ticks[2]) / 3; 148 } 149 } else 150 r4k_tick = r4k_ticks[0]; 151 152 printk("%d [%d.%04d MHz CPU]\n", (int) r4k_tick, 153 (int) (r4k_tick / (500000 / HZ)), 154 (int) (r4k_tick % (500000 / HZ))); 155 156 mips_hpt_frequency = r4k_tick * HZ; 157 158 switch (sni_brd_type) { 159 case SNI_BRD_10: 160 case SNI_BRD_10NEW: 161 case SNI_BRD_TOWER_OASIC: 162 case SNI_BRD_MINITOWER: 163 sni_a20r_timer_setup(); 164 break; 165 } 166 setup_pit_timer(); 167 } 168