1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/kernel.h> 3 #include <linux/init.h> 4 #include <linux/clocksource.h> 5 #include <linux/clockchips.h> 6 #include <linux/sched_clock.h> 7 #include <linux/interrupt.h> 8 #include <linux/irq.h> 9 #include <linux/io.h> 10 #include <asm/mach/time.h> 11 #include "soc.h" 12 13 /************************************************************************* 14 * Timer handling for EP93xx 15 ************************************************************************* 16 * The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and 17 * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate 18 * an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz, 19 * is free-running, and can't generate interrupts. 20 * 21 * The 508 kHz timers are ideal for use for the timer interrupt, as the 22 * most common values of HZ divide 508 kHz nicely. We pick the 32 bit 23 * timer (timer 3) to get as long sleep intervals as possible when using 24 * CONFIG_NO_HZ. 25 * 26 * The higher clock rate of timer 4 makes it a better choice than the 27 * other timers for use as clock source and for sched_clock(), providing 28 * a stable 40 bit time base. 29 ************************************************************************* 30 */ 31 #define EP93XX_TIMER_REG(x) (EP93XX_TIMER_BASE + (x)) 32 #define EP93XX_TIMER1_LOAD EP93XX_TIMER_REG(0x00) 33 #define EP93XX_TIMER1_VALUE EP93XX_TIMER_REG(0x04) 34 #define EP93XX_TIMER1_CONTROL EP93XX_TIMER_REG(0x08) 35 #define EP93XX_TIMER123_CONTROL_ENABLE (1 << 7) 36 #define EP93XX_TIMER123_CONTROL_MODE (1 << 6) 37 #define EP93XX_TIMER123_CONTROL_CLKSEL (1 << 3) 38 #define EP93XX_TIMER1_CLEAR EP93XX_TIMER_REG(0x0c) 39 #define EP93XX_TIMER2_LOAD EP93XX_TIMER_REG(0x20) 40 #define EP93XX_TIMER2_VALUE EP93XX_TIMER_REG(0x24) 41 #define EP93XX_TIMER2_CONTROL EP93XX_TIMER_REG(0x28) 42 #define EP93XX_TIMER2_CLEAR EP93XX_TIMER_REG(0x2c) 43 #define EP93XX_TIMER4_VALUE_LOW EP93XX_TIMER_REG(0x60) 44 #define EP93XX_TIMER4_VALUE_HIGH EP93XX_TIMER_REG(0x64) 45 #define EP93XX_TIMER4_VALUE_HIGH_ENABLE (1 << 8) 46 #define EP93XX_TIMER3_LOAD EP93XX_TIMER_REG(0x80) 47 #define EP93XX_TIMER3_VALUE EP93XX_TIMER_REG(0x84) 48 #define EP93XX_TIMER3_CONTROL EP93XX_TIMER_REG(0x88) 49 #define EP93XX_TIMER3_CLEAR EP93XX_TIMER_REG(0x8c) 50 51 #define EP93XX_TIMER123_RATE 508469 52 #define EP93XX_TIMER4_RATE 983040 53 54 static u64 notrace ep93xx_read_sched_clock(void) 55 { 56 u64 ret; 57 58 ret = readl(EP93XX_TIMER4_VALUE_LOW); 59 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32); 60 return ret; 61 } 62 63 u64 ep93xx_clocksource_read(struct clocksource *c) 64 { 65 u64 ret; 66 67 ret = readl(EP93XX_TIMER4_VALUE_LOW); 68 ret |= ((u64) (readl(EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32); 69 return (u64) ret; 70 } 71 72 static int ep93xx_clkevt_set_next_event(unsigned long next, 73 struct clock_event_device *evt) 74 { 75 /* Default mode: periodic, off, 508 kHz */ 76 u32 tmode = EP93XX_TIMER123_CONTROL_MODE | 77 EP93XX_TIMER123_CONTROL_CLKSEL; 78 79 /* Clear timer */ 80 writel(tmode, EP93XX_TIMER3_CONTROL); 81 82 /* Set next event */ 83 writel(next, EP93XX_TIMER3_LOAD); 84 writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE, 85 EP93XX_TIMER3_CONTROL); 86 return 0; 87 } 88 89 90 static int ep93xx_clkevt_shutdown(struct clock_event_device *evt) 91 { 92 /* Disable timer */ 93 writel(0, EP93XX_TIMER3_CONTROL); 94 95 return 0; 96 } 97 98 static struct clock_event_device ep93xx_clockevent = { 99 .name = "timer1", 100 .features = CLOCK_EVT_FEAT_ONESHOT, 101 .set_state_shutdown = ep93xx_clkevt_shutdown, 102 .set_state_oneshot = ep93xx_clkevt_shutdown, 103 .tick_resume = ep93xx_clkevt_shutdown, 104 .set_next_event = ep93xx_clkevt_set_next_event, 105 .rating = 300, 106 }; 107 108 static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id) 109 { 110 struct clock_event_device *evt = dev_id; 111 112 /* Writing any value clears the timer interrupt */ 113 writel(1, EP93XX_TIMER3_CLEAR); 114 115 evt->event_handler(evt); 116 117 return IRQ_HANDLED; 118 } 119 120 void __init ep93xx_timer_init(void) 121 { 122 int irq = IRQ_EP93XX_TIMER3; 123 unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL; 124 125 /* Enable and register clocksource and sched_clock on timer 4 */ 126 writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE, 127 EP93XX_TIMER4_VALUE_HIGH); 128 clocksource_mmio_init(NULL, "timer4", 129 EP93XX_TIMER4_RATE, 200, 40, 130 ep93xx_clocksource_read); 131 sched_clock_register(ep93xx_read_sched_clock, 40, 132 EP93XX_TIMER4_RATE); 133 134 /* Set up clockevent on timer 3 */ 135 if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer", 136 &ep93xx_clockevent)) 137 pr_err("Failed to request irq %d (ep93xx timer)\n", irq); 138 clockevents_config_and_register(&ep93xx_clockevent, 139 EP93XX_TIMER123_RATE, 140 1, 141 0xffffffffU); 142 } 143