arch/arm/mach-ep93xx/timer-ep93xx.c

   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 }