1 /* 2 * Copyright (C) ST-Ericsson SA 2011 3 * 4 * License Terms: GNU General Public License v2 5 * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson 6 * Author: Sundar Iyer for ST-Ericsson 7 * sched_clock implementation is based on: 8 * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com> 9 * 10 * DBx500-PRCMU Timer 11 * The PRCMU has 5 timers which are available in a always-on 12 * power domain. We use the Timer 4 for our always-on clock 13 * source on DB8500. 14 */ 15 #include <linux/of.h> 16 #include <linux/of_address.h> 17 #include <linux/clockchips.h> 18 #include <linux/sched_clock.h> 19 20 #define RATE_32K 32768 21 22 #define TIMER_MODE_CONTINOUS 0x1 23 #define TIMER_DOWNCOUNT_VAL 0xffffffff 24 25 #define PRCMU_TIMER_REF 0 26 #define PRCMU_TIMER_DOWNCOUNT 0x4 27 #define PRCMU_TIMER_MODE 0x8 28 29 #define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */ 30 31 static void __iomem *clksrc_dbx500_timer_base; 32 33 static u64 notrace clksrc_dbx500_prcmu_read(struct clocksource *cs) 34 { 35 void __iomem *base = clksrc_dbx500_timer_base; 36 u32 count, count2; 37 38 do { 39 count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT); 40 count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT); 41 } while (count2 != count); 42 43 /* Negate because the timer is a decrementing counter */ 44 return ~count; 45 } 46 47 static struct clocksource clocksource_dbx500_prcmu = { 48 .name = "dbx500-prcmu-timer", 49 .rating = 300, 50 .read = clksrc_dbx500_prcmu_read, 51 .mask = CLOCKSOURCE_MASK(32), 52 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 53 }; 54 55 #ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK 56 57 static u64 notrace dbx500_prcmu_sched_clock_read(void) 58 { 59 if (unlikely(!clksrc_dbx500_timer_base)) 60 return 0; 61 62 return clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu); 63 } 64 65 #endif 66 67 static int __init clksrc_dbx500_prcmu_init(struct device_node *node) 68 { 69 clksrc_dbx500_timer_base = of_iomap(node, 0); 70 71 /* 72 * The A9 sub system expects the timer to be configured as 73 * a continous looping timer. 74 * The PRCMU should configure it but if it for some reason 75 * don't we do it here. 76 */ 77 if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) != 78 TIMER_MODE_CONTINOUS) { 79 writel(TIMER_MODE_CONTINOUS, 80 clksrc_dbx500_timer_base + PRCMU_TIMER_MODE); 81 writel(TIMER_DOWNCOUNT_VAL, 82 clksrc_dbx500_timer_base + PRCMU_TIMER_REF); 83 } 84 #ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK 85 sched_clock_register(dbx500_prcmu_sched_clock_read, 32, RATE_32K); 86 #endif 87 return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K); 88 } 89 CLOCKSOURCE_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4", 90 clksrc_dbx500_prcmu_init); 91