1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) ST-Ericsson SA 2011 4 * 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 19 #define RATE_32K 32768 20 21 #define TIMER_MODE_CONTINOUS 0x1 22 #define TIMER_DOWNCOUNT_VAL 0xffffffff 23 24 #define PRCMU_TIMER_REF 0 25 #define PRCMU_TIMER_DOWNCOUNT 0x4 26 #define PRCMU_TIMER_MODE 0x8 27 28 static void __iomem *clksrc_dbx500_timer_base; 29 30 static u64 notrace clksrc_dbx500_prcmu_read(struct clocksource *cs) 31 { 32 void __iomem *base = clksrc_dbx500_timer_base; 33 u32 count, count2; 34 35 do { 36 count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT); 37 count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT); 38 } while (count2 != count); 39 40 /* Negate because the timer is a decrementing counter */ 41 return ~count; 42 } 43 44 static struct clocksource clocksource_dbx500_prcmu = { 45 .name = "dbx500-prcmu-timer", 46 .rating = 100, 47 .read = clksrc_dbx500_prcmu_read, 48 .mask = CLOCKSOURCE_MASK(32), 49 .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP, 50 }; 51 52 static int __init clksrc_dbx500_prcmu_init(struct device_node *node) 53 { 54 clksrc_dbx500_timer_base = of_iomap(node, 0); 55 56 /* 57 * The A9 sub system expects the timer to be configured as 58 * a continous looping timer. 59 * The PRCMU should configure it but if it for some reason 60 * don't we do it here. 61 */ 62 if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) != 63 TIMER_MODE_CONTINOUS) { 64 writel(TIMER_MODE_CONTINOUS, 65 clksrc_dbx500_timer_base + PRCMU_TIMER_MODE); 66 writel(TIMER_DOWNCOUNT_VAL, 67 clksrc_dbx500_timer_base + PRCMU_TIMER_REF); 68 } 69 return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K); 70 } 71 TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4", 72 clksrc_dbx500_prcmu_init); 73