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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright (C) ST-Ericsson SA 20114 *5 * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson6 * Author: Sundar Iyer for ST-Ericsson7 * sched_clock implementation is based on:8 * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>9 *10 * DBx500-PRCMU Timer11 * The PRCMU has 5 timers which are available in a always-on12 * power domain. We use the Timer 4 for our always-on clock13 * 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 3276820 21#define TIMER_MODE_CONTINUOUS 0x122#define TIMER_DOWNCOUNT_VAL 0xffffffff23 24#define PRCMU_TIMER_REF 025#define PRCMU_TIMER_DOWNCOUNT 0x426#define PRCMU_TIMER_MODE 0x827 28static void __iomem *clksrc_dbx500_timer_base;29 30static 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 44static 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 52static 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 as58 * a continuous looping timer.59 * The PRCMU should configure it but if it for some reason60 * don't we do it here.61 */62 if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=63 TIMER_MODE_CONTINUOUS) {64 writel(TIMER_MODE_CONTINUOUS,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}71TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",72 clksrc_dbx500_prcmu_init);73