linux/drivers/clocksource/clksrc_st_lpc.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
   4 *
   5 * Copyright (C) 2015 STMicroelectronics \xE2\x80\x93 All Rights Reserved
   6 *
   7 * Author(s): Francesco Virlinzi <francesco.virlinzi@st.com>
   8 *            Ajit Pal Singh <ajitpal.singh@st.com>
   9 */
  10
  11#include <linux/clk.h>
  12#include <linux/clocksource.h>
  13#include <linux/init.h>
  14#include <linux/of_address.h>
  15#include <linux/sched_clock.h>
  16#include <linux/slab.h>
  17
  18#include <dt-bindings/mfd/st-lpc.h>
  19
  20/* Low Power Timer */
  21#define LPC_LPT_LSB_OFF         0x400
  22#define LPC_LPT_MSB_OFF         0x404
  23#define LPC_LPT_START_OFF       0x408
  24
  25static struct st_clksrc_ddata {
  26        struct clk              *clk;
  27        void __iomem            *base;
  28} ddata;
  29
  30static void __init st_clksrc_reset(void)
  31{
  32        writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
  33        writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
  34        writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
  35        writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
  36}
  37
  38static u64 notrace st_clksrc_sched_clock_read(void)
  39{
  40        return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
  41}
  42
  43static int __init st_clksrc_init(void)
  44{
  45        unsigned long rate;
  46        int ret;
  47
  48        st_clksrc_reset();
  49
  50        rate = clk_get_rate(ddata.clk);
  51
  52        sched_clock_register(st_clksrc_sched_clock_read, 32, rate);
  53
  54        ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
  55                                    "clksrc-st-lpc", rate, 300, 32,
  56                                    clocksource_mmio_readl_up);
  57        if (ret) {
  58                pr_err("clksrc-st-lpc: Failed to register clocksource\n");
  59                return ret;
  60        }
  61
  62        return 0;
  63}
  64
  65static int __init st_clksrc_setup_clk(struct device_node *np)
  66{
  67        struct clk *clk;
  68
  69        clk = of_clk_get(np, 0);
  70        if (IS_ERR(clk)) {
  71                pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
  72                return PTR_ERR(clk);
  73        }
  74
  75        if (clk_prepare_enable(clk)) {
  76                pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
  77                return -EINVAL;
  78        }
  79
  80        if (!clk_get_rate(clk)) {
  81                pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
  82                clk_disable_unprepare(clk);
  83                return -EINVAL;
  84        }
  85
  86        ddata.clk = clk;
  87
  88        return 0;
  89}
  90
  91static int __init st_clksrc_of_register(struct device_node *np)
  92{
  93        int ret;
  94        uint32_t mode;
  95
  96        ret = of_property_read_u32(np, "st,lpc-mode", &mode);
  97        if (ret) {
  98                pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
  99                return ret;
 100        }
 101
 102        /* LPC can either run as a Clocksource or in RTC or WDT mode */
 103        if (mode != ST_LPC_MODE_CLKSRC)
 104                return 0;
 105
 106        ddata.base = of_iomap(np, 0);
 107        if (!ddata.base) {
 108                pr_err("clksrc-st-lpc: Unable to map iomem\n");
 109                return -ENXIO;
 110        }
 111
 112        ret = st_clksrc_setup_clk(np);
 113        if (ret) {
 114                iounmap(ddata.base);
 115                return ret;
 116        }
 117
 118        ret = st_clksrc_init();
 119        if (ret) {
 120                clk_disable_unprepare(ddata.clk);
 121                clk_put(ddata.clk);
 122                iounmap(ddata.base);
 123                return ret;
 124        }
 125
 126        pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
 127                clk_get_rate(ddata.clk));
 128
 129        return ret;
 130}
 131TIMER_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);
 132