drivers/clocksource/clksrc_st_lpc.c

   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 – 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
  25 static struct st_clksrc_ddata {
  26         struct clk              *clk;
  27         void __iomem            *base;
  28 } ddata;
  29
  30 static 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
  38 static u64 notrace st_clksrc_sched_clock_read(void)
  39 {
  40         return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
  41 }
  42
  43 static 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
  65 static 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
  91 static 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 }
 131 TIMER_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);