drivers/clocksource/timer-pistachio.c

   1 /*
   2  * Pistachio clocksource based on general-purpose timers
   3  *
   4  * Copyright (C) 2015 Imagination Technologies
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License. See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  */
  10
  11 #define pr_fmt(fmt) "%s: " fmt, __func__
  12
  13 #include <linux/clk.h>
  14 #include <linux/clocksource.h>
  15 #include <linux/clockchips.h>
  16 #include <linux/delay.h>
  17 #include <linux/err.h>
  18 #include <linux/init.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/mfd/syscon.h>
  21 #include <linux/of.h>
  22 #include <linux/of_address.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/regmap.h>
  25 #include <linux/sched_clock.h>
  26 #include <linux/time.h>
  27
  28 /* Top level reg */
  29 #define CR_TIMER_CTRL_CFG               0x00
  30 #define TIMER_ME_GLOBAL                 BIT(0)
  31 #define CR_TIMER_REV                    0x10
  32
  33 /* Timer specific registers */
  34 #define TIMER_CFG                       0x20
  35 #define TIMER_ME_LOCAL                  BIT(0)
  36 #define TIMER_RELOAD_VALUE              0x24
  37 #define TIMER_CURRENT_VALUE             0x28
  38 #define TIMER_CURRENT_OVERFLOW_VALUE    0x2C
  39 #define TIMER_IRQ_STATUS                0x30
  40 #define TIMER_IRQ_CLEAR                 0x34
  41 #define TIMER_IRQ_MASK                  0x38
  42
  43 #define PERIP_TIMER_CONTROL             0x90
  44
  45 /* Timer specific configuration Values */
  46 #define RELOAD_VALUE                    0xffffffff
  47
  48 struct pistachio_clocksource {
  49         void __iomem *base;
  50         raw_spinlock_t lock;
  51         struct clocksource cs;
  52 };
  53
  54 static struct pistachio_clocksource pcs_gpt;
  55
  56 #define to_pistachio_clocksource(cs)    \
  57         container_of(cs, struct pistachio_clocksource, cs)
  58
  59 static inline u32 gpt_readl(void __iomem *base, u32 offset, u32 gpt_id)
  60 {
  61         return readl(base + 0x20 * gpt_id + offset);
  62 }
  63
  64 static inline void gpt_writel(void __iomem *base, u32 value, u32 offset,
  65                 u32 gpt_id)
  66 {
  67         writel(value, base + 0x20 * gpt_id + offset);
  68 }
  69
  70 static u64 notrace
  71 pistachio_clocksource_read_cycles(struct clocksource *cs)
  72 {
  73         struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
  74         u32 counter, overflw;
  75         unsigned long flags;
  76
  77         /*
  78          * The counter value is only refreshed after the overflow value is read.
  79          * And they must be read in strict order, hence raw spin lock added.
  80          */
  81
  82         raw_spin_lock_irqsave(&pcs->lock, flags);
  83         overflw = gpt_readl(pcs->base, TIMER_CURRENT_OVERFLOW_VALUE, 0);
  84         counter = gpt_readl(pcs->base, TIMER_CURRENT_VALUE, 0);
  85         raw_spin_unlock_irqrestore(&pcs->lock, flags);
  86
  87         return (u64)~counter;
  88 }
  89
  90 static u64 notrace pistachio_read_sched_clock(void)
  91 {
  92         return pistachio_clocksource_read_cycles(&pcs_gpt.cs);
  93 }
  94
  95 static void pistachio_clksrc_set_mode(struct clocksource *cs, int timeridx,
  96                         int enable)
  97 {
  98         struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
  99         u32 val;
 100
 101         val = gpt_readl(pcs->base, TIMER_CFG, timeridx);
 102         if (enable)
 103                 val |= TIMER_ME_LOCAL;
 104         else
 105                 val &= ~TIMER_ME_LOCAL;
 106
 107         gpt_writel(pcs->base, val, TIMER_CFG, timeridx);
 108 }
 109
 110 static void pistachio_clksrc_enable(struct clocksource *cs, int timeridx)
 111 {
 112         struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
 113
 114         /* Disable GPT local before loading reload value */
 115         pistachio_clksrc_set_mode(cs, timeridx, false);
 116         gpt_writel(pcs->base, RELOAD_VALUE, TIMER_RELOAD_VALUE, timeridx);
 117         pistachio_clksrc_set_mode(cs, timeridx, true);
 118 }
 119
 120 static void pistachio_clksrc_disable(struct clocksource *cs, int timeridx)
 121 {
 122         /* Disable GPT local */
 123         pistachio_clksrc_set_mode(cs, timeridx, false);
 124 }
 125
 126 static int pistachio_clocksource_enable(struct clocksource *cs)
 127 {
 128         pistachio_clksrc_enable(cs, 0);
 129         return 0;
 130 }
 131
 132 static void pistachio_clocksource_disable(struct clocksource *cs)
 133 {
 134         pistachio_clksrc_disable(cs, 0);
 135 }
 136
 137 /* Desirable clock source for pistachio platform */
 138 static struct pistachio_clocksource pcs_gpt = {
 139         .cs =   {
 140                 .name           = "gptimer",
 141                 .rating         = 300,
 142                 .enable         = pistachio_clocksource_enable,
 143                 .disable        = pistachio_clocksource_disable,
 144                 .read           = pistachio_clocksource_read_cycles,
 145                 .mask           = CLOCKSOURCE_MASK(32),
 146                 .flags          = CLOCK_SOURCE_IS_CONTINUOUS |
 147                                   CLOCK_SOURCE_SUSPEND_NONSTOP,
 148                 },
 149 };
 150
 151 static int __init pistachio_clksrc_of_init(struct device_node *node)
 152 {
 153         struct clk *sys_clk, *fast_clk;
 154         struct regmap *periph_regs;
 155         unsigned long rate;
 156         int ret;
 157
 158         pcs_gpt.base = of_iomap(node, 0);
 159         if (!pcs_gpt.base) {
 160                 pr_err("cannot iomap\n");
 161                 return -ENXIO;
 162         }
 163
 164         periph_regs = syscon_regmap_lookup_by_phandle(node, "img,cr-periph");
 165         if (IS_ERR(periph_regs)) {
 166                 pr_err("cannot get peripheral regmap (%ld)\n",
 167                        PTR_ERR(periph_regs));
 168                 return PTR_ERR(periph_regs);
 169         }
 170
 171         /* Switch to using the fast counter clock */
 172         ret = regmap_update_bits(periph_regs, PERIP_TIMER_CONTROL,
 173                                  0xf, 0x0);
 174         if (ret)
 175                 return ret;
 176
 177         sys_clk = of_clk_get_by_name(node, "sys");
 178         if (IS_ERR(sys_clk)) {
 179                 pr_err("clock get failed (%ld)\n", PTR_ERR(sys_clk));
 180                 return PTR_ERR(sys_clk);
 181         }
 182
 183         fast_clk = of_clk_get_by_name(node, "fast");
 184         if (IS_ERR(fast_clk)) {
 185                 pr_err("clock get failed (%lu)\n", PTR_ERR(fast_clk));
 186                 return PTR_ERR(fast_clk);
 187         }
 188
 189         ret = clk_prepare_enable(sys_clk);
 190         if (ret < 0) {
 191                 pr_err("failed to enable clock (%d)\n", ret);
 192                 return ret;
 193         }
 194
 195         ret = clk_prepare_enable(fast_clk);
 196         if (ret < 0) {
 197                 pr_err("failed to enable clock (%d)\n", ret);
 198                 clk_disable_unprepare(sys_clk);
 199                 return ret;
 200         }
 201
 202         rate = clk_get_rate(fast_clk);
 203
 204         /* Disable irq's for clocksource usage */
 205         gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 0);
 206         gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 1);
 207         gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 2);
 208         gpt_writel(pcs_gpt.base, 0, TIMER_IRQ_MASK, 3);
 209
 210         /* Enable timer block */
 211         writel(TIMER_ME_GLOBAL, pcs_gpt.base);
 212
 213         raw_spin_lock_init(&pcs_gpt.lock);
 214         sched_clock_register(pistachio_read_sched_clock, 32, rate);
 215         return clocksource_register_hz(&pcs_gpt.cs, rate);
 216 }
 217 TIMER_OF_DECLARE(pistachio_gptimer, "img,pistachio-gptimer",
 218                        pistachio_clksrc_of_init);