1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) Maxime Coquelin 2015 4 * Author: Maxime Coquelin <mcoquelin.stm32@gmail.com> 5 * 6 * Inspired by time-efm32.c from Uwe Kleine-Koenig 7 */ 8 9 #include <linux/kernel.h> 10 #include <linux/clocksource.h> 11 #include <linux/clockchips.h> 12 #include <linux/delay.h> 13 #include <linux/irq.h> 14 #include <linux/interrupt.h> 15 #include <linux/of.h> 16 #include <linux/of_address.h> 17 #include <linux/of_irq.h> 18 #include <linux/clk.h> 19 #include <linux/reset.h> 20 #include <linux/sched_clock.h> 21 #include <linux/slab.h> 22 23 #include "timer-of.h" 24 25 #define TIM_CR1 0x00 26 #define TIM_DIER 0x0c 27 #define TIM_SR 0x10 28 #define TIM_EGR 0x14 29 #define TIM_CNT 0x24 30 #define TIM_PSC 0x28 31 #define TIM_ARR 0x2c 32 #define TIM_CCR1 0x34 33 34 #define TIM_CR1_CEN BIT(0) 35 #define TIM_CR1_UDIS BIT(1) 36 #define TIM_CR1_OPM BIT(3) 37 #define TIM_CR1_ARPE BIT(7) 38 39 #define TIM_DIER_UIE BIT(0) 40 #define TIM_DIER_CC1IE BIT(1) 41 42 #define TIM_SR_UIF BIT(0) 43 44 #define TIM_EGR_UG BIT(0) 45 46 #define TIM_PSC_MAX USHRT_MAX 47 #define TIM_PSC_CLKRATE 10000 48 49 struct stm32_timer_private { 50 int bits; 51 }; 52 53 /** 54 * stm32_timer_of_bits_set - set accessor helper 55 * @to: a timer_of structure pointer 56 * @bits: the number of bits (16 or 32) 57 * 58 * Accessor helper to set the number of bits in the timer-of private 59 * structure. 60 * 61 */ 62 static void stm32_timer_of_bits_set(struct timer_of *to, int bits) 63 { 64 struct stm32_timer_private *pd = to->private_data; 65 66 pd->bits = bits; 67 } 68 69 /** 70 * stm32_timer_of_bits_get - get accessor helper 71 * @to: a timer_of structure pointer 72 * 73 * Accessor helper to get the number of bits in the timer-of private 74 * structure. 75 * 76 * Returns: an integer corresponding to the number of bits. 77 */ 78 static int stm32_timer_of_bits_get(struct timer_of *to) 79 { 80 struct stm32_timer_private *pd = to->private_data; 81 82 return pd->bits; 83 } 84 85 static void __iomem *stm32_timer_cnt __read_mostly; 86 87 static u64 notrace stm32_read_sched_clock(void) 88 { 89 return readl_relaxed(stm32_timer_cnt); 90 } 91 92 static struct delay_timer stm32_timer_delay; 93 94 static unsigned long stm32_read_delay(void) 95 { 96 return readl_relaxed(stm32_timer_cnt); 97 } 98 99 static void stm32_clock_event_disable(struct timer_of *to) 100 { 101 writel_relaxed(0, timer_of_base(to) + TIM_DIER); 102 } 103 104 /** 105 * stm32_timer_start - Start the counter without event 106 * @to: a timer_of structure pointer 107 * 108 * Start the timer in order to have the counter reset and start 109 * incrementing but disable interrupt event when there is a counter 110 * overflow. By default, the counter direction is used as upcounter. 111 */ 112 static void stm32_timer_start(struct timer_of *to) 113 { 114 writel_relaxed(TIM_CR1_UDIS | TIM_CR1_CEN, timer_of_base(to) + TIM_CR1); 115 } 116 117 static int stm32_clock_event_shutdown(struct clock_event_device *clkevt) 118 { 119 struct timer_of *to = to_timer_of(clkevt); 120 121 stm32_clock_event_disable(to); 122 123 return 0; 124 } 125 126 static int stm32_clock_event_set_next_event(unsigned long evt, 127 struct clock_event_device *clkevt) 128 { 129 struct timer_of *to = to_timer_of(clkevt); 130 unsigned long now, next; 131 132 next = readl_relaxed(timer_of_base(to) + TIM_CNT) + evt; 133 writel_relaxed(next, timer_of_base(to) + TIM_CCR1); 134 now = readl_relaxed(timer_of_base(to) + TIM_CNT); 135 136 if ((next - now) > evt) 137 return -ETIME; 138 139 writel_relaxed(TIM_DIER_CC1IE, timer_of_base(to) + TIM_DIER); 140 141 return 0; 142 } 143 144 static int stm32_clock_event_set_periodic(struct clock_event_device *clkevt) 145 { 146 struct timer_of *to = to_timer_of(clkevt); 147 148 stm32_timer_start(to); 149 150 return stm32_clock_event_set_next_event(timer_of_period(to), clkevt); 151 } 152 153 static int stm32_clock_event_set_oneshot(struct clock_event_device *clkevt) 154 { 155 struct timer_of *to = to_timer_of(clkevt); 156 157 stm32_timer_start(to); 158 159 return 0; 160 } 161 162 static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id) 163 { 164 struct clock_event_device *clkevt = (struct clock_event_device *)dev_id; 165 struct timer_of *to = to_timer_of(clkevt); 166 167 writel_relaxed(0, timer_of_base(to) + TIM_SR); 168 169 if (clockevent_state_periodic(clkevt)) 170 stm32_clock_event_set_periodic(clkevt); 171 else 172 stm32_clock_event_shutdown(clkevt); 173 174 clkevt->event_handler(clkevt); 175 176 return IRQ_HANDLED; 177 } 178 179 /** 180 * stm32_timer_set_width - Sort out the timer width (32/16) 181 * @to: a pointer to a timer-of structure 182 * 183 * Write the 32-bit max value and read/return the result. If the timer 184 * is 32 bits wide, the result will be UINT_MAX, otherwise it will 185 * be truncated by the 16-bit register to USHRT_MAX. 186 * 187 */ 188 static void __init stm32_timer_set_width(struct timer_of *to) 189 { 190 u32 width; 191 192 writel_relaxed(UINT_MAX, timer_of_base(to) + TIM_ARR); 193 194 width = readl_relaxed(timer_of_base(to) + TIM_ARR); 195 196 stm32_timer_of_bits_set(to, width == UINT_MAX ? 32 : 16); 197 } 198 199 /** 200 * stm32_timer_set_prescaler - Compute and set the prescaler register 201 * @to: a pointer to a timer-of structure 202 * 203 * Depending on the timer width, compute the prescaler to always 204 * target a 10MHz timer rate for 16 bits. 32-bit timers are 205 * considered precise and long enough to not use the prescaler. 206 */ 207 static void __init stm32_timer_set_prescaler(struct timer_of *to) 208 { 209 int prescaler = 1; 210 211 if (stm32_timer_of_bits_get(to) != 32) { 212 prescaler = DIV_ROUND_CLOSEST(timer_of_rate(to), 213 TIM_PSC_CLKRATE); 214 /* 215 * The prescaler register is an u16, the variable 216 * can't be greater than TIM_PSC_MAX, let's cap it in 217 * this case. 218 */ 219 prescaler = prescaler < TIM_PSC_MAX ? prescaler : TIM_PSC_MAX; 220 } 221 222 writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC); 223 writel_relaxed(TIM_EGR_UG, timer_of_base(to) + TIM_EGR); 224 writel_relaxed(0, timer_of_base(to) + TIM_SR); 225 226 /* Adjust rate and period given the prescaler value */ 227 to->of_clk.rate = DIV_ROUND_CLOSEST(to->of_clk.rate, prescaler); 228 to->of_clk.period = DIV_ROUND_UP(to->of_clk.rate, HZ); 229 } 230 231 static int __init stm32_clocksource_init(struct timer_of *to) 232 { 233 u32 bits = stm32_timer_of_bits_get(to); 234 const char *name = to->np->full_name; 235 236 /* 237 * This driver allows to register several timers and relies on 238 * the generic time framework to select the right one. 239 * However, nothing allows to do the same for the 240 * sched_clock. We are not interested in a sched_clock for the 241 * 16-bit timers but only for the 32-bit one, so if no 32-bit 242 * timer is registered yet, we select this 32-bit timer as a 243 * sched_clock. 244 */ 245 if (bits == 32 && !stm32_timer_cnt) { 246 247 /* 248 * Start immediately the counter as we will be using 249 * it right after. 250 */ 251 stm32_timer_start(to); 252 253 stm32_timer_cnt = timer_of_base(to) + TIM_CNT; 254 sched_clock_register(stm32_read_sched_clock, bits, timer_of_rate(to)); 255 pr_info("%s: STM32 sched_clock registered\n", name); 256 257 stm32_timer_delay.read_current_timer = stm32_read_delay; 258 stm32_timer_delay.freq = timer_of_rate(to); 259 register_current_timer_delay(&stm32_timer_delay); 260 pr_info("%s: STM32 delay timer registered\n", name); 261 } 262 263 return clocksource_mmio_init(timer_of_base(to) + TIM_CNT, name, 264 timer_of_rate(to), bits == 32 ? 250 : 100, 265 bits, clocksource_mmio_readl_up); 266 } 267 268 static void __init stm32_clockevent_init(struct timer_of *to) 269 { 270 u32 bits = stm32_timer_of_bits_get(to); 271 272 to->clkevt.name = to->np->full_name; 273 to->clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT; 274 to->clkevt.set_state_shutdown = stm32_clock_event_shutdown; 275 to->clkevt.set_state_periodic = stm32_clock_event_set_periodic; 276 to->clkevt.set_state_oneshot = stm32_clock_event_set_oneshot; 277 to->clkevt.tick_resume = stm32_clock_event_shutdown; 278 to->clkevt.set_next_event = stm32_clock_event_set_next_event; 279 to->clkevt.rating = bits == 32 ? 250 : 100; 280 281 clockevents_config_and_register(&to->clkevt, timer_of_rate(to), 0x1, 282 (1 << bits) - 1); 283 284 pr_info("%pOF: STM32 clockevent driver initialized (%d bits)\n", 285 to->np, bits); 286 } 287 288 static int __init stm32_timer_init(struct device_node *node) 289 { 290 struct reset_control *rstc; 291 struct timer_of *to; 292 int ret; 293 294 to = kzalloc(sizeof(*to), GFP_KERNEL); 295 if (!to) 296 return -ENOMEM; 297 298 to->flags = TIMER_OF_IRQ | TIMER_OF_CLOCK | TIMER_OF_BASE; 299 to->of_irq.handler = stm32_clock_event_handler; 300 301 ret = timer_of_init(node, to); 302 if (ret) 303 goto err; 304 305 to->private_data = kzalloc(sizeof(struct stm32_timer_private), 306 GFP_KERNEL); 307 if (!to->private_data) { 308 ret = -ENOMEM; 309 goto deinit; 310 } 311 312 rstc = of_reset_control_get(node, NULL); 313 if (!IS_ERR(rstc)) { 314 reset_control_assert(rstc); 315 reset_control_deassert(rstc); 316 } 317 318 stm32_timer_set_width(to); 319 320 stm32_timer_set_prescaler(to); 321 322 ret = stm32_clocksource_init(to); 323 if (ret) 324 goto deinit; 325 326 stm32_clockevent_init(to); 327 return 0; 328 329 deinit: 330 timer_of_cleanup(to); 331 err: 332 kfree(to); 333 return ret; 334 } 335 336 TIMER_OF_DECLARE(stm32, "st,stm32-timer", stm32_timer_init); 337