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   1 /*
   2  * Copyright © 2024 Keith Packard <keithp@keithp.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  17  */
  18 #include <ao.h>
  19 #include <ao_fast_timer.h>
  20
  21 static void (*ao_fast_timer_callback[AO_FAST_TIMER_MAX])(void);
  22 static uint8_t ao_fast_timer_count;
  23 static uint8_t ao_fast_timer_users;
  24
  25 static void
  26 ao_fast_timer_enable(void)
  27 {
  28         stm_tim1.cr1 = ((0 << STM_TIM18_CR1_CKD) |
  29                         (0 << STM_TIM18_CR1_ARPE) |
  30                         (0 << STM_TIM18_CR1_CMS) |
  31                         (0 << STM_TIM18_CR1_DIR) |
  32                         (0 << STM_TIM18_CR1_OPM) |
  33                         (1 << STM_TIM18_CR1_URS) |
  34                         (0 << STM_TIM18_CR1_UDIS) |
  35                         (1 << STM_TIM18_CR1_CEN));
  36 }
  37
  38 static void
  39 ao_fast_timer_disable(void)
  40 {
  41         stm_tim1.cr1 = ((0 << STM_TIM18_CR1_CKD) |
  42                         (0 << STM_TIM18_CR1_ARPE) |
  43                         (0 << STM_TIM18_CR1_CMS) |
  44                         (0 << STM_TIM18_CR1_DIR) |
  45                         (0 << STM_TIM18_CR1_OPM) |
  46                         (1 << STM_TIM18_CR1_URS) |
  47                         (0 << STM_TIM18_CR1_UDIS) |
  48                         (0 << STM_TIM18_CR1_CEN));
  49 }
  50
  51 void
  52 ao_fast_timer_on(void (*callback)(void))
  53 {
  54         ao_fast_timer_callback[ao_fast_timer_count] = callback;
  55         if (!ao_fast_timer_count++)
  56                 ao_fast_timer_enable();
  57 }
  58
  59 void
  60 ao_fast_timer_off(void (*callback)(void))
  61 {
  62         uint8_t n;
  63
  64         for (n = 0; n < ao_fast_timer_count; n++)
  65                 if (ao_fast_timer_callback[n] == callback) {
  66                         for (; n < ao_fast_timer_count-1; n++) {
  67                                 ao_fast_timer_callback[n] = ao_fast_timer_callback[n+1];
  68                         }
  69                         if (!--ao_fast_timer_count)
  70                                 ao_fast_timer_disable();
  71                         break;
  72                 }
  73 }
  74
  75 void stm_tim1_up_isr(void)
  76 {
  77         uint8_t i;
  78         if (stm_tim1.sr & (1 << STM_TIM18_SR_UIF)) {
  79                 stm_tim1.sr = 0;
  80
  81                 for (i = 0; i < ao_fast_timer_count; i++)
  82                         (*ao_fast_timer_callback[i])();
  83         }
  84 }
  85
  86 /*
  87  * According to the STM clock-configuration, timers run
  88  * twice as fast as the APB2 clock *if* the APB2 prescaler
  89  * is greater than 1.
  90  */
  91
  92 #if AO_APB1_PRESCALER > 1
  93 #define TIMER_18_SCALER 2
  94 #else
  95 #define TIMER_18_SCALER 1
  96 #endif
  97
  98 #ifndef FAST_TIMER_FREQ
  99 #define FAST_TIMER_FREQ 10000
 100 #endif
 101
 102 #define TIMER_FAST      ((AO_PCLK2 * TIMER_18_SCALER) / FAST_TIMER_FREQ)
 103
 104 void
 105 ao_fast_timer_init(void)
 106 {
 107         if (!ao_fast_timer_users) {
 108                 stm_nvic_set_enable(STM_ISR_TIM1_UP_POS);
 109                 stm_nvic_set_priority(STM_ISR_TIM1_UP_POS, AO_STM_NVIC_CLOCK_PRIORITY);
 110
 111                 /* Turn on timer 1 */
 112                 stm_rcc.apb2enr |= (1 << STM_RCC_APB2ENR_TIM1EN);
 113
 114                 stm_tim1.psc = TIMER_FAST;
 115                 stm_tim1.arr = 9;
 116                 stm_tim1.cnt = 0;
 117
 118                 /* Enable update interrupt */
 119                 stm_tim1.dier = (1 << STM_TIM18_DIER_UIE);
 120
 121                 /* Poke timer to reload values */
 122                 stm_tim1.egr |= (1 << STM_TIM18_EGR_UG);
 123
 124                 stm_tim1.cr2 = (STM_TIM18_CR2_MMS_RESET << STM_TIM18_CR2_MMS);
 125                 ao_fast_timer_disable();
 126         }
 127         if (ao_fast_timer_users == AO_FAST_TIMER_MAX)
 128                 ao_panic(AO_PANIC_FAST_TIMER);
 129         ao_fast_timer_users++;
 130 }
 131