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   1 /*
   2  * Copyright © 2013 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_tim6.cr1 = ((0 << STM_TIM67_CR1_ARPE) |
  29                         (0 << STM_TIM67_CR1_OPM) |
  30                         (1 << STM_TIM67_CR1_URS) |
  31                         (0 << STM_TIM67_CR1_UDIS) |
  32                         (1 << STM_TIM67_CR1_CEN));
  33 }
  34
  35 static void
  36 ao_fast_timer_disable(void)
  37 {
  38         stm_tim6.cr1 = ((0 << STM_TIM67_CR1_ARPE) |
  39                         (0 << STM_TIM67_CR1_OPM) |
  40                         (1 << STM_TIM67_CR1_URS) |
  41                         (0 << STM_TIM67_CR1_UDIS) |
  42                         (0 << STM_TIM67_CR1_CEN));
  43 }
  44
  45 void
  46 ao_fast_timer_on(void (*callback)(void))
  47 {
  48         ao_fast_timer_callback[ao_fast_timer_count] = callback;
  49         if (!ao_fast_timer_count++)
  50                 ao_fast_timer_enable();
  51 }
  52
  53 void
  54 ao_fast_timer_off(void (*callback)(void))
  55 {
  56         uint8_t n;
  57
  58         for (n = 0; n < ao_fast_timer_count; n++)
  59                 if (ao_fast_timer_callback[n] == callback) {
  60                         for (; n < ao_fast_timer_count-1; n++) {
  61                                 ao_fast_timer_callback[n] = ao_fast_timer_callback[n+1];
  62                         }
  63                         if (!--ao_fast_timer_count)
  64                                 ao_fast_timer_disable();
  65                         break;
  66                 }
  67 }
  68
  69 void stm_tim6_isr(void)
  70 {
  71         uint8_t i;
  72         if (stm_tim6.sr & (1 << STM_TIM67_SR_UIF)) {
  73                 stm_tim6.sr = 0;
  74
  75                 for (i = 0; i < ao_fast_timer_count; i++)
  76                         (*ao_fast_timer_callback[i])();
  77         }
  78 }
  79
  80 /*
  81  * According to the STM clock-configuration, timers run
  82  * twice as fast as the APB1 clock *if* the APB1 prescaler
  83  * is greater than 1.
  84  */
  85
  86 #if AO_APB1_PRESCALER > 1
  87 #define TIMER_23467_SCALER 2
  88 #else
  89 #define TIMER_23467_SCALER 1
  90 #endif
  91
  92 #ifndef FAST_TIMER_FREQ
  93 #define FAST_TIMER_FREQ 10000
  94 #endif
  95
  96 #define TIMER_FAST      ((AO_PCLK1 * TIMER_23467_SCALER) / FAST_TIMER_FREQ)
  97
  98 void
  99 ao_fast_timer_init(void)
 100 {
 101         if (!ao_fast_timer_users) {
 102                 stm_nvic_set_enable(STM_ISR_TIM6_POS);
 103                 stm_nvic_set_priority(STM_ISR_TIM6_POS, AO_STM_NVIC_CLOCK_PRIORITY);
 104
 105                 /* Turn on timer 6 */
 106                 stm_rcc.apb1enr |= (1 << STM_RCC_APB1ENR_TIM6EN);
 107
 108                 stm_tim6.psc = TIMER_FAST;
 109                 stm_tim6.arr = 9;
 110                 stm_tim6.cnt = 0;
 111
 112                 /* Enable update interrupt */
 113                 stm_tim6.dier = (1 << STM_TIM67_DIER_UIE);
 114
 115                 /* Poke timer to reload values */
 116                 stm_tim6.egr |= (1 << STM_TIM67_EGR_UG);
 117
 118                 stm_tim6.cr2 = (STM_TIM67_CR2_MMS_RESET << STM_TIM67_CR2_MMS);
 119                 ao_fast_timer_disable();
 120         }
 121         if (ao_fast_timer_users == AO_FAST_TIMER_MAX)
 122                 ao_panic(AO_PANIC_FAST_TIMER);
 123         ao_fast_timer_users++;
 124 }
 125