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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; version 2 of the License.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  16  */
  17 #include <ao.h>
  18 #include <ao_fast_timer.h>
  19
  20 static void (*ao_fast_timer_callback[AO_FAST_TIMER_MAX])(void);
  21 static uint8_t ao_fast_timer_count;
  22 static uint8_t ao_fast_timer_users;
  23
  24 static void
  25 ao_fast_timer_enable(void)
  26 {
  27         stm_tim6.cr1 = ((0 << STM_TIM67_CR1_ARPE) |
  28                         (0 << STM_TIM67_CR1_OPM) |
  29                         (1 << STM_TIM67_CR1_URS) |
  30                         (0 << STM_TIM67_CR1_UDIS) |
  31                         (1 << STM_TIM67_CR1_CEN));
  32 }
  33
  34 static void
  35 ao_fast_timer_disable(void)
  36 {
  37         stm_tim6.cr1 = ((0 << STM_TIM67_CR1_ARPE) |
  38                         (0 << STM_TIM67_CR1_OPM) |
  39                         (1 << STM_TIM67_CR1_URS) |
  40                         (0 << STM_TIM67_CR1_UDIS) |
  41                         (0 << STM_TIM67_CR1_CEN));
  42 }
  43
  44 void
  45 ao_fast_timer_on(void (*callback)(void))
  46 {
  47         ao_fast_timer_callback[ao_fast_timer_count] = callback;
  48         if (!ao_fast_timer_count++)
  49                 ao_fast_timer_enable();
  50 }
  51
  52 void
  53 ao_fast_timer_off(void (*callback)(void))
  54 {
  55         uint8_t n;
  56
  57         for (n = 0; n < ao_fast_timer_count; n++)
  58                 if (ao_fast_timer_callback[n] == callback) {
  59                         for (; n < ao_fast_timer_count-1; n++) {
  60                                 ao_fast_timer_callback[n] = ao_fast_timer_callback[n+1];
  61                         }
  62                         if (!--ao_fast_timer_count)
  63                                 ao_fast_timer_disable();
  64                         break;
  65                 }
  66 }
  67
  68 void stm_tim6_isr(void)
  69 {
  70         uint8_t i;
  71         if (stm_tim6.sr & (1 << STM_TIM67_SR_UIF)) {
  72                 stm_tim6.sr = 0;
  73
  74                 for (i = 0; i < ao_fast_timer_count; i++)
  75                         (*ao_fast_timer_callback[i])();
  76         }
  77 }
  78
  79 /*
  80  * According to the STM clock-configuration, timers run
  81  * twice as fast as the APB1 clock *if* the APB1 prescaler
  82  * is greater than 1.
  83  */
  84
  85 #if AO_APB1_PRESCALER > 1
  86 #define TIMER_23467_SCALER 2
  87 #else
  88 #define TIMER_23467_SCALER 1
  89 #endif
  90
  91 #define TIMER_10kHz     ((AO_PCLK1 * TIMER_23467_SCALER) / 10000)
  92
  93 void
  94 ao_fast_timer_init(void)
  95 {
  96         if (!ao_fast_timer_users) {
  97                 stm_nvic_set_enable(STM_ISR_TIM6_POS);
  98                 stm_nvic_set_priority(STM_ISR_TIM6_POS, AO_STM_NVIC_CLOCK_PRIORITY);
  99
 100                 /* Turn on timer 6 */
 101                 stm_rcc.apb1enr |= (1 << STM_RCC_APB1ENR_TIM6EN);
 102
 103                 stm_tim6.psc = TIMER_10kHz;
 104                 stm_tim6.arr = 9;
 105                 stm_tim6.cnt = 0;
 106
 107                 /* Enable update interrupt */
 108                 stm_tim6.dier = (1 << STM_TIM67_DIER_UIE);
 109
 110                 /* Poke timer to reload values */
 111                 stm_tim6.egr |= (1 << STM_TIM67_EGR_UG);
 112
 113                 stm_tim6.cr2 = (STM_TIM67_CR2_MMS_RESET << STM_TIM67_CR2_MMS);
 114                 ao_fast_timer_disable();
 115         }
 116         if (ao_fast_timer_users == AO_FAST_TIMER_MAX)
 117                 ao_panic(AO_PANIC_FAST_TIMER);
 118         ao_fast_timer_users++;
 119 }
 120