stm32: Initial support for stm32f070

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/stm32/stm32f0_timer.c

@@ -0,0 +1,124 @@
+// STM32F0 timer support
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "board/armcm_boot.h" // armcm_enable_irq
+#include "board/armcm_timer.h" // udelay
+#include "board/internal.h" // TIM3
+#include "board/io.h" // readl
+#include "board/irq.h" // irq_disable
+#include "board/misc.h" // timer_read_time
+#include "sched.h" // DECL_INIT
+#include "command.h" // DECL_SHUTDOWN
+#include "board/timer_irq.h" // timer_dispatch_many
+
+
+/****************************************************************
+ * Low level timer code
+ ****************************************************************/
+
+// Use 32bit TIM2 timer if available (otherwise use 16bit TIM3 timer)
+#ifdef TIM2
+#define TIMx TIM2
+#define TIMx_IRQn TIM2_IRQn
+#define HAVE_TIMER_32BIT 1
+#else
+#define TIMx TIM3
+#define TIMx_IRQn TIM3_IRQn
+#define HAVE_TIMER_32BIT 0
+#endif
+
+static inline uint32_t
+timer_get(void)
+{
+    return TIMx->CNT;
+}
+
+static inline void
+timer_set(uint32_t next)
+{
+    TIMx->CCR1 = next;
+    TIMx->SR = 0;
+}
+
+// Activate timer dispatch as soon as possible
+void
+timer_kick(void)
+{
+    timer_set(timer_get() + 50);
+}
+
+
+/****************************************************************
+ * 16bit hardware timer to 32bit conversion
+ ****************************************************************/
+
+// High bits of timer (top 17 bits)
+static uint32_t timer_high;
+
+// Return the current time (in absolute clock ticks).
+uint32_t __always_inline
+timer_read_time(void)
+{
+    if (HAVE_TIMER_32BIT)
+        return timer_get();
+    uint32_t th = readl(&timer_high);
+    uint32_t cur = timer_get();
+    // Combine timer_high (high 17 bits) and current time (low 16
+    // bits) using method that handles rollovers correctly.
+    return (th ^ cur) + (th & 0xffff);
+}
+
+// Update timer_high every 0x8000 clock ticks
+static uint_fast8_t
+timer_event(struct timer *t)
+{
+    timer_high += 0x8000;
+    t->waketime = timer_high + 0x8000;
+    return SF_RESCHEDULE;
+}
+static struct timer wrap_timer = {
+    .func = timer_event,
+    .waketime = 0x8000,
+};
+
+void
+timer_reset(void)
+{
+    if (!HAVE_TIMER_32BIT)
+        sched_add_timer(&wrap_timer);
+}
+DECL_SHUTDOWN(timer_reset);
+
+
+/****************************************************************
+ * Setup and irqs
+ ****************************************************************/
+
+// Hardware timer IRQ handler - dispatch software timers
+void __aligned(16)
+TIMx_IRQHandler(void)
+{
+    irq_disable();
+    uint32_t next = timer_dispatch_many();
+    timer_set(next);
+    irq_enable();
+}
+
+void
+timer_init(void)
+{
+    irqstatus_t flag = irq_save();
+    enable_pclock((uint32_t)TIMx);
+    TIMx->CNT = 0;
+    TIMx->DIER = TIM_DIER_CC1IE;
+    TIMx->CCER = TIM_CCER_CC1E;
+    armcm_enable_irq(TIMx_IRQHandler, TIMx_IRQn, 2);
+    timer_kick();
+    timer_reset();
+    TIMx->CR1 = TIM_CR1_CEN;
+    irq_restore(flag);
+}
+DECL_INIT(timer_init);