generic: Move generic parts of sam3x8e timer.c to generic directory

Most of sam3x8e/timer.c is going to be platform agnostic for any board
with standard irq handling.  Move the generic code into a new file
generic/timer.c.

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

src/avr/main.c

@@ -4,9 +4,13 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
+#include "autoconf.h" // CONFIG_MCU
+#include "command.h" // DECL_CONSTANT
 #include "irq.h" // irq_enable
 #include "sched.h" // sched_main
 
+DECL_CONSTANT(MCU, CONFIG_MCU);
+
 // Main entry point for avr code.
 int
 main(void)

src/avr/timer.c

@@ -17,7 +17,6 @@
  ****************************************************************/
 
 DECL_CONSTANT(CLOCK_FREQ, F_CPU);
-DECL_CONSTANT(MCU, CONFIG_MCU);
 
 // Return the number of clock ticks for a given number of microseconds
 uint32_t

src/generic/timer.c

@@ -0,0 +1,87 @@
+// Generic interrupt based timer helper functions
+//
+// Copyright (C) 2017  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "autoconf.h" // CONFIG_CLOCK_FREQ
+#include "board/irq.h" // irq_disable
+#include "board/misc.h" // timer_from_us
+#include "command.h" // shutdown
+#include "sched.h" // sched_timer_kick
+
+// In order to use this code the board must still define
+// timer_read_time().  In addition, it must also provide a timer_set()
+// function.
+void timer_set(uint32_t next);
+
+DECL_CONSTANT(CLOCK_FREQ, CONFIG_CLOCK_FREQ);
+
+// Return the number of clock ticks for a given number of microseconds
+uint32_t
+timer_from_us(uint32_t us)
+{
+    return us * (CONFIG_CLOCK_FREQ / 1000000);
+}
+
+// Called by main code once every millisecond.  (IRQs disabled.)
+void
+timer_periodic(void)
+{
+}
+
+static uint32_t timer_repeat_until;
+#define TIMER_IDLE_REPEAT_TICKS timer_from_us(500)
+#define TIMER_REPEAT_TICKS timer_from_us(100)
+
+#define TIMER_MIN_TRY_TICKS timer_from_us(1)
+#define TIMER_DEFER_REPEAT_TICKS timer_from_us(5)
+
+// Set the next timer wake time (in absolute clock ticks) or return 1
+// if the next timer is too close to schedule.  Caller must disable
+// irqs.
+uint8_t
+timer_try_set_next(uint32_t next)
+{
+    uint32_t now = timer_read_time();
+    int32_t diff = next - now;
+    if (diff > (int32_t)TIMER_MIN_TRY_TICKS)
+        // Schedule next timer normally.
+        goto done;
+
+    // Next timer is in the past or near future - can't reschedule to it
+    if (likely(sched_is_before(now, timer_repeat_until))) {
+        // Can run more timers from this irq; briefly allow irqs
+        irq_enable();
+        while (diff >= 0) {
+            // Next timer is in the near future - wait for time to occur
+            now = timer_read_time();
+            diff = next - now;
+        }
+        irq_disable();
+        return 0;
+    }
+    if (diff < (int32_t)(-timer_from_us(1000)))
+        goto fail;
+
+    // Too many repeat timers from a single interrupt - force a pause
+    timer_repeat_until = now + TIMER_REPEAT_TICKS;
+    next = now + TIMER_DEFER_REPEAT_TICKS;
+
+done:
+    timer_set(next);
+    return 1;
+fail:
+    shutdown("Rescheduled timer in the past");
+}
+
+// Periodic background task that temporarily boosts priority of
+// timers.  This helps prioritize timers when tasks are idling.
+static void
+timer_task(void)
+{
+    irq_disable();
+    timer_repeat_until = timer_read_time() + TIMER_IDLE_REPEAT_TICKS;
+    irq_enable();
+}
+DECL_TASK(timer_task);

src/sam3x8e/Makefile

@@ -16,7 +16,7 @@ LDFLAGS-y += --specs=nano.specs --specs=nosys.specs
 
 # Add source files
 src-y += sam3x8e/main.c sam3x8e/timer.c sam3x8e/gpio.c
-src-y += generic/crc16_ccitt.c generic/armcm_irq.c
+src-y += generic/crc16_ccitt.c generic/armcm_irq.c generic/timer.c
 src-y += ../lib/cmsis-sam3x8e/source/system_sam3xa.c
 src-y += ../lib/cmsis-sam3x8e/source/gcc/startup_sam3xa.c
 src-$(CONFIG_SERIAL) += sam3x8e/serial.c

src/sam3x8e/main.c

@@ -5,9 +5,12 @@
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
 #include "board/misc.h" // alloc_maxsize
+#include "command.h" // DECL_CONSTANT
 #include "sam3x8e.h" // WDT
 #include "sched.h" // sched_main
 
+DECL_CONSTANT(MCU, "sam3x8e");
+
 
 /****************************************************************
  * watchdog handler

src/sam3x8e/timer.c

@@ -4,28 +4,12 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
-#include "autoconf.h" // CONFIG_CLOCK_FREQ
 #include "board/irq.h" // irq_disable
-#include "board/misc.h" // timer_from_us
+#include "board/misc.h" // timer_read_time
-#include "command.h" // shutdown
+#include "command.h" // DECL_SHUTDOWN
 #include "sam3x8e.h" // TC0
 #include "sched.h" // sched_timer_kick
 
-
-/****************************************************************
- * Low level timer code
- ****************************************************************/
-
-DECL_CONSTANT(CLOCK_FREQ, CONFIG_CLOCK_FREQ);
-DECL_CONSTANT(MCU, "sam3x8e");
-
-// Return the number of clock ticks for a given number of microseconds
-uint32_t
-timer_from_us(uint32_t us)
-{
-    return us * (CONFIG_CLOCK_FREQ / 1000000);
-}
-
 // IRQ handler
 void __visible
 TC0_Handler(void)
@@ -37,12 +21,20 @@ TC0_Handler(void)
     irq_enable();
 }
 
-static void
+// Set the next irq time
+void
 timer_set(uint32_t value)
 {
     TC0->TC_CHANNEL[0].TC_RA = value;
 }
 
+// Return the current time (in absolute clock ticks).
+uint32_t
+timer_read_time(void)
+{
+    return TC0->TC_CHANNEL[0].TC_CV;
+}
+
 static void
 timer_init(void)
 {
@@ -70,72 +62,3 @@ timer_shutdown(void)
     TC0->TC_CHANNEL[0].TC_SR; // read to clear irq pending
 }
 DECL_SHUTDOWN(timer_shutdown);
-
-// Called by main code once every millisecond.  (IRQs disabled.)
-void
-timer_periodic(void)
-{
-}
-
-// Return the current time (in absolute clock ticks).
-uint32_t
-timer_read_time(void)
-{
-    return TC0->TC_CHANNEL[0].TC_CV;
-}
-
-static uint32_t timer_repeat_until;
-#define TIMER_IDLE_REPEAT_TICKS timer_from_us(500)
-#define TIMER_REPEAT_TICKS timer_from_us(100)
-
-#define TIMER_MIN_TRY_TICKS timer_from_us(1)
-#define TIMER_DEFER_REPEAT_TICKS timer_from_us(5)
-
-// Set the next timer wake time (in absolute clock ticks) or return 1
-// if the next timer is too close to schedule.  Caller must disable
-// irqs.
-uint8_t
-timer_try_set_next(uint32_t next)
-{
-    uint32_t now = timer_read_time();
-    int32_t diff = next - now;
-    if (diff > (int32_t)TIMER_MIN_TRY_TICKS)
-        // Schedule next timer normally.
-        goto done;
-
-    // Next timer is in the past or near future - can't reschedule to it
-    if (likely(sched_is_before(now, timer_repeat_until))) {
-        // Can run more timers from this irq; briefly allow irqs
-        irq_enable();
-        while (diff >= 0) {
-            // Next timer is in the near future - wait for time to occur
-            now = timer_read_time();
-            diff = next - now;
-        }
-        irq_disable();
-        return 0;
-    }
-    if (diff < (int32_t)(-timer_from_us(1000)))
-        goto fail;
-
-    // Too many repeat timers from a single interrupt - force a pause
-    timer_repeat_until = now + TIMER_REPEAT_TICKS;
-    next = now + TIMER_DEFER_REPEAT_TICKS;
-
-done:
-    timer_set(next);
-    return 1;
-fail:
-    shutdown("Rescheduled timer in the past");
-}
-
-// Periodic background task that temporarily boosts priority of
-// timers.  This helps prioritize timers when tasks are idling.
-static void
-timer_task(void)
-{
-    irq_disable();
-    timer_repeat_until = timer_read_time() + TIMER_IDLE_REPEAT_TICKS;
-    irq_enable();
-}
-DECL_TASK(timer_task);