rp2040: Add initial support for the rp2040 mcu

Support the rp2040 (as tested on a Raspberry Pi Pico board).  This
adds basic uart, timer, gpio, and watchdog support.

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

1 files changed, 70 insertions, 0 deletions

diff --git a/src/rp2040/timer.c b/src/rp2040/timer.c
new file mode 100644
index 00000000..5401933e
--- /dev/null
+++ b/src/rp2040/timer.c
@@ -0,0 +1,70 @@
+// rp2040 timer support
+//
+// Copyright (C) 2021  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/irq.h" // irq_disable
+#include "board/misc.h" // timer_read_time
+#include "board/timer_irq.h" // timer_dispatch_many
+#include "command.h" // DECL_SHUTDOWN
+#include "hardware/structs/resets.h" // RESETS_RESET_UART0_BITS
+#include "hardware/structs/timer.h" // RESETS_RESET_UART0_BITS
+#include "internal.h" // enable_pclock
+#include "sched.h" // DECL_INIT
+
+
+/****************************************************************
+ * Low level timer code
+ ****************************************************************/
+
+// Return the current time (in absolute clock ticks).
+uint32_t
+timer_read_time(void)
+{
+    return timer_hw->timerawl;
+}
+
+static inline void
+timer_set(uint32_t next)
+{
+    timer_hw->alarm[0] = next;
+}
+
+// Activate timer dispatch as soon as possible
+void
+timer_kick(void)
+{
+    timer_set(timer_read_time() + 50);
+}
+
+
+/****************************************************************
+ * Setup and irqs
+ ****************************************************************/
+
+// Hardware timer IRQ handler - dispatch software timers
+void __aligned(16)
+TIMER0_IRQHandler(void)
+{
+    irq_disable();
+    timer_hw->intr = 1;
+    uint32_t next = timer_dispatch_many();
+    timer_set(next);
+    irq_enable();
+}
+
+void
+timer_init(void)
+{
+    irq_disable();
+    enable_pclock(RESETS_RESET_TIMER_BITS);
+    timer_hw->timelw = 0;
+    timer_hw->timehw = 0;
+    armcm_enable_irq(TIMER0_IRQHandler, TIMER_IRQ_0_IRQn, 2);
+    timer_hw->inte = 1;
+    timer_kick();
+    irq_enable();
+}
+DECL_INIT(timer_init);