pru: Initial support for the Beaglebone PRU

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

src/pru/main.c

@@ -0,0 +1,150 @@
+// Main starting point for PRU code.
+//
+// Copyright (C) 2017  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdint.h> // uint32_t
+#include <string.h> // memset
+#include <pru/io.h> // read_r31
+#include <pru_cfg.h> // CT_CFG
+#include <pru_iep.h> // CT_IEP
+#include <pru_intc.h> // CT_INTC
+#include "autoconf.h" // CONFIG_CLOCK_FREQ
+#include "board/misc.h" // timer_from_us
+#include "board/irq.h" // irq_disable
+#include "command.h" // shutdown
+#include "generic/timer_irq.h" // timer_dispatch_many
+#include "internal.h" // IEP_IRQ
+#include "sched.h" // sched_main
+
+DECL_CONSTANT(MCU, "pru");
+
+
+/****************************************************************
+ * Timers
+ ****************************************************************/
+
+void
+irq_disable(void)
+{
+}
+
+void
+irq_enable(void)
+{
+}
+
+irqstatus_t
+irq_save(void)
+{
+    return 0;
+}
+
+void
+irq_restore(irqstatus_t flag)
+{
+}
+
+static void
+timer_set(uint32_t value)
+{
+    CT_IEP.TMR_CMP0 = value;
+    CT_INTC.SECR0 = 1 << IEP_EVENT;
+}
+
+uint32_t
+timer_read_time(void)
+{
+    return CT_IEP.TMR_CNT;
+}
+
+static void
+_irq_poll(void)
+{
+    CT_IEP.TMR_CMP_STS = 0xff;
+    uint32_t next = timer_dispatch_many();
+    timer_set(next);
+}
+void
+irq_poll(void)
+{
+    if (read_r31() & (1 << (IEP_IRQ + R31_IRQ_OFFSET)))
+        _irq_poll();
+}
+
+static void
+timer_shutdown(void)
+{
+    // Reenable timer irq
+    timer_set(timer_read_time() + 50);
+    CT_IEP.TMR_CMP_STS = 0xff;
+    __delay_cycles(4);
+    CT_INTC.SECR0 = 1 << IEP_EVENT;
+}
+DECL_SHUTDOWN(timer_shutdown);
+
+static void
+timer_init(void)
+{
+    timer_set(0);
+    CT_IEP.TMR_CMP_CFG = 0x01 << 1;
+    CT_IEP.TMR_GLB_CFG = 0x11;
+    timer_shutdown();
+}
+
+
+/****************************************************************
+ * Allocator
+ ****************************************************************/
+
+extern char _heap_start;
+static void *heap_ptr = &_heap_start;
+
+#define STACK_SIZE 256
+#define END_MEM ((void*)(8*1024 - STACK_SIZE))
+
+// Allocate an area of memory
+void *
+alloc_chunk(size_t size)
+{
+    if (heap_ptr + size > END_MEM)
+        shutdown("alloc_chunk failed");
+    void *data = heap_ptr;
+    heap_ptr += size;
+    memset(data, 0, size);
+    return data;
+}
+
+// Allocate an array of chunks
+void *
+alloc_chunks(size_t size, size_t count, size_t *avail)
+{
+    size_t can_alloc = 0;
+    void *p = heap_ptr;
+    for (; can_alloc <= count && p + size <= END_MEM; can_alloc++, p += size)
+        ;
+    if (!can_alloc)
+        shutdown("alloc_chunks failed");
+    *avail = can_alloc;
+    return alloc_chunk(size * can_alloc);
+}
+
+
+/****************************************************************
+ * Startup
+ ****************************************************************/
+
+// Main entry point
+int
+main(void)
+{
+    // allow access to external memory
+    CT_CFG.SYSCFG_bit.STANDBY_INIT = 0;
+
+    console_init();
+    timer_init();
+
+    sched_main();
+    return 0;
+}