pru: Initial support for the Beaglebone PRU

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

src/pru/Makefile

@@ -0,0 +1,27 @@
+# Additional PRU build rules
+
+# Setup the toolchain
+CROSS_PREFIX=pru-
+
+dirs-y += src/pru src/generic
+dirs-y += lib/pru_rpmsg
+
+CFLAGS += -Os -mmcu=am335x.pru0
+CFLAGS += -Ilib/pru_rpmsg/include -Ilib/pru_rpmsg/include/am335x
+
+CFLAGS_klipper.o := $(filter-out -mmcu=%, $(CFLAGS_klipper.o))
+CFLAGS_klipper.elf := $(CFLAGS) -minrt -T src/pru/pru.lds
+CFLAGS_pru1.elf := $(filter-out -mmcu=%, $(CFLAGS)) -mmcu=am335x.pru1
+
+# Add source files
+src-y := $(filter-out debugcmds.c, $(src-y))
+src-y += pru/main.c pru/console.c pru/gpio.c
+src-y += generic/crc16_ccitt.c generic/timer_irq.c
+src-y += ../lib/pru_rpmsg/pru_rpmsg.c ../lib/pru_rpmsg/pru_virtqueue.c
+
+# Build the additional PRU1 binary
+target-y += $(OUT)pru1.elf
+
+$(OUT)pru1.elf: $(OUT)src/pru/pru1.o
+	@echo "  Linking $@"
+	$(Q)$(CC) $(CFLAGS_pru1.elf) $^ -o $@