PoC: Add LED toggling interrupt example

Add example firmware for demoing interrupts on Tkey hardware.

hw/application_fpga/Makefile

@@ -148,6 +148,10 @@ IRQPOC_OBJS = \
 	$(P)/fw/irqpoc/main.o \
 	$(P)/fw/irqpoc/start.o
 
+IRQPOC_LED_TOGGLE_OBJS = \
+	$(P)/fw/irqpoc_led_toggle/main.o \
+	$(P)/fw/irqpoc_led_toggle/start.o
+
 #-------------------------------------------------------------------
 # All: Complete build of HW and FW.
 #-------------------------------------------------------------------
@@ -185,6 +189,7 @@ LDFLAGS = -T $(P)/fw/tk1/firmware.lds
 $(FIRMWARE_OBJS): $(FIRMWARE_DEPS)
 $(TESTFW_OBJS): $(FIRMWARE_DEPS)
 $(IRQPOC_OBJS): $(FIRMWARE_DEPS)
+$(IRQPOC_LED_TOGGLE_OBJS): $(FIRMWARE_DEPS)
 
 firmware.elf: $(FIRMWARE_OBJS) $(P)/fw/tk1/firmware.lds
 	$(CC) $(CFLAGS) $(FIRMWARE_OBJS) $(LDFLAGS) -o $@
@@ -230,6 +235,9 @@ testfw.elf: $(TESTFW_OBJS) $(P)/fw/tk1/firmware.lds
 irqpoc.elf: $(IRQPOC_OBJS) $(P)/fw/tk1/firmware.lds
 	$(CC) $(CFLAGS) $(IRQPOC_OBJS) $(LDFLAGS) -o $@
 
+irqpoc_led_toggle.elf: $(IRQPOC_LED_TOGGLE_OBJS) $(P)/fw/tk1/firmware.lds
+	$(CC) $(CFLAGS) $(IRQPOC_LED_TOGGLE_OBJS) $(LDFLAGS) -o $@
+
 # Generate a fake BRAM file that will be filled in later after place-n-route
 bram_fw.hex:
 	$(ICESTORM_PATH)icebram -v -g 32 $(BRAM_FW_SIZE) > $@
@@ -505,6 +513,7 @@ clean_fw:
 	rm -f testfw.{elf,elf.map,bin,hex}
 	rm -f $(TESTFW_OBJS)
 	rm -f $(IRQPOC_OBJS)
+	rm -f $(IRQPOC_LED_TOGGLE_OBJS)
 	rm -f qemu_firmware.elf
 .PHONY: clean_fw
 

hw/application_fpga/fw/irqpoc_led_toggle/Makefile

@@ -0,0 +1,9 @@
+# Uses ../.clang-format
+FMTFILES=main.c
+.PHONY: fmt
+fmt:
+	clang-format --dry-run --ferror-limit=0 $(FMTFILES)
+	clang-format --verbose -i $(FMTFILES)
+.PHONY: checkfmt
+checkfmt:
+	clang-format --dry-run --ferror-limit=0 --Werror $(FMTFILES)

hw/application_fpga/fw/irqpoc_led_toggle/custom_ops.S

@@ -0,0 +1,102 @@
+// This is free and unencumbered software released into the public domain.
+//
+// Anyone is free to copy, modify, publish, use, compile, sell, or
+// distribute this software, either in source code form or as a compiled
+// binary, for any purpose, commercial or non-commercial, and by any
+// means.
+
+#define regnum_q0   0
+#define regnum_q1   1
+#define regnum_q2   2
+#define regnum_q3   3
+
+#define regnum_x0   0
+#define regnum_x1   1
+#define regnum_x2   2
+#define regnum_x3   3
+#define regnum_x4   4
+#define regnum_x5   5
+#define regnum_x6   6
+#define regnum_x7   7
+#define regnum_x8   8
+#define regnum_x9   9
+#define regnum_x10 10
+#define regnum_x11 11
+#define regnum_x12 12
+#define regnum_x13 13
+#define regnum_x14 14
+#define regnum_x15 15
+#define regnum_x16 16
+#define regnum_x17 17
+#define regnum_x18 18
+#define regnum_x19 19
+#define regnum_x20 20
+#define regnum_x21 21
+#define regnum_x22 22
+#define regnum_x23 23
+#define regnum_x24 24
+#define regnum_x25 25
+#define regnum_x26 26
+#define regnum_x27 27
+#define regnum_x28 28
+#define regnum_x29 29
+#define regnum_x30 30
+#define regnum_x31 31
+
+#define regnum_zero 0
+#define regnum_ra   1
+#define regnum_sp   2
+#define regnum_gp   3
+#define regnum_tp   4
+#define regnum_t0   5
+#define regnum_t1   6
+#define regnum_t2   7
+#define regnum_s0   8
+#define regnum_s1   9
+#define regnum_a0  10
+#define regnum_a1  11
+#define regnum_a2  12
+#define regnum_a3  13
+#define regnum_a4  14
+#define regnum_a5  15
+#define regnum_a6  16
+#define regnum_a7  17
+#define regnum_s2  18
+#define regnum_s3  19
+#define regnum_s4  20
+#define regnum_s5  21
+#define regnum_s6  22
+#define regnum_s7  23
+#define regnum_s8  24
+#define regnum_s9  25
+#define regnum_s10 26
+#define regnum_s11 27
+#define regnum_t3  28
+#define regnum_t4  29
+#define regnum_t5  30
+#define regnum_t6  31
+
+// x8 is s0 and also fp
+#define regnum_fp   8
+
+#define r_type_insn(_f7, _rs2, _rs1, _f3, _rd, _opc) \
+.word (((_f7) << 25) | ((_rs2) << 20) | ((_rs1) << 15) | ((_f3) << 12) | ((_rd) << 7) | ((_opc) << 0))
+
+#define picorv32_getq_insn(_rd, _qs) \
+r_type_insn(0b0000000, 0, regnum_ ## _qs, 0b100, regnum_ ## _rd, 0b0001011)
+
+#define picorv32_setq_insn(_qd, _rs) \
+r_type_insn(0b0000001, 0, regnum_ ## _rs, 0b010, regnum_ ## _qd, 0b0001011)
+
+#define picorv32_retirq_insn() \
+r_type_insn(0b0000010, 0, 0, 0b000, 0, 0b0001011)
+
+#define picorv32_maskirq_insn(_rd, _rs) \
+r_type_insn(0b0000011, 0, regnum_ ## _rs, 0b110, regnum_ ## _rd, 0b0001011)
+
+#define picorv32_waitirq_insn(_rd) \
+r_type_insn(0b0000100, 0, 0, 0b100, regnum_ ## _rd, 0b0001011)
+
+#define picorv32_timer_insn(_rd, _rs) \
+r_type_insn(0b0000101, 0, regnum_ ## _rs, 0b110, regnum_ ## _rd, 0b0001011)
+

hw/application_fpga/fw/irqpoc_led_toggle/main.c

@@ -0,0 +1,10 @@
+/*
+ * Copyright (C) 2022, 2023 - Tillitis AB
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+int main(void)
+{
+	while (1) {
+	}
+}

hw/application_fpga/fw/irqpoc_led_toggle/start.S

@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2022, 2023 - Tillitis AB
+ * SPDX-License-Identifier: GPL-2.0-only
+*/
+
+// Triggers both interrupts, one after the other, in an endless loop. The
+// interrupt handler updates the LED color depending on which interrupt
+// was triggered.
+// The LED color will alterate between blue and green.
+//
+// | IRQ number | Color |
+// |------------|-------|
+// | 30         | Blue  |
+// | 31         | Green |
+// | Unexpected | Red   |
+//
+
+#include "custom_ops.S"  // PicoRV32 custom instructions
+
+	.section ".text.init"
+	.globl _start
+_start:
+	j init
+
+
+	.=0x10 // IRQ handler at fixed address 0x10
+irq_handler:
+	// PicoRV32 stores the IRQ bitmask in x4.
+	// If bit 31 is 1: IRQ31 was triggered.
+	// If bit 30 is 1: IRQ30 was triggered.
+irq30_check:
+	li t4, (1 << 30)
+	bne x4, t4, irq31_check
+	call led_blue
+	call delay
+	j irq_source_check_done
+irq31_check:
+	li t4, (1 << 31)
+	bne x4, t4, unexpected_irq
+	call led_green
+	call delay
+	j irq_source_check_done
+unexpected_irq:
+	call led_red
+	call delay
+irq_source_check_done:
+	picorv32_retirq_insn() // Return from interrupt
+
+
+init:
+	li t0, 0x3fffffff // IRQ31 & IRQ30 mask
+	picorv32_maskirq_insn(zero, t0) // Enable IRQs
+
+irq_trigger_loop:
+	li t0, 0xe1000000 // IRQ31 trigger address
+	sw zero, 0(t0) // Raise IRQ by writing to interrupt trigger address.
+	               // Writing any data triggers an interrupt.
+
+	li t0, 0xe0000000 // IRQ30 trigger address
+	sw zero, 0(t0) // Raise IRQ by writing to interrupt trigger address.
+	               // Writing any data triggers an interrupt.
+	j irq_trigger_loop
+
+led_red:
+	li t2, 0xff000024
+	li t3, (1 << 2)
+	sw t3, 0(t2)
+	ret
+
+led_green:
+	li t2, 0xff000024
+	li t3, (1 << 1)
+	sw t3, 0(t2)
+	ret
+
+led_blue:
+	li t2, 0xff000024
+	li t3, (1 << 0)
+	sw t3, 0(t2)
+	ret
+
+delay:
+	li t5, 0x100000
+delay_dec:
+	addi t5, t5, -1
+	bne t5, zero, delay_dec
+	ret
+
+	.align 4 // Padding to please makehex.py which requires even 4-byte file
+	         // sizes.
+