soc/cores/cpu: Add initial uRV CPU support (not yet working).

litex/soc/cores/cpu/urv/__init__.py

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+from litex.soc.cores.cpu.urv.core import uRV

litex/soc/cores/cpu/urv/boot-helper.S

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+	.section .text, "ax", @progbits
+	.global boot_helper
+boot_helper:
+	jr x13

litex/soc/cores/cpu/urv/core.py

@@ -0,0 +1,210 @@
+#
+# This file is part of LiteX.
+#
+# Copyright (c) 2024 Florent Kermarrec <florent@enjoy-digital.fr>
+# SPDX-License-Identifier: BSD-2-Clause
+
+import os
+
+from migen import *
+
+from litex.gen import *
+
+from litex.soc.interconnect import wishbone
+from litex.soc.cores.cpu import CPU, CPU_GCC_TRIPLE_RISCV32
+
+# Variants -----------------------------------------------------------------------------------------
+
+CPU_VARIANTS = {
+    "standard": "urv",
+}
+
+# GCC Flags ----------------------------------------------------------------------------------------
+
+GCC_FLAGS = {
+    #                       /------------ Base ISA
+    #                       |    /------- Hardware Multiply + Divide
+    #                       |    |/----- Atomics
+    #                       |    ||/---- Compressed ISA
+    #                       |    |||/--- Single-Precision Floating-Point
+    #                       |    ||||/-- Double-Precision Floating-Point
+    #                       i    macfd
+    "standard": "-march=rv32i2p0_m    -mabi=ilp32",
+}
+
+# uRV ------------------------------------------------------------------------------------------
+
+class uRV(CPU):
+    category             = "softcore"
+    family               = "riscv"
+    name                 = "urv"
+    human_name           = "urv"
+    variants             = CPU_VARIANTS
+    data_width           = 32
+    endianness           = "little"
+    gcc_triple           = CPU_GCC_TRIPLE_RISCV32
+    linker_output_format = "elf32-littleriscv"
+    nop                  = "nop"
+    io_regions           = {0x8000_0000: 0x8000_0000} # Origin, Length.
+
+    # GCC Flags.
+    @property
+    def gcc_flags(self):
+        flags =  GCC_FLAGS[self.variant]
+        flags += " -D__urv__ "
+        return flags
+
+    def __init__(self, platform, variant="standard"):
+        self.platform     = platform
+        self.variant      = variant
+        self.human_name   = f"uRV-{variant.upper()}"
+        self.reset        = Signal()
+        self.ibus         = ibus = wishbone.Interface(data_width=32, address_width=32, addressing="byte")
+        self.dbus         = dbus = wishbone.Interface(data_width=32, address_width=32, addressing="byte")
+        self.periph_buses = [ibus, dbus] # Peripheral buses (Connected to main SoC's bus).
+        self.memory_buses = []      # Memory buses (Connected directly to LiteDRAM).
+
+        # uRV Signals.
+        # ------------
+        im_addr  = Signal(32)
+        im_rd    = Signal(1)
+        im_data  = Signal(32)
+        im_valid = Signal(1)
+
+        dm_addr        = Signal(32)
+        dm_data_s      = Signal(32)
+        dm_data_l      = Signal(32)
+        dm_data_select = Signal(4)
+        dm_store       = Signal()
+        dm_load        = Signal()
+        dm_load_done   = Signal()
+        dm_store_done  = Signal()
+
+        rst_count = Signal(8, reset=16)
+        self.sync += If(rst_count != 0, rst_count.eq(rst_count - 1))
+
+        # uRV Instance.
+        # -------------
+        self.cpu_params = dict(
+            # Parameters.
+            p_g_timer_frequency       = 1000,
+            p_g_clock_frequency       = 100000000,
+            p_g_with_hw_div           = 1,
+            p_g_with_hw_mulh          = 1,
+            p_g_with_hw_mul           = 1,
+            p_g_with_hw_debug         = 0,
+            p_g_with_ecc              = 0,
+            p_g_with_compressed_insns = 0,
+
+            # Clk / Rst.
+            i_clk_i            =  ClockSignal("sys"),
+            i_rst_i            = ~(ResetSignal("sys") | self.reset | (rst_count != 0)),
+
+            # Instruction Mem Bus.
+            o_im_addr_o        = im_addr,
+            o_im_rd_o          = im_rd,
+            i_im_data_i        = im_data,
+            i_im_valid_i       = im_valid,
+
+            # Data Mem Bus.
+            o_dm_addr_o        = dm_addr,
+            o_dm_data_s_o      = dm_data_s,
+            i_dm_data_l_i      = dm_data_l,
+            o_dm_data_select_o = dm_data_select,
+
+            o_dm_store_o       = dm_store,
+            o_dm_load_o        = dm_load,
+            i_dm_load_done_i   = dm_load_done,
+            i_dm_store_done_i  = dm_store_done,
+        )
+
+        # uRV Instruction Bus.
+        # --------------------
+        self.i_fsm = i_fsm = FSM(reset_state="IDLE")
+        i_fsm.act("IDLE",
+            If(im_rd,
+                NextValue(im_valid, 0),
+                NextState("READ")
+            )
+        )
+        i_fsm.act("READ",
+            ibus.stb.eq(1),
+            ibus.cyc.eq(1),
+            ibus.we.eq(0),
+            ibus.adr.eq(im_addr),
+            ibus.sel.eq(0b1111),
+            If(ibus.ack,
+                NextValue(im_valid, 1),
+                NextValue(im_data, ibus.dat_r),
+                NextState("IDLE")
+            )
+        )
+
+        # uRV Data Bus.
+        # -------------
+        self.d_fsm = d_fsm = FSM(reset_state="IDLE")
+        d_fsm.act("IDLE",
+            If(dm_store,
+                NextState("WRITE")
+            ),
+            If(dm_load,
+                NextState("READ")
+            )
+        )
+        d_fsm.act("WRITE",
+            dbus.stb.eq(1),
+            dbus.cyc.eq(1),
+            dbus.we.eq(1),
+            dbus.adr.eq(dm_addr),
+            dbus.sel.eq(dm_data_select),
+            dbus.dat_w.eq(dm_data_s),
+            If(dbus.ack,
+                NextState("IDLE")
+            )
+        )
+        d_fsm.act("READ",
+            dbus.stb.eq(1),
+            dbus.cyc.eq(1),
+            dbus.we.eq(0),
+            dbus.adr.eq(dm_addr),
+            dbus.sel.eq(dm_data_select),
+            If(dbus.ack,
+                dm_load_done.eq(1),
+                dm_data_l.eq(dbus.dat_r),
+                NextState("IDLE")
+            )
+        )
+
+        # Add Verilog sources.
+        # --------------------
+        self.add_sources(platform, variant)
+
+    def set_reset_address(self, reset_address):
+        assert reset_address == 0
+        self.reset_address = reset_address
+
+    @staticmethod
+    def add_sources(platform, variant):
+        if not os.path.exists("urv-core"):
+            os.system(f"git clone https://ohwr.org/project/urv-core/")
+        vdir = "urv-core/rtl"
+        platform.add_verilog_include_path("urv-core/rtl")
+        platform.add_sources([
+            "urv-core/rtl/urv_cpu.v",
+            "urv-core/rtl/urv_exec.v",
+            "urv-core/rtl/urv_fetch.v",
+            "urv-core/rtl/urv_decode.v",
+            "urv-core/rtl/urv_regfile.v",
+            "urv-core/rtl/urv_writeback.v",
+            "urv-core/rtl/urv_shifter.v",
+            "urv-core/rtl/urv_multiply.v",
+            "urv-core/rtl/urv_divide.v",
+            "urv-core/rtl/urv_csr.v",
+            "urv-core/rtl/urv_timer.v",
+            "urv-core/rtl/urv_exceptions.v",
+            "urv-core/rtl/urv_iram.v",
+            "urv-core/rtl/urv_ecc.v",
+        ])
+
+    def do_finalize(self):
+        self.specials += Instance("urv_cpu", **self.cpu_params)

litex/soc/cores/cpu/urv/crt0.S

@@ -0,0 +1,75 @@
+#define MIE_MEIE 	0x800
+
+	.global _start
+_start:
+	j reset_vector
+
+reset_vector:
+	la sp, _fstack
+	la t0, trap_vector
+	csrw mtvec, t0
+
+	// initialize .data
+	la t0, _fdata
+	la t1, _edata
+	la t2, _fdata_rom
+1:	beq t0, t1, 2f
+	lw t3, 0(t2)
+	sw t3, 0(t0)
+	addi t0, t0, 4
+	addi t2, t2, 4
+	j 1b
+2:
+
+	// initialize .bss
+	la t0, _fbss
+	la t1, _ebss
+1:	beq t0, t1, 3f
+	sw zero, 0(t0)
+	addi t0, t0, 4
+	j 1b
+3:
+	// enable external interrupts
+	li t0, MIE_MEIE
+	csrs mie, t0
+
+	call main
+1:	j 1b
+
+trap_vector:
+	addi sp, sp, -16*4
+	sw ra,  0*4(sp)
+	sw t0,  1*4(sp)
+	sw t1,  2*4(sp)
+	sw t2,  3*4(sp)
+	sw a0,  4*4(sp)
+	sw a1,  5*4(sp)
+	sw a2,  6*4(sp)
+	sw a3,  7*4(sp)
+	sw a4,  8*4(sp)
+	sw a5,  9*4(sp)
+	sw a6, 10*4(sp)
+	sw a7, 11*4(sp)
+	sw t3, 12*4(sp)
+	sw t4, 13*4(sp)
+	sw t5, 14*4(sp)
+	sw t6, 15*4(sp)
+	call isr
+	lw ra,  0*4(sp)
+	lw t0,  1*4(sp)
+	lw t1,  2*4(sp)
+	lw t2,  3*4(sp)
+	lw a0,  4*4(sp)
+	lw a1,  5*4(sp)
+	lw a2,  6*4(sp)
+	lw a3,  7*4(sp)
+	lw a4,  8*4(sp)
+	lw a5,  9*4(sp)
+	lw a6, 10*4(sp)
+	lw a7, 11*4(sp)
+	lw t3, 12*4(sp)
+	lw t4, 13*4(sp)
+	lw t5, 14*4(sp)
+	lw t6, 15*4(sp)
+	addi sp, sp, 16*4
+	mret

litex/soc/cores/cpu/urv/irq.h

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+#ifndef __IRQ_H
+#define __IRQ_H
+
+#endif /* __IRQ_H */

litex/soc/cores/cpu/urv/system.h

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+#ifndef __SYSTEM_H
+#define __SYSTEM_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+__attribute__((unused)) static void flush_cpu_icache(void){}; /* No instruction cache */
+__attribute__((unused)) static void flush_cpu_dcache(void){}; /* No instruction cache */
+void flush_l2_cache(void);
+
+void busy_wait(unsigned int ms);
+void busy_wait_us(unsigned int us);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __SYSTEM_H */