RISC-V: add LiteX SoC and linux-on-litex-vexriscv support

LiteX is a Migen-based System on Chip, supporting softcore
VexRiscv CPU, a 32-bits Linux Capable RISC-V CPU.

See https://github.com/enjoy-digital/litex and
https://github.com/litex-hub/linux-on-litex-vexriscv
for details.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Acked-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20210817101104.114945-8-antonynpavlov@gmail.com
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

9 files changed, 308 insertions, 0 deletions

diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
index 221ea133d4..5c281918d5 100644
--- a/arch/riscv/Kconfig.socs
+++ b/arch/riscv/Kconfig.socs
@@ -95,4 +95,18 @@ config SIFIVE_L2
 	bool "SiFive L2 cache controller"
 	depends on CPU_SIFIVE
 
+config SOC_LITEX
+	bool "LiteX SoCs"
+	depends on ARCH_RV32I
+	select HAS_ASM_DEBUG_LL
+	select HAS_NMON
+	select USE_COMPRESSED_DTB
+	select RISCV_TIMER
+
+config BOARD_LITEX_LINUX
+	bool "litex linux board"
+	depends on SOC_LITEX
+	select RISCV_M_MODE
+	def_bool y
+
 endmenu
diff --git a/arch/riscv/boards/Makefile b/arch/riscv/boards/Makefile
index cb28a25d8b..8d5d9d4fc6 100644
--- a/arch/riscv/boards/Makefile
+++ b/arch/riscv/boards/Makefile
@@ -2,3 +2,4 @@
 obj-$(CONFIG_BOARD_ERIZO_GENERIC)	+= erizo/
 obj-$(CONFIG_BOARD_HIFIVE)		+= hifive/
 obj-$(CONFIG_BOARD_BEAGLEV)		+= beaglev/
+obj-$(CONFIG_BOARD_LITEX_LINUX)		+= litex-linux/
diff --git a/arch/riscv/boards/litex-linux/Makefile b/arch/riscv/boards/litex-linux/Makefile
new file mode 100644
index 0000000000..3d217ffe0b
--- /dev/null
+++ b/arch/riscv/boards/litex-linux/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+pbl-y += lowlevel.o
diff --git a/arch/riscv/boards/litex-linux/lowlevel.c b/arch/riscv/boards/litex-linux/lowlevel.c
new file mode 100644
index 0000000000..da23ef5633
--- /dev/null
+++ b/arch/riscv/boards/litex-linux/lowlevel.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <common.h>
+#include <asm/barebox-riscv.h>
+#include <debug_ll.h>
+#include <asm/riscv_nmon.h>
+
+ENTRY_FUNCTION(start_litex_linux, a0, a1, a2)
+{
+	extern char __dtb_z_litex_linux_start[];
+	void *fdt;
+
+	barebox_nmon_entry();
+
+	putc_ll('>');
+
+	/* On POR, we are running from read-only memory here. */
+
+	fdt = __dtb_z_litex_linux_start + get_runtime_offset();
+
+	barebox_riscv_machine_entry(0x40000000, SZ_256M, fdt);
+}
diff --git a/arch/riscv/dts/Makefile b/arch/riscv/dts/Makefile
index 4a15423b7f..17d7d249e4 100644
--- a/arch/riscv/dts/Makefile
+++ b/arch/riscv/dts/Makefile
@@ -8,5 +8,6 @@ pbl-$(CONFIG_BOARD_ERIZO_GENERIC) += erizo-generic.dtb.o
 pbl-$(CONFIG_BOARD_HIFIVE) += hifive-unmatched-a00.dtb.o \
                               hifive-unleashed-a00.dtb.o
 pbl-$(CONFIG_BOARD_BEAGLEV) += jh7100-beaglev-starlight.dtb.o
+pbl-$(CONFIG_BOARD_LITEX_LINUX) += litex-linux.dtb.o
 
 clean-files := *.dtb *.dtb.S .*.dtc .*.pre .*.dts
diff --git a/arch/riscv/dts/litex-linux.dts b/arch/riscv/dts/litex-linux.dts
new file mode 100644
index 0000000000..d21fa57e30
--- /dev/null
+++ b/arch/riscv/dts/litex-linux.dts
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "litex_soc_linux.dtsi"
+
+#include <dt-bindings/gpio/gpio.h>
+
+/ {
+	model = "LiteX VexRiscV-SoC-Linux";
+	compatible = "litex,vexriscv-soc-linux";
+
+	aliases {
+		rom = &rom;
+		sram = &sram;
+	};
+
+	/* ARTY board */
+	rom: rom@00000000 {
+		compatible = "mmio-sram";
+		reg = <0x00000000 0x00008000>;
+		read-only;
+	};
+
+	sram: sram@20000000 {
+		compatible = "mmio-sram";
+		reg = <0x20000000 0x00004000>;
+	};
+
+	main_ram: memory@40000000 {
+		device_type = "memory";
+		reg = <0x40000000 0x10000000>;
+	};
+};
+
+&uart0 {
+	status = "okay";
+};
+
+&mac0 {
+	status = "okay";
+};
+
+&spi0 {
+	status = "okay";
+
+	spiflash: w25q128@0 {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		compatible = "winbond,w25q128", "jedec,spi-nor";
+		spi-max-frequency = <104000000>;
+		reg = <0>;
+	};
+};
+
+/ {
+	ledsgpio: gpio@f000a800 {
+		compatible = "ti,74175";
+		reg = <0xf000a800 0x4>;
+		gpio-controller;
+		#gpio-cells = <2>;
+	};
+
+	leds {
+		compatible = "gpio-leds";
+
+		ld0 {
+			label = "arty:green:ld0";
+			gpios = <&ledsgpio 0 GPIO_ACTIVE_HIGH>;
+		};
+
+		ld1 {
+			label = "arty:green:ld1";
+			gpios = <&ledsgpio 1 GPIO_ACTIVE_HIGH>;
+		};
+
+		ld2 {
+			label = "arty:green:ld2";
+			gpios = <&ledsgpio 2 GPIO_ACTIVE_HIGH>;
+		};
+
+		ld3 {
+			label = "arty:green:ld3";
+			gpios = <&ledsgpio 3 GPIO_ACTIVE_HIGH>;
+		};
+	};
+
+	swgpio: gpio@f0006000 {
+		compatible = "ti,74125";
+		reg = <0xf0006000 0x4>;
+		gpio-controller;
+		#gpio-cells = <2>;
+	};
+};
diff --git a/arch/riscv/dts/litex_soc_linux.dtsi b/arch/riscv/dts/litex_soc_linux.dtsi
new file mode 100644
index 0000000000..94a0ba29da
--- /dev/null
+++ b/arch/riscv/dts/litex_soc_linux.dtsi
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/dts-v1/;
+
+/ {
+	compatible = "litex,vexriscv-soc-linux";
+
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		timebase-frequency = <100000000>; // 100 MHz
+
+		cpu@0 {
+			device_type = "cpu";
+			compatible = "spinalhdl,vexriscv", "riscv";
+			reg = <0>;
+		};
+	};
+
+	uart0: serial@f0001000 {
+		compatible = "litex,uart";
+		reg = <0xf0001000 0x18>;
+		status = "disabled";
+	};
+
+	mac0: mac@f0006800 {
+		compatible = "litex,liteeth";
+		reg = <0xf0006800 0x7c /* base */
+			0xf0007000 0x0a /* mdio_base */
+			0xb0000000 0x2000>; /* buf_base */
+		tx-fifo-depth = <2>;
+		rx-fifo-depth = <2>;
+		status = "disabled";
+	};
+
+	spi0: spi@f000b800 {
+		compatible = "litex,spiflash";
+
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		reg = <0xf000b800 0x100>;
+		status = "disabled";
+	};
+};
diff --git a/arch/riscv/include/asm/debug_ll.h b/arch/riscv/include/asm/debug_ll.h
index b4caa0597a..a3b9c1c4bc 100644
--- a/arch/riscv/include/asm/debug_ll.h
+++ b/arch/riscv/include/asm/debug_ll.h
@@ -43,6 +43,9 @@ static inline void PUTC_LL(char ch)
 
 	writel(ch, uart0);
 }
+#elif defined CONFIG_DEBUG_LITEX
+
+#include <asm/debug_ll_litex.h>
 
 #endif
 
diff --git a/arch/riscv/include/asm/debug_ll_litex.h b/arch/riscv/include/asm/debug_ll_litex.h
new file mode 100644
index 0000000000..2fcdd9b0ec
--- /dev/null
+++ b/arch/riscv/include/asm/debug_ll_litex.h
@@ -0,0 +1,123 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2019 Antony Pavlov <antonynpavlov@gmail.com>
+ *
+ * This file is part of barebox.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __ASM_DEBUG_LL_LITEX__
+#define __ASM_DEBUG_LL_LITEX__
+
+/** @file
+ *  This File contains declaration for early output support
+ */
+
+#include <linux/kconfig.h>
+
+#define DEBUG_LL_UART_ADDR	0xf0001000
+#define UART_RXTX	0x00
+#define UART_TXFULL	0x04
+#define UART_RXEMPTY	0x08
+#define UART_EV_PENDING	0x10
+#define  UART_EV_RX	(1 << 1)
+
+
+#ifndef __ASSEMBLY__
+
+/*
+ * C macros
+ */
+
+#include <asm/io.h>
+
+static inline void PUTC_LL(char ch)
+{
+#ifdef CONFIG_DEBUG_LL
+	/* wait for space */
+	while (__raw_readb((u8 *)DEBUG_LL_UART_ADDR + UART_TXFULL))
+		;
+
+	__raw_writeb(ch, (u8 *)DEBUG_LL_UART_ADDR + UART_RXTX);
+#endif /* CONFIG_DEBUG_LL */
+}
+#else /* __ASSEMBLY__ */
+/*
+ * Macros for use in assembly language code
+ */
+
+/*
+ * output a character in a0
+ */
+.macro	debug_ll_outc_a0
+#ifdef CONFIG_DEBUG_LL
+
+	li	t0, DEBUG_LL_UART_ADDR
+
+201:
+	lbu	t1, UART_TXFULL(t0)	/* uart tx full ? */
+	andi	t1, t1, 0xff
+	bnez	t1, 201b		/* try again */
+
+	sb	a0, UART_RXTX(t0)	/* write the character */
+
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * output a character
+ */
+.macro	debug_ll_outc chr
+#ifdef CONFIG_DEBUG_LL
+	li	a0, \chr
+	debug_ll_outc_a0
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * check character in input buffer
+ * return value:
+ *  v0 = 0   no character in input buffer
+ *  v0 != 0  character in input buffer
+ */
+.macro	debug_ll_tstc
+#ifdef CONFIG_DEBUG_LL
+	li	t0, DEBUG_LL_UART_ADDR
+
+	/* get line status and check for data present */
+	lbu	s0, UART_RXEMPTY(t0)
+	bnez    s0, 243f
+	li	s0, 1
+	j	244f
+243:	li	s0, 0
+244:	nop
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * get character to v0
+ */
+.macro	debug_ll_getc
+#ifdef CONFIG_DEBUG_LL
+
+204:
+	debug_ll_tstc
+
+	/* try again */
+	beqz	s0, 204b
+
+	/* read a character */
+	lb	s0, UART_RXTX(t0)
+	li      t1, UART_EV_RX
+	sb	t1, UART_EV_PENDING(t0)
+
+#endif /* CONFIG_DEBUG_LL */
+.endm
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_DEBUG_LL_LITEX__ */