Porting barebox to a new SoC

[Lior Weintraub <liorw@pliops.com>]

Hi,

I tried to follow the porting guide on https://www.barebox.org/doc/latest/devel/porting.html# but couldn't follow the instructions.
I would like to port barebox to a new SoC (which is not a derivative of any known SoC).
It has the following:
* Single Cortex A53
* SRAM (4MB) located on address 0xC000000000

The below patch shows my initial test to try and have a starting point.
I am setting env variables:
export ARCH=arm64 
export CROSS_COMPILE=/home/pliops/workspace/ARM/arm-gnu-toolchain/bin/aarch64-none-elf-

Then I build with:
make spider_defconfig && make

This gives an error:
aarch64-none-elf-gcc: error: unrecognized argument in option '-mabi=apcs-gnu'
aarch64-none-elf-gcc: note: valid arguments to '-mabi=' are: ilp32 lp64
aarch64-none-elf-gcc: error: unrecognized command-line option '-msoft-float'
aarch64-none-elf-gcc: error: unrecognized command-line option '-mno-unaligned-access'
/home/pliops/workspace/simplest-linux-demo/barebox/scripts/Makefile.build:140: recipe for target 'scripts/mod/empty.o' failed
make[2]: *** [scripts/mod/empty.o] Error 1

Not sure why the compiler flags get -mabi=apcs-gnu when I explicitly set CONFIG_CPU_V8 and the arch/arm/Makefile has:
ifeq ($(CONFIG_CPU_V8), y)
CFLAGS_ABI	:=-mabi=lp64


The changes I did:
>From 848b5f9b18bb1bb96d197cbc1b368ee0a729d581 Mon Sep 17 00:00:00 2001
From: Lior Weintraub <liorw@pliops.com>
Date: Sun, 28 May 2023 15:51:44 +0300
Subject: [PATCH 1/1] Initial Pliops Spider board

---
 arch/arm/boards/pliops/spider/Makefile   |  4 ++++
 arch/arm/boards/pliops/spider/board.c    | 26 ++++++++++++++++++++++
 arch/arm/boards/pliops/spider/lowlevel.c | 28 ++++++++++++++++++++++++
 arch/arm/configs/spider_defconfig        |  3 +++
 4 files changed, 61 insertions(+)
 create mode 100644 arch/arm/boards/pliops/spider/Makefile
 create mode 100644 arch/arm/boards/pliops/spider/board.c
 create mode 100644 arch/arm/boards/pliops/spider/lowlevel.c
 create mode 100644 arch/arm/configs/spider_defconfig

diff --git a/arch/arm/boards/pliops/spider/Makefile b/arch/arm/boards/pliops/spider/Makefile
new file mode 100644
index 0000000000..da63d2625f
--- /dev/null
+++ b/arch/arm/boards/pliops/spider/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-y += board.o
+lwl-y += lowlevel.o
diff --git a/arch/arm/boards/pliops/spider/board.c b/arch/arm/boards/pliops/spider/board.c
new file mode 100644
index 0000000000..17cdd5e2b9
--- /dev/null
+++ b/arch/arm/boards/pliops/spider/board.c
@@ -0,0 +1,26 @@
+#include <bbu.h>
+#include <boot.h>
+#include <bootm.h>
+#include <common.h>
+#include <deep-probe.h>
+#include <environment.h>
+#include <fcntl.h>
+#include <globalvar.h>
+
+static int spider_board_probe(struct device *dev)
+{
+      /* Do some board-specific setup */
+      return 0;
+}
+
+static const struct of_device_id spider_board_of_match[] = {
+      { .compatible = "spider,spider-board" },
+      { /* sentinel */ },
+};
+
+static struct driver spider_board_driver = {
+      .name = "board-spider",
+      .probe = spider_board_probe,
+      .of_compatible = spider_board_of_match,
+};
+device_platform_driver(spider_board_driver);
\ No newline at end of file
diff --git a/arch/arm/boards/pliops/spider/lowlevel.c b/arch/arm/boards/pliops/spider/lowlevel.c
new file mode 100644
index 0000000000..f3d5a27647
--- /dev/null
+++ b/arch/arm/boards/pliops/spider/lowlevel.c
@@ -0,0 +1,28 @@
+#include <common.h>
+#include <asm/barebox-arm.h>
+
+#define BASE_ADDR       (0xD000307000)
+#define GPRAM_ADDR      (0xC000000000)
+#define MY_STACK_TOP    (0xC000000000 + SZ_2M) // Set the stack 2MB from GPRAM start (excatly in the middle)
+static inline void spider_serial_putc(void *base, int c)
+{
+//     if (!(readl(base + UCR1) & UCR1_UARTEN))
+//             return;
+//
+//     while (!(readl(base + USR2) & USR2_TXDC));
+//
+//     writel(c, base + URTX0);
+}
+
+ENTRY_FUNCTION_WITHSTACK(start_spider_board, MY_STACK_TOP, r0, r1, r2)
+{
+       extern char __dtb_spider_board_start[];
+       void *fdt;
+
+       relocate_to_current_adr();
+       setup_c();
+
+       pbl_set_putc(spider_serial_putc, (void *)BASE_ADDR);
+
+       barebox_arm_entry(GPRAM_ADDR, SZ_2M, __dtb_spider_board_start);
+}
diff --git a/arch/arm/configs/spider_defconfig b/arch/arm/configs/spider_defconfig
new file mode 100644
index 0000000000..b4c4a32de0
--- /dev/null
+++ b/arch/arm/configs/spider_defconfig
@@ -0,0 +1,3 @@
+CONFIG_TEXT_BASE=0x4000000000
+CONFIG_64BIT=y
+CONFIG_CPU_V8=y
-- 
2.40.0


Appreciate your kind advise,
Cheers,
Lior.