From 7f21c93c332e766644252371c6b8f383abb6ea97 Mon Sep 17 00:00:00 2001
From: Mike Walters <mike@flomp.net>
Date: Wed, 6 Oct 2021 18:33:46 +0100
Subject: [PATCH] Copy M0 image directly from ROM, instead of shadow region.

This changes m0_rom_to_ram to read directly from the ROM region, rather
than copying from where .text has been copied to RAM.

Previously the second .text section would be merged with the first one,
so the M0 image would be copied to RAM during `pre_main`. However, on
newer linkers the sections are not merged together so the second .text
section did not get copied to RAM.

fixes #936
---
 .../common/LPC43xx_M4_M0_image_from_text.ld   |  2 +-
 firmware/hackrf_usb/hackrf_usb.c              | 23 ++++++++++++-------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/firmware/common/LPC43xx_M4_M0_image_from_text.ld b/firmware/common/LPC43xx_M4_M0_image_from_text.ld
index 3c61f69e..38b5e769 100644
--- a/firmware/common/LPC43xx_M4_M0_image_from_text.ld
+++ b/firmware/common/LPC43xx_M4_M0_image_from_text.ld
@@ -22,7 +22,7 @@
 
 SECTIONS
 {
-	.text : {
+	.m0_text : {
 		PROVIDE(__m0_start__ = .);
 		KEEP(*(.m0_bin*));
 		. = ALIGN(4);
diff --git a/firmware/hackrf_usb/hackrf_usb.c b/firmware/hackrf_usb/hackrf_usb.c
index f468fc1d..b7b8c01e 100644
--- a/firmware/hackrf_usb/hackrf_usb.c
+++ b/firmware/hackrf_usb/hackrf_usb.c
@@ -21,6 +21,7 @@
  */
 
 #include <stddef.h>
+#include <string.h>
 
 #include <libopencm3/lpc43xx/ipc.h>
 #include <libopencm3/lpc43xx/m4/nvic.h>
@@ -56,6 +57,7 @@
 extern uint32_t __m0_start__;
 extern uint32_t __m0_end__;
 extern uint32_t __ram_m0_start__;
+extern uint32_t _etext_ram, _text_ram, _etext_rom;
 
 static usb_request_handler_fn vendor_request_handler[] = {
 	NULL,
@@ -188,16 +190,21 @@ static bool cpld_jtag_sram_load(jtag_t* const jtag) {
 
 static void m0_rom_to_ram() {
 	uint32_t *dest = &__ram_m0_start__;
-	uint32_t *src = &__m0_start__;
-	while (src < &__m0_end__) {
-		*dest = *src;
-		dest++;
-		src++;
-	}
+
+	// Calculate the base address of ROM
+	uint32_t base = (uint32_t)(&_etext_rom - (&_etext_ram - &_text_ram));
+
+	// M0 image location, relative to the start of ROM
+	uint32_t src = (uint32_t)&__m0_start__;
+
+	uint32_t len = (uint32_t)&__m0_end__ - (uint32_t)src;
+	memcpy(dest, (uint32_t*)(base + src), len);
 }
 
 int main(void) {
-	bool operacake_allow_gpio;
+	// Copy M0 image from ROM before SPIFI is disabled
+	m0_rom_to_ram();
+
 	pin_setup();
 	enable_1v8_power();
 #if (defined HACKRF_ONE || defined RAD1O)
@@ -209,7 +216,6 @@ int main(void) {
 	cpu_clock_init();
 
 	/* Wake the M0 */
-	m0_rom_to_ram();
 	ipc_start_m0((uint32_t)&__ram_m0_start__);
 
 	if( !cpld_jtag_sram_load(&jtag_cpld) ) {
@@ -245,6 +251,7 @@ int main(void) {
 	
 	rf_path_init(&rf_path);
 
+	bool operacake_allow_gpio;
 	if( hackrf_ui()->operacake_gpio_compatible() ) {
 		operacake_allow_gpio = true;
 	} else {