of/fdt: run soc memory setup when early_init_dt_scan_memory fails

If memory has been found early_init_dt_scan_memory now returns 1. If
it hasn't found any memory it will return 0, allowing other memory
setup mechanisms to carry on.

Previously early_init_dt_scan_memory always returned 0 without
distinguishing between any kind of memory setup being done or not. Any
code path after the early_init_dt_scan memory call in the ramips
plat_mem_setup code wouldn't be executed anymore. Making
early_init_dt_scan_memory the only way to initialize the memory.

Some boards, including my mt7621 based Cudy X6 board, depend on memory
initialization being done via the soc_info.mem_detect function
pointer. Those wouldn't be able to obtain memory and panic the kernel
during early bootup with the message "early_init_dt_alloc_memory_arch:
Failed to allocate 12416 bytes align=0x40".

Fixes: 1f012283 ("of/fdt: Rework early_init_dt_scan_memory() to call directly")
Cc: stable@vger.kernel.org
Signed-off-by: Andreas Rammhold <andreas@rammhold.de>
Link: https://lore.kernel.org/r/20221223112748.2935235-1-andreas@rammhold.deSigned-off-by: Rob Herring <robh@kernel.org>

arch/mips/ralink/of.c

@@ -64,7 +64,7 @@ void __init plat_mem_setup(void)
 	dtb = get_fdt();
 	__dt_setup_arch(dtb);
 
-	if (!early_init_dt_scan_memory())
+	if (early_init_dt_scan_memory())
 		return;
 
 	if (soc_info.mem_detect)

drivers/of/fdt.c

@@ -1099,7 +1099,7 @@ u64 __init dt_mem_next_cell(int s, const __be32 **cellp)
  */
 int __init early_init_dt_scan_memory(void)
 {
-	int node;
+	int node, found_memory = 0;
 	const void *fdt = initial_boot_params;
 
 	fdt_for_each_subnode(node, fdt, 0) {
@@ -1139,6 +1139,8 @@ int __init early_init_dt_scan_memory(void)
 
 			early_init_dt_add_memory_arch(base, size);
 
+			found_memory = 1;
+
 			if (!hotpluggable)
 				continue;
 
@@ -1147,7 +1149,7 @@ int __init early_init_dt_scan_memory(void)
 					base, base + size);
 		}
 	}
-	return 0;
+	return found_memory;
 }
 
 int __init early_init_dt_scan_chosen(char *cmdline)