microblaze: Setup initrd_high and fdt_high at run time

Setup initrd_high and fdt_high to be placed in lowmem space for kernel to
be able to reach it. Values are setup at run time to ensure that the same
setting can be used on different memory setup. Do this setting only when
variables are not

Similar run time detection was done for Zynqmp and Versal.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/Kconfig

@@ -20,6 +20,14 @@ config TARGET_MICROBLAZE_GENERIC
 
 endchoice
 
+config STACK_SIZE
+	hex "Define max stack size that can be used by u-boot"
+	default 0x200000
+	help
+	  Defines Max stack size that can be used by u-boot so that the
+	  initrd_high will be calculated as base stack pointer minus this
+	  stack size.
+
 source "board/xilinx/microblaze-generic/Kconfig"
 
 config SPL_LDSCRIPT

board/xilinx/microblaze-generic/microblaze-generic.c

@@ -21,6 +21,7 @@
 #include <asm/gpio.h>
 #include <dm/uclass.h>
 #include <wdt.h>
+#include <linux/sizes.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -39,6 +40,8 @@ int dram_init(void)
 
 int board_late_init(void)
 {
+	ulong max_size, lowmem_size;
+
 #if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_SYSRESET_MICROBLAZE)
 	int ret;
 
@@ -47,5 +50,21 @@ int board_late_init(void)
 	if (ret)
 		printf("Warning: No reset driver: ret=%d\n", ret);
 #endif
+
+	if (!(gd->flags & GD_FLG_ENV_DEFAULT)) {
+		debug("Saved variables - Skipping\n");
+		return 0;
+	}
+
+	max_size = gd->start_addr_sp - CONFIG_STACK_SIZE;
+	max_size = round_down(max_size, SZ_16M);
+
+	/* Linux default LOWMEM_SIZE is 0x30000000 = 768MB */
+	lowmem_size = gd->ram_base + 768 * 1024 * 1024;
+
+	env_set_addr("initrd_high", (void *)min_t(ulong, max_size,
+						  lowmem_size));
+	env_set_addr("fdt_high", (void *)min_t(ulong, max_size, lowmem_size));
+
 	return 0;
 }