ARC: [cmdline] support External Device Trees from u-boot

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index ffb60b4f6f86..119dddb752b2 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -323,22 +323,31 @@ static inline int is_kernel(unsigned long addr)
 
 void __init setup_arch(char **cmdline_p)
 {
+        /* make sure that uboot passed pointer to cmdline/dtb is valid */
+        if (uboot_tag && is_kernel((unsigned long)uboot_arg))
+                panic("Invalid uboot arg\n");
+
+        /* See if u-boot passed an external Device Tree blob */
+        machine_desc = setup_machine_fdt(uboot_arg);    /* uboot_tag == 2 */
+        if (!machine_desc) {
+                /* No, so try the embedded one */
                 machine_desc = setup_machine_fdt(__dtb_start);
                 if (!machine_desc)
                         panic("Embedded DT invalid\n");
 
                 /*
-                 * Append uboot cmdline to embedded DT cmdline.
+                 * If we are here, it is established that @uboot_arg didn't
+                 * point to DT blob. Instead if u-boot says it is cmdline,
+                 * Appent to embedded DT cmdline.
                  * setup_machine_fdt() would have populated @boot_command_line
                  */
                 if (uboot_tag == 1) {
-                        BUG_ON(is_kernel(unsigned long)uboot_arg);
-
                         /* Ensure a whitespace between the 2 cmdlines */
                         strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
                         strlcat(boot_command_line, uboot_arg,
                                 COMMAND_LINE_SIZE);
                 }
+        }
 
         /* Save unparsed command line copy for /proc/cmdline */
         *cmdline_p = boot_command_line;