MIPS: Make the kernel arguments from dtb available

Similar to how arm allows using selecting between bootloader arguments,
dtb arguments and both, allow to select them on mips. But since we have
less control over the place of the dtb do not modify it but instead use
the boot_command_line for merging them.

The default is "use bootloader arguments" to keep the current behaviour
as default.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: John Crispin <blogic@openwrt.org>
Cc: Ganesan Ramalingam <ganesanr@broadcom.com>
Cc: Jayachandran C <jchandra@broadcom.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: James Hartley <james.hartley@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11284/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -2749,6 +2749,22 @@ choice
 		  if you don't intend to always append a DTB.
 endchoice
 
+choice
+	prompt "Kernel command line type" if !CMDLINE_OVERRIDE
+	default MIPS_CMDLINE_FROM_BOOTLOADER
+
+	config MIPS_CMDLINE_FROM_DTB
+		depends on USE_OF
+		bool "Dtb kernel arguments if available"
+
+	config MIPS_CMDLINE_DTB_EXTEND
+		depends on USE_OF
+		bool "Extend dtb kernel arguments with bootloader arguments"
+
+	config MIPS_CMDLINE_FROM_BOOTLOADER
+		bool "Bootloader kernel arguments if available"
+endchoice
+
 endmenu
 
 config LOCKDEP_SUPPORT

arch/mips/kernel/setup.c

@@ -617,6 +617,10 @@ static void __init request_crashkernel(struct resource *res)
 }
 #endif /* !defined(CONFIG_KEXEC)  */
 
+#define USE_PROM_CMDLINE	IS_ENABLED(CONFIG_MIPS_CMDLINE_FROM_BOOTLOADER)
+#define USE_DTB_CMDLINE		IS_ENABLED(CONFIG_MIPS_CMDLINE_FROM_DTB)
+#define EXTEND_WITH_PROM	IS_ENABLED(CONFIG_MIPS_CMDLINE_EXTEND)
+
 static void __init arch_mem_init(char **cmdline_p)
 {
 	struct memblock_region *reg;
@@ -641,18 +645,24 @@ static void __init arch_mem_init(char **cmdline_p)
 	pr_info("Determined physical RAM map:\n");
 	print_memory_map();
 
-#ifdef CONFIG_CMDLINE_BOOL
-#ifdef CONFIG_CMDLINE_OVERRIDE
+#if defined(CONFIG_CMDLINE_BOOL) && defined(CONFIG_CMDLINE_OVERRIDE)
 	strlcpy(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 #else
+	if ((USE_PROM_CMDLINE && arcs_cmdline[0]) ||
+	    (USE_DTB_CMDLINE && !boot_command_line[0]))
+		strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
+
+	if (EXTEND_WITH_PROM && arcs_cmdline[0]) {
+		strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
+	}
+
+#if defined(CONFIG_CMDLINE_BOOL)
 	if (builtin_cmdline[0]) {
-		strlcat(arcs_cmdline, " ", COMMAND_LINE_SIZE);
-		strlcat(arcs_cmdline, builtin_cmdline, COMMAND_LINE_SIZE);
+		strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
+		strlcat(boot_command_line, builtin_cmdline, COMMAND_LINE_SIZE);
 	}
-	strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
 #endif
-#else
-	strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
 #endif
 	strlcpy(command_line, boot_command_line, COMMAND_LINE_SIZE);