BACKPORT: MIPS: store the appended dtb address in a variable

Instead of rewriting the arguments to match the UHI spec, store the
address of a appended or UHI supplied dtb in fw_supplied_dtb.

That way the original bootloader arugments are kept intact while still
making the use of an appended dtb invisible for mach code.

Mach code can still find out if it is an appended dtb by comparing
fw_arg1 with fw_supplied_dtb.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: John Crispin <john@phrozen.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Alban Bedel <albeu@free.fr>
Cc: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>
Cc: Antony Pavlov <antonynpavlov@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13699/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
(cherry picked from commit 15f37e1588920e010f20b53f04af94e91b8ee714)

Conflicts:
	arch/mips/ath79/setup.c
	arch/mips/lantiq/prom.c
	arch/mips/pic32/pic32mzda/init.c
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

4 files changed, 24 insertions, 9 deletions

diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index 5b16d2955fbb..a2a8344b8a64 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -149,8 +149,8 @@ void __init plat_mem_setup(void)
 	/* intended to somewhat resemble ARM; see Documentation/arm/Booting */
 	if (fw_arg0 == 0 && fw_arg1 == 0xffffffff)
 		dtb = phys_to_virt(fw_arg2);
-	else if (fw_arg0 == -2) /* UHI interface */
-		dtb = (void *)fw_arg1;
+	else if (fw_passed_dtb) /* UHI interface */
+		dtb = (void *)fw_passed_dtb;
 	else if (__dtb_start != __dtb_end)
 		dtb = (void *)__dtb_start;
 	else
diff --git a/arch/mips/include/asm/bootinfo.h b/arch/mips/include/asm/bootinfo.h
index b603804caac5..6effbf5c71ec 100644
--- a/arch/mips/include/asm/bootinfo.h
+++ b/arch/mips/include/asm/bootinfo.h
@@ -127,6 +127,10 @@ extern char arcs_cmdline[COMMAND_LINE_SIZE];
  */
 extern unsigned long fw_arg0, fw_arg1, fw_arg2, fw_arg3;
 
+#ifdef CONFIG_USE_OF
+extern unsigned long fw_passed_dtb;
+#endif
+
 /*
  * Platform memory detection hook called by setup_arch
  */
diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
index 4e4cc5b9a771..462989e89ec9 100644
--- a/arch/mips/kernel/head.S
+++ b/arch/mips/kernel/head.S
@@ -94,21 +94,24 @@ NESTED(kernel_entry, 16, sp)			# kernel entry point
 	jr	t0
 0:
 
+#ifdef CONFIG_USE_OF
 #ifdef CONFIG_MIPS_RAW_APPENDED_DTB
-	PTR_LA		t0, __appended_dtb
+	PTR_LA		t2, __appended_dtb
 
 #ifdef CONFIG_CPU_BIG_ENDIAN
 	li		t1, 0xd00dfeed
 #else
 	li		t1, 0xedfe0dd0
 #endif
-	lw		t2, (t0)
-	bne		t1, t2, not_found
-	 nop
+	lw		t0, (t2)
+	beq		t0, t1, dtb_found
+#endif
+	li		t1, -2
+	beq		a0, t1, dtb_found
+	move		t2, a1
 
-	move		a1, t0
-	PTR_LI		a0, -2
-not_found:
+	li		t2, 0
+dtb_found:
 #endif
 	PTR_LA		t0, __bss_start		# clear .bss
 	LONG_S		zero, (t0)
@@ -123,6 +126,10 @@ not_found:
 	LONG_S		a2, fw_arg2
 	LONG_S		a3, fw_arg3
 
+#ifdef CONFIG_USE_OF
+	LONG_S		t2, fw_passed_dtb
+#endif
+
 	MTC0		zero, CP0_CONTEXT	# clear context register
 	PTR_LA		$28, init_thread_union
 	/* Set the SP after an empty pt_regs.  */
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 4f9f1ae49213..ac010f157763 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -886,6 +886,10 @@ void __init setup_arch(char **cmdline_p)
 unsigned long kernelsp[NR_CPUS];
 unsigned long fw_arg0, fw_arg1, fw_arg2, fw_arg3;
 
+#ifdef CONFIG_USE_OF
+unsigned long fw_passed_dtb;
+#endif
+
 #ifdef CONFIG_DEBUG_FS
 struct dentry *mips_debugfs_dir;
 static int __init debugfs_mips(void)