MIPS: Add support for vmlinux.bin appended dtb

Add support for detecting a vmlinux.bin appended dtb and overriding
the boot arguments to match the UHI interface.

Due to the PERCPU section being empty for !SMP, but still modifying
the current address by aligning it to the page size, do not define
it for !SMP builds to allow __appended_dtb to still point to
the actual end of the data.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: John Crispin <blogic@openwrt.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: James Hartley <James.Hartley@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/9739/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 164d8c73552fff501f34e1dc2c75ae8ffcbc189f..7cb5f6dbaeeeb55fbc4c221ae889a3f213e7f2f1 100644 (file)
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2677,6 +2677,33 @@ config USE_OF
 config BUILTIN_DTB
        bool
 
+choice
+       prompt "Kernel appended dtb support" if OF
+       default MIPS_NO_APPENDED_DTB
+
+       config MIPS_NO_APPENDED_DTB
+               bool "None"
+               help
+                 Do not enable appended dtb support.
+
+       config MIPS_RAW_APPENDED_DTB
+               bool "vmlinux.bin"
+               help
+                 With this option, the boot code will look for a device tree binary
+                 DTB) appended to raw vmlinux.bin (without decompressor).
+                 (e.g. cat vmlinux.bin <filename>.dtb > vmlinux_w_dtb).
+
+                 This is meant as a backward compatibility convenience for those
+                 systems with a bootloader that can't be upgraded to accommodate
+                 the documented boot protocol using a device tree.
+
+                 Beware that there is very little in terms of protection against
+                 this option being confused by leftover garbage in memory that might
+                 look like a DTB header after a reboot if no actual DTB is appended
+                 to vmlinux.bin.  Do not leave this option active in a production kernel
+                 if you don't intend to always append a DTB.
+endchoice
+
 endmenu
 
 config LOCKDEP_SUPPORT

diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
index 95afd663cd459b873d31401b9916b27b2f653b16..4e4cc5b9a7714e78c8d4b3b5ac3f2c2eeba5c5c2 100644 (file)
--- a/arch/mips/kernel/head.S
+++ b/arch/mips/kernel/head.S
@@ -94,6 +94,22 @@ NESTED(kernel_entry, 16, sp)                 # kernel entry point
        jr      t0
 0:
 
+#ifdef CONFIG_MIPS_RAW_APPENDED_DTB
+       PTR_LA          t0, __appended_dtb
+
+#ifdef CONFIG_CPU_BIG_ENDIAN
+       li              t1, 0xd00dfeed
+#else
+       li              t1, 0xedfe0dd0
+#endif
+       lw              t2, (t0)
+       bne             t1, t2, not_found
+        nop
+
+       move            a1, t0
+       PTR_LI          a0, -2
+not_found:
+#endif
        PTR_LA          t0, __bss_start         # clear .bss
        LONG_S          zero, (t0)
        PTR_LA          t1, __bss_stop - LONGSIZE

diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 3b46f7ce9ca75bc5f81f9bb2939880277289bd20..07d32a4aea60e418892ffb27cbae05c11099a92f 100644 (file)
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -125,8 +125,14 @@ SECTIONS
        .exit.data : {
                EXIT_DATA
        }
-
+#ifdef CONFIG_SMP
        PERCPU_SECTION(1 << CONFIG_MIPS_L1_CACHE_SHIFT)
+#endif
+#ifdef CONFIG_MIPS_RAW_APPENDED_DTB
+       __appended_dtb = .;
+       /* leave space for appended DTB */
+       . += 0x100000;
+#endif
        /*
         * Align to 64K in attempt to eliminate holes before the
         * .bss..swapper_pg_dir section at the start of .bss.  This