linux: add support of Synopsys ARC770-based boards

[openwrt/svn-archive/archive.git] / target / linux / arc770 / patches-4.3 / 0002-openwrt-arc-add-OWRTDTB-section.patch

diff --git a/target/linux/arc770/patches-4.3/0002-openwrt-arc-add-OWRTDTB-section.patch b/target/linux/arc770/patches-4.3/0002-openwrt-arc-add-OWRTDTB-section.patch
new file mode 100644 (file)
index 0000000..ddb426f
--- /dev/null
+++ b/target/linux/arc770/patches-4.3/0002-openwrt-arc-add-OWRTDTB-section.patch
@@ -0,0 +1,91 @@
+From 142abc9f7b8860638e39cf3850cf7ba328c26b42 Mon Sep 17 00:00:00 2001
+From: Alexey Brodkin <abrodkin@synopsys.com>
+Date: Sat, 31 Oct 2015 15:58:20 +0300
+Subject: [PATCH] openwrt: arc - add OWRTDTB section
+
+This change allows OpenWRT to patch resulting kernel binary with
+external .dtb.
+
+That allows us to re-use exactky the same vmlinux on different boards
+given its ARC core configurations match (at least cache line sizes etc).
+
+""patch-dtb" searches for ASCII "OWRTDTB:" strign and copies external
+.dtb right after it, keeping the string in place.
+
+Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
+---
+ arch/arc/kernel/head.S        | 10 ++++++++++
+ arch/arc/kernel/setup.c       |  4 +++-
+ arch/arc/kernel/vmlinux.lds.S | 13 +++++++++++++
+ 3 files changed, 26 insertions(+), 1 deletion(-)
+
+diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
+index 689dd86..51154ae 100644
+--- a/arch/arc/kernel/head.S
++++ b/arch/arc/kernel/head.S
+@@ -49,6 +49,16 @@
+ 1:
+ .endm
+ 
++; Here "patch-dtb" will embed external .dtb
++; Note "patch-dtb" searches for ASCII "OWRTDTB:" string
++; and pastes .dtb right after it, hense the string precedes
++; __image_dtb symbol.
++      .section .owrt, "aw",@progbits
++      .ascii  "OWRTDTB:"
++ENTRY(__image_dtb)
++      .fill   0x4000
++END(__image_dtb)
++
+       .section .init.text, "ax",@progbits
+ 
+ ;----------------------------------------------------------------
+diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
+index c33e77c..96fbfd0 100644
+--- a/arch/arc/kernel/setup.c
++++ b/arch/arc/kernel/setup.c
+@@ -370,6 +370,8 @@ static inline int is_kernel(unsigned long addr)
+       return 0;
+ }
+ 
++extern struct boot_param_header __image_dtb;
++
+ void __init setup_arch(char **cmdline_p)
+ {
+ #ifdef CONFIG_ARC_UBOOT_SUPPORT
+@@ -383,7 +385,7 @@ void __init setup_arch(char **cmdline_p)
+ #endif
+       {
+               /* No, so try the embedded one */
+-              machine_desc = setup_machine_fdt(__dtb_start);
++              machine_desc = setup_machine_fdt(&__image_dtb);
+               if (!machine_desc)
+                       panic("Embedded DT invalid\n");
+ 
+diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
+index dd35bde..f309104 100644
+--- a/arch/arc/kernel/vmlinux.lds.S
++++ b/arch/arc/kernel/vmlinux.lds.S
+@@ -30,6 +30,19 @@ SECTIONS
+ 
+       . = CONFIG_LINUX_LINK_BASE;
+ 
++      /*
++       * In OpenWRT we want to patch built binary embedding .dtb of choice.
++       * This is implemented with "patch-dtb" utility which searches for
++       * "OWRTDTB:" string in first 16k of image and if it is found
++       * copies .dtb right after mentioned string.
++       *
++       * Note: "OWRTDTB:" won't be overwritten with .dtb, .dtb will follow it.
++       */
++      .owrt : {
++              *(.owrt)
++              . = ALIGN(PAGE_SIZE);
++      }
++
+       _int_vec_base_lds = .;
+       .vector : {
+               *(.vector)
+-- 
+2.4.3
+