target/linux/arc770/patches-4.3/0002-openwrt-arc-add-OWRTDTB-section.patch

   1 From 142abc9f7b8860638e39cf3850cf7ba328c26b42 Mon Sep 17 00:00:00 2001
   2 From: Alexey Brodkin <abrodkin@synopsys.com>
   3 Date: Sat, 31 Oct 2015 15:58:20 +0300
   4 Subject: [PATCH] openwrt: arc - add OWRTDTB section
   5
   6 This change allows OpenWRT to patch resulting kernel binary with
   7 external .dtb.
   8
   9 That allows us to re-use exactky the same vmlinux on different boards
  10 given its ARC core configurations match (at least cache line sizes etc).
  11
  12 ""patch-dtb" searches for ASCII "OWRTDTB:" strign and copies external
  13 .dtb right after it, keeping the string in place.
  14
  15 Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
  16 ---
  17  arch/arc/kernel/head.S        | 10 ++++++++++
  18  arch/arc/kernel/setup.c       |  4 +++-
  19  arch/arc/kernel/vmlinux.lds.S | 13 +++++++++++++
  20  3 files changed, 26 insertions(+), 1 deletion(-)
  21
  22 --- a/arch/arc/kernel/head.S
  23 +++ b/arch/arc/kernel/head.S
  24 @@ -49,6 +49,16 @@
  25  1:
  26  .endm
  27
  28 +; Here "patch-dtb" will embed external .dtb
  29 +; Note "patch-dtb" searches for ASCII "OWRTDTB:" string
  30 +; and pastes .dtb right after it, hense the string precedes
  31 +; __image_dtb symbol.
  32 +       .section .owrt, "aw",@progbits
  33 +       .ascii  "OWRTDTB:"
  34 +ENTRY(__image_dtb)
  35 +       .fill   0x4000
  36 +END(__image_dtb)
  37 +
  38         .section .init.text, "ax",@progbits
  39         .type stext, @function
  40         .globl stext
  41 --- a/arch/arc/kernel/setup.c
  42 +++ b/arch/arc/kernel/setup.c
  43 @@ -374,6 +374,8 @@ static inline int is_kernel(unsigned lon
  44         return 0;
  45  }
  46
  47 +extern struct boot_param_header __image_dtb;
  48 +
  49  void __init setup_arch(char **cmdline_p)
  50  {
  51  #ifdef CONFIG_ARC_UBOOT_SUPPORT
  52 @@ -387,7 +389,7 @@ void __init setup_arch(char **cmdline_p)
  53  #endif
  54         {
  55                 /* No, so try the embedded one */
  56 -               machine_desc = setup_machine_fdt(__dtb_start);
  57 +               machine_desc = setup_machine_fdt(&__image_dtb);
  58                 if (!machine_desc)
  59                         panic("Embedded DT invalid\n");
  60
  61 --- a/arch/arc/kernel/vmlinux.lds.S
  62 +++ b/arch/arc/kernel/vmlinux.lds.S
  63 @@ -30,6 +30,19 @@ SECTIONS
  64
  65         . = CONFIG_LINUX_LINK_BASE;
  66
  67 +       /*
  68 +        * In OpenWRT we want to patch built binary embedding .dtb of choice.
  69 +        * This is implemented with "patch-dtb" utility which searches for
  70 +        * "OWRTDTB:" string in first 16k of image and if it is found
  71 +        * copies .dtb right after mentioned string.
  72 +        *
  73 +        * Note: "OWRTDTB:" won't be overwritten with .dtb, .dtb will follow it.
  74 +        */
  75 +       .owrt : {
  76 +               *(.owrt)
  77 +               . = ALIGN(PAGE_SIZE);
  78 +       }
  79 +
  80         _int_vec_base_lds = .;
  81         .vector : {
  82                 *(.vector)