target/linux/brcm63xx/patches-3.18/366-MIPS-add-support-for-vmlinux.bin-appended-DTB.patch

   1 From 318c1fce4aeef298cbb6153416c499c94ad7cda0 Mon Sep 17 00:00:00 2001
   2 From: Jonas Gorski <jogo@openwrt.org>
   3 Date: Tue, 24 Jun 2014 10:53:15 +0200
   4 Subject: [PATCH RFC v3] MIPS: add support for vmlinux.bin appended DTB
   5
   6 Add support for populating initial_boot_params through a dtb
   7 blob appended to raw vmlinux.bin.
   8
   9 Signed-off-by: Jonas Gorski <jogo@openwrt.org>
  10 ---
  11 Changes RFC v2 -> v3
  12
  13 * fixed !smp kernels (TODO: move it to its own patch
  14
  15 Changes RFC v1 -> v2
  16
  17 * changed all occurences of vmlinux to vmlinux.bin
  18 * clarified this applies to the raw vmlinux.bin without decompressor
  19 * s/initial_device_params/initial_boot_params/
  20
  21 Initial comments by me still valid:
  22
  23 Mostly adapted from how ARM is doing it.
  24
  25 Sent as an RFC PATCH because I am not sure if this is the right way to
  26 it, and whether storing the pointer in initial_boot_params is a good
  27 idea, or a new variable should be introduced.
  28
  29 The reasoning for initial_boot_params is that there is no common
  30 MIPS interface yet, so the next best thing was using that. This also
  31 has the advantage of keeping the original fw_args intact.
  32
  33 This patch works for me on bcm63xx, where the bootloader expects
  34 an lzma compressed kernel, so I didn't want to double compress using
  35 the in-kernel compressed kernel support.
  36
  37 Completely untested on anything except MIPS32 / big endian.
  38
  39  arch/mips/Kconfig              | 18 ++++++++++++++++++
  40  arch/mips/kernel/head.S        | 19 +++++++++++++++++++
  41  arch/mips/kernel/vmlinux.lds.S |  7 +++++++
  42  3 files changed, 43 insertions(+)
  43
  44 --- a/arch/mips/Kconfig
  45 +++ b/arch/mips/Kconfig
  46 @@ -2645,6 +2645,24 @@ config RAPIDIO
  47
  48  source "drivers/rapidio/Kconfig"
  49
  50 +config MIPS_APPENDED_DTB
  51 +       bool "Use appended device tree blob to vmlinux.bin (EXPERIMENTAL)"
  52 +       depends on OF
  53 +       help
  54 +         With this option, the boot code will look for a device tree binary
  55 +         DTB) appended to raw vmlinux.bin (without decompressor).
  56 +         (e.g. cat vmlinux.bin <filename>.dtb > vmlinux_w_dtb).
  57 +
  58 +         This is meant as a backward compatibility convenience for those
  59 +         systems with a bootloader that can't be upgraded to accommodate
  60 +         the documented boot protocol using a device tree.
  61 +
  62 +         Beware that there is very little in terms of protection against
  63 +         this option being confused by leftover garbage in memory that might
  64 +         look like a DTB header after a reboot if no actual DTB is appended
  65 +         to vmlinux.bin.  Do not leave this option active in a production kernel
  66 +         if you don't intend to always append a DTB.
  67 +
  68  endmenu
  69
  70  menu "Executable file formats"
  71 --- a/arch/mips/kernel/head.S
  72 +++ b/arch/mips/kernel/head.S
  73 @@ -100,6 +100,22 @@ NESTED(kernel_entry, 16, sp)                       # kernel
  74         jr      t0
  75  0:
  76
  77 +#ifdef CONFIG_MIPS_APPENDED_DTB
  78 +       PTR_LA          t0, __appended_dtb
  79 +       PTR_LI          t3, 0
  80 +
  81 +#ifdef CONFIG_CPU_BIG_ENDIAN
  82 +       PTR_LI          t1, 0xd00dfeed
  83 +#else
  84 +       PTR_LI          t1, 0xedfe0dd0
  85 +#endif
  86 +       LONG_L          t2, (t0)
  87 +       bne             t1, t2, not_found
  88 +
  89 +       PTR_LA          t3, __appended_dtb
  90 +
  91 +not_found:
  92 +#endif
  93         PTR_LA          t0, __bss_start         # clear .bss
  94         LONG_S          zero, (t0)
  95         PTR_LA          t1, __bss_stop - LONGSIZE
  96 @@ -113,6 +129,10 @@ NESTED(kernel_entry, 16, sp)                       # kernel
  97         LONG_S          a2, fw_arg2
  98         LONG_S          a3, fw_arg3
  99
 100 +#ifdef CONFIG_MIPS_APPENDED_DTB
 101 +       LONG_S          t3, initial_boot_params
 102 +#endif
 103 +
 104         MTC0            zero, CP0_CONTEXT       # clear context register
 105         PTR_LA          $28, init_thread_union
 106         /* Set the SP after an empty pt_regs.  */
 107 --- a/arch/mips/kernel/vmlinux.lds.S
 108 +++ b/arch/mips/kernel/vmlinux.lds.S
 109 @@ -125,8 +125,14 @@ SECTIONS
 110         .exit.data : {
 111                 EXIT_DATA
 112         }
 113 -
 114 +#ifdef CONFIG_SMP
 115         PERCPU_SECTION(1 << CONFIG_MIPS_L1_CACHE_SHIFT)
 116 +#endif
 117 +#ifdef CONFIG_MIPS_APPENDED_DTB
 118 +       __appended_dtb = .;
 119 +       /* leave space for appended DTB */
 120 +       . = . + 0x100000;
 121 +#endif
 122         /*
 123          * Align to 64K in attempt to eliminate holes before the
 124          * .bss..swapper_pg_dir section at the start of .bss.  This