2017-10-29 18:32:10 +00:00
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From: Alexey Brodkin <abrodkin@synopsys.com>
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Subject: openwrt: arc - add OWRTDTB section
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This change allows OpenWRT to patch resulting kernel binary with
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external .dtb.
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That allows us to re-use exactky the same vmlinux on different boards
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given its ARC core configurations match (at least cache line sizes etc).
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""patch-dtb" searches for ASCII "OWRTDTB:" strign and copies external
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.dtb right after it, keeping the string in place.
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Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
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---
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arch/arc/kernel/head.S | 10 ++++++++++
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arch/arc/kernel/setup.c | 4 +++-
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arch/arc/kernel/vmlinux.lds.S | 13 +++++++++++++
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3 files changed, 26 insertions(+), 1 deletion(-)
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--- a/arch/arc/kernel/head.S
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+++ b/arch/arc/kernel/head.S
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2019-02-27 15:59:49 +00:00
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@@ -59,6 +59,16 @@
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#endif
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2017-10-29 18:32:10 +00:00
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.endm
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+; Here "patch-dtb" will embed external .dtb
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+; Note "patch-dtb" searches for ASCII "OWRTDTB:" string
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+; and pastes .dtb right after it, hense the string precedes
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+; __image_dtb symbol.
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+ .section .owrt, "aw",@progbits
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+ .ascii "OWRTDTB:"
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+ENTRY(__image_dtb)
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+ .fill 0x4000
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+END(__image_dtb)
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+
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.section .init.text, "ax",@progbits
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;----------------------------------------------------------------
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--- a/arch/arc/kernel/setup.c
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+++ b/arch/arc/kernel/setup.c
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2019-05-18 08:59:04 +00:00
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@@ -437,6 +437,8 @@ static inline bool uboot_arg_invalid(uns
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/* We always pass 0 as magic from U-boot */
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#define UBOOT_MAGIC_VALUE 0
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+extern struct boot_param_header __image_dtb;
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+
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void __init handle_uboot_args(void)
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{
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bool use_embedded_dtb = true;
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@@ -477,7 +479,7 @@ ignore_uboot_args:
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2017-10-29 18:32:10 +00:00
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#endif
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2019-02-27 15:59:49 +00:00
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if (use_embedded_dtb) {
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2017-10-29 18:32:10 +00:00
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- machine_desc = setup_machine_fdt(__dtb_start);
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+ machine_desc = setup_machine_fdt(&__image_dtb);
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if (!machine_desc)
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panic("Embedded DT invalid\n");
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2019-02-27 15:59:49 +00:00
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}
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2017-10-29 18:32:10 +00:00
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--- a/arch/arc/kernel/vmlinux.lds.S
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+++ b/arch/arc/kernel/vmlinux.lds.S
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@@ -30,6 +30,19 @@ SECTIONS
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. = CONFIG_LINUX_LINK_BASE;
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+ /*
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+ * In OpenWRT we want to patch built binary embedding .dtb of choice.
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+ * This is implemented with "patch-dtb" utility which searches for
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+ * "OWRTDTB:" string in first 16k of image and if it is found
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+ * copies .dtb right after mentioned string.
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+ *
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+ * Note: "OWRTDTB:" won't be overwritten with .dtb, .dtb will follow it.
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+ */
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+ .owrt : {
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+ *(.owrt)
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+ . = ALIGN(PAGE_SIZE);
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+ }
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+
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_int_vec_base_lds = .;
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.vector : {
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*(.vector)
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