add dtbtool.txt
xiaolu
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f264a09b19
commit
7efc76da24
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Refer to device/*/dtbtool.txt
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---------------------------------------------------------------------
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Copyright (c) 2012, The Linux Foundation. All rights reserved.
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Redistribution and use in source form and compiled forms (SGML, HTML,
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PDF, PostScript, RTF and so forth) with or without modification, are
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permitted provided that the following conditions are met:
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Redistributions in source form must retain the above copyright
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notice, this list of conditions and the following disclaimer as the
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first lines of this file unmodified.
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Redistributions in compiled form (transformed to other DTDs,
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converted to PDF, PostScript, RTF and other formats) must reproduce
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the above copyright notice, this list of conditions and the following
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disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS DOCUMENTATION IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE AND
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NON-INFRINGEMENT ARE DISCLAIMED. IN NO EVENT SHALL THE FREEBSD
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DOCUMENTATION PROJECT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS DOCUMENTATION, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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DAMAGE.
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Android - Table of Device Tree
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==============================
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0) Document revision
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v1.0 - Initial version (dng)
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1) Android boot image:
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----------------------
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1.1) Header:
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1) Magic (8B)
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2) kernel size (4B)
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3) kernel addr (4B)
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4) ramdisk size (4B)
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5) ramdisk addr (4B)
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6) 2ndary size (4B)
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7) 2ndary addr (4B)
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8) tags addr (4B)
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9) page size (4B)
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10) unused #1 (4B) (zero in standard Android)
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11) unused #2 (4B) (zero in standard Android)
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12) product name (16B)
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13) kernel cmdline (512B)
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14) id (8B)
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1.2) Layout:
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A) header (as above - 1 page)
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B) kernel (n pages)
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C) ramdisk (m pages)
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D) second stage (o pages)
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2) QC table of device tree
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--------------------------
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2.1) Changes:
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i) use "unused #1, #2" members in existing boot image
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header to point to new table of device tree
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(#1 - size of QC table of DT)
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ii) append table of device tree (described later)
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after "D) second stage"
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2.2) Format:
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size
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x +------------------+
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| | MAGIC ("QCDT") | 4B
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| +------------------+
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header | VERSION | uint32 (initial version 1)
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| +------------------+
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| | num of DTBs | uint32 (number of DTB entries)
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x +------------------+
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| | platform id #1 | uint32 (e.g. ID for MSM8974)
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| +------------------+
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| | variant id #1 | uint32 (e.g. ID for CDP, MTP)
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device +------------------+
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#1 | soc rev #1 | uint32 (e.g. MSM8974 v2)
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entry +------------------+
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| | offset #1 | uint32 (byte offset from start/before MAGIC
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| +------------------+ to DTB entry)
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| | size #1 | uint32 (size in bytes of DTB blob)
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x +------------------+
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. .
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. . (repeat)
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. .
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x +------------------+
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| | platform id #Z | uint32 (e.g. ID for MSM8974)
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| +------------------+
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device | variant id #Z | uint32 (e.g. ID for CDP, MTP)
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#Z +------------------+
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entry | soc rev #Z | uint32 (e.g. MSM8974 v2)
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(last) +------------------+
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| | offset #Z | uint32 (byte offset from start/before MAGIC
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x +------------------+ to DTB entry)
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| 0 ("zero") | uint32 (end of list delimiter)
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+------------------+ to DTB entry)
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| padding | variable length for next DTB to start on
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+------------------+ page boundary
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| DTB #1 | variable (start is page aligned)
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| |
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| |
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+------------------+
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| padding | variable length for next DTB to start on
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+------------------+ page boundary
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.
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.
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.
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+------------------+
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| DTB #Z (last) | variable (start is page aligned)
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| |
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| |
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+------------------+
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3) Operations
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-------------
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3.1) Build-time:
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1) Each DTS per device will add a "qcom,msm-id" triplet
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e.g. for msm8974-sim.dts, add
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qcom,msm-id = <x y z>;
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x = ID for msm8974
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y = ID for CDP, MTP, etc.
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z = ID for soc revision
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The triplet can optionally be an array of triplets:
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qcom,msm-id = <x1, y1, z1>, <x2, y2, z2>, ...;
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2) Kernel compile will generate the DTB
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3) Android build will run a new tool (dtbTool)
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a) scan the DTB output directory for all compiled DTB
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b) decompile the DTB for "qcom,msm-id"
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c) generate the QC table of device tree in sorted
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order (platform, variant, soc rev)
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d) modified mkbootimg will merge new table of DT
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3.2) Run-time:
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1) LK bootloader will obtain MSM id/variant/soc rev info
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either from early bootloaders or via other means
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2) LK bootloader will check entries #10 for non-zero
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value (set to zero for standard boot.img). If the
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value is non-zero, refer to page section after
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the "second stage" in the boot.img layout
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3) Check QCDT magic
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4) Check QCDT version (optional LK to handle multiple
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QCDT version)
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5) LK scans through the QCDT table to look for matching
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entry. Search order is:
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1) platform ID exact match
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2) variant ID exact match
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3) select the highest soc rev in QCDT that is
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equal to or lower than the runtime detected soc rev
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6) Load the matching DTB blob to the tags addr
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7) LK pass the correct DTB to the kernel
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