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| Android - Table of Device Tree |
| ============================== |
| |
| 0) Document revision |
| v1.0 - Initial version (dng) |
| v1.1 - Add v2 format to allow subtype (dng) |
| |
| 1) Android boot image: |
| ---------------------- |
| 1.1) Header: |
| 1) Magic (8B) |
| 2) kernel size (4B) |
| 3) kernel addr (4B) |
| 4) ramdisk size (4B) |
| 5) ramdisk addr (4B) |
| 6) 2ndary size (4B) |
| 7) 2ndary addr (4B) |
| 8) tags addr (4B) |
| 9) page size (4B) |
| 10) unused #1 (4B) (zero in standard Android) |
| 11) unused #2 (4B) (zero in standard Android) |
| 12) product name (16B) |
| 13) kernel cmdline (512B) |
| 14) id (8B) |
| |
| 1.2) Layout: |
| A) header (as above - 1 page) |
| B) kernel (n pages) |
| C) ramdisk (m pages) |
| D) second stage (o pages) |
| |
| 2) QC table of device tree |
| -------------------------- |
| 2.1) Changes: |
| i) use "unused #1, #2" members in existing boot image |
| header to point to new table of device tree |
| (#1 - size of QC table of DT) |
| ii) append table of device tree (described later) |
| after "D) second stage" |
| |
| 2.2) Format: |
| size |
| x +------------------+ |
| | | MAGIC ("QCDT") | 4B |
| | +------------------+ |
| header | VERSION | uint32 (version 3) |
| | +------------------+ |
| | | num of DTBs | uint32 (number of DTB entries) |
| x +------------------+ |
| | | platform id #1 | uint32 (e.g. ID for MSM8974) |
| | +------------------+ |
| | | variant id #1 | uint32 (e.g. ID for CDP, MTP) |
| | +------------------+ |
| | | subtype id #1 | uint32 (e.g. ID for subtype) (QCDT v2) |
| device +------------------+ |
| #1 | soc rev #1 | uint32 (e.g. MSM8974 v2) |
| entry +------------------+ |
| | | pmic0 #1 | uint32 (pmic0-> first smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic1 #1 | uint32 (pmic1-> secondary smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic2 #1 | uint32 (pmic2-> third smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic3 #1 | uint32 (pmic3-> fourth smallest SID of existing pmic) |
| | +------------------+ |
| | | offset #1 | uint32 (byte offset from start/before MAGIC |
| | +------------------+ to DTB entry) |
| | | size #1 | uint32 (size in bytes of DTB blob) |
| x +------------------+ |
| . . |
| . . (repeat) |
| . . |
| |
| x +------------------+ |
| | | platform id #Z | uint32 (e.g. ID for MSM8974) |
| | +------------------+ |
| device | variant id #Z | uint32 (e.g. ID for CDP, MTP) |
| #Z +------------------+ |
| entry | subtype id #Z | uint32 (e.g. ID for subtype) (QCDT v2) |
| (last) +------------------+ |
| | | soc rev #Z | uint32 (e.g. MSM8974 v2) |
| | +------------------+ |
| | | pmic0 #1 | uint32 (pmic0-> first smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic1 #1 | uint32 (pmic1-> secondary smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic2 #1 | uint32 (pmic2-> third smallest SID of existing pmic) |
| | +------------------+ |
| | | pmic3 #1 | uint32 (pmic3-> fourth smallest SID of existing pmic) |
| | +------------------+ |
| | | offset #Z | uint32 (byte offset from start/before MAGIC |
| x +------------------+ to DTB entry) |
| | 0 ("zero") | uint32 (end of list delimiter) |
| +------------------+ to DTB entry) |
| | padding | variable length for next DTB to start on |
| +------------------+ page boundary |
| | DTB #1 | variable (start is page aligned) |
| | | |
| | | |
| +------------------+ |
| | padding | variable length for next DTB to start on |
| +------------------+ page boundary |
| . |
| . |
| . |
| |
| +------------------+ |
| | DTB #Z (last) | variable (start is page aligned) |
| | | |
| | | |
| +------------------+ |
| |
| 3) Operations |
| ------------- |
| 3.1) Build-time: |
| 1) Each DTS per device will add a "qcom,msm-id" entry |
| e.g. for msm8974-sim.dts, add |
| qcom,msm-id = <x y z>; |
| or |
| qcom,msm-id = <x z>; |
| qcom,board-id = <y y'>; |
| or |
| qcom,msm-id = <x z>; |
| qcom,board-id = <y y'>; |
| qcom,pmic-id = <a b c d>; |
| x = ID for msm8974 |
| y = ID for CDP, MTP, etc. |
| y' = ID for subtype (assumed zero if absent) |
| z = ID for soc revision |
| a = pmic0 |
| b = pmic1 |
| c = pmic2 |
| d = pmic3 |
| SBL populates the pmic entries always in ascending order of SID, so |
| pmic0-> SID0, pmic1-> SID1, pmic2-> SID2, pmic3-> SID3. |
| e.g. for qcom,pmic-id = <pmic0 pmic1 pmic2 pmic3> |
| Board X = MSM8994 + PM8994 + PMI8994 (Existing boards [ROW]) |
| Board Y = MSM8994 + PM8994 + PMI8994 + PM8004 (Internal SS board variant) |
| Board Z = MSM8994 + PM8994 + PM8004 (Boards that SS will be making) |
| |
| For all boards X, Y, and Z, PMICs have the following SIDs and REVID SUBTYPEs |
| (i.e. PMIC Model): |
| PM8994 - SID 0 and 1; subtype = 9 |
| PMI8994 - SID 2 and 3; subtype = 10 |
| PM8004 - SID 4 and 5; subtype = 12 |
| |
| LK using SMEM PMIC info(1 as major and 0 as minor version for example): |
| Board X: qcom,pmic-id = <0x0109 0x010A 0x0 0x0>; |
| Board Y: qcom,pmic-id = <0x0109 0x010A 0x010C 0x0>; |
| Board Z: qcom,pmic-id = <0x0109 0x010C 0x0 0x0>; |
| |
| The entry can optionally be an array: |
| qcom,msm-id = <x1 y1 z1>, <x2 y2 z2>, ...; |
| or |
| qcom,msm-id = <x1 z1>, <x2 z2>, ...; |
| qcom,board-id = <y1 y1'>, ...; |
| or |
| qcom,msm-id = <x1 z1>, <x2 z2>, ...; |
| qcom,board-id = <y1 y1'>, ...; |
| qcom,pmic-id = <a1 b1 c1 d1>, ...; |
| Note that qcom,msm-id, qcom,board-id and qcom,pmic-id are not matched pairs. |
| 2) Kernel compile will generate the DTB |
| 3) Android build will run a new tool (dtbTool) |
| a) scan the DTB output directory for all compiled DTB |
| b) decompile the DTB for "qcom,msm-id"/"qcom,board-id"/"qcom,pmic-id" |
| c) generate the QC table of device tree in sorted |
| order (platform, variant, subtype, soc rev, pmic0, pmic1, pmic2, pmic3) |
| d) modified mkbootimg will merge new table of DT |
| |
| 3.2) Run-time: |
| 1) LK bootloader will obtain platform id/variant/subtype/soc rev/major ver/minor ver |
| /pmic0/pmic1/pmic2/pmic3 info either from early bootloaders or via other means |
| 2) LK bootloader will check entries #10 for non-zero |
| value (set to zero for standard boot.img). If the |
| value is non-zero, refer to page section after |
| the "second stage" in the boot.img layout |
| 3) Check QCDT magic |
| 4) Check QCDT version (optional LK to handle multiple |
| QCDT version) |
| 5) LK scans through the QCDT table to look for matching |
| entry. Search order is: |
| 1) msm ID exact match |
| 2) Platform type exact match |
| 3) subtype ID exact match |
| 4) HLOS subtype exact match |
| 5) Pmic0 model ID exact match |
| 6) Pmic1 model ID exact match |
| 7) Pmic2 model ID exact match |
| 8) Pmic3 model ID exact match |
| 9) foundry ID, look for exact match, if not found choose |
| device tree with foundry-id(0x0) |
| 10) select the highest soc rev in QCDT that is |
| equal to or lower than the runtime detected soc rev |
| 11) select the highest major&minor ver in QCDT that is |
| equal to or lower than the runtime detected major ver |
| 12) select the highest pmic0 major&minor in QCDT that is |
| equal to or lower than the runtime detected pmic0 |
| 13) select the highest pmic1 major&minor in QCDT that is |
| equal to or lower than the runtime detected pmic1 |
| 14) select the highest pmic2 major&minor in QCDT that is |
| equal to or lower than the runtime detected pmic2 |
| 15) select the highest pmic3 major&minor in QCDT that is |
| equal to or lower than the runtime detected pmic3 |
| 6) Load the matching DTB blob to the tags addr |
| 7) LK pass the correct DTB to the kernel |