Click on each section/summary to see the full content. Done this way since I wrote quite a bit.
What and Why
I recently bought a TD-W9980 (hw rev 1.0) since my TD-W8970 (hw rev 1.2) is apperenlty functinally dead (boot properly but crashes within 5 hours, even with restored original FW, with a complete flash dump). I started toying around with partitions while I was trying to properly configure uboot-envtools. I noticed some "questionable" IMO partitions scheme choices and I am asking here to know if my proposed idea can improve the current situation.
Main HW diffs between W9980, W8980 and W8970
In this thread I'll talk about the TD-W9980 partitions schema, but its valid also for TD-W8980 (same hw with an older case) and TD-W8970 (same hw except for case and 2.4 GHz only wireless chip). The similarity between 9980/8980/8970 can also be seen in the source code, the entry for 9980 does not exist (if you want to compile an image or use one already existing, simply treat it like a 8980) and both 8980's .dts file and 8970's .dts file actually import almost everything from the same .dtsi file (TDW8X90.dtsi).
All different board have an 8MB SPI Flash chip (may not be the same exact chip).
OpenWRT Partition schema
In the shared *.dtsi file (what is used to build the official OpenWRT image for thses routers) the parititon scheme can be found in the &spi section line 238, describing this:
FROM TO SIZE
uboot 0x000000 0x020000 0x020000
firmware 0x020000 0x7C0000 0x7A0000 // where to flash openwrt image
config 0x7C0000 0x7D0000 0x010000 // original fw xml configs
boardconfig 0x7D0000 0x800000 0x030000 // big partition to store the unknown?
boardconfig in the dtsi file is also labelled as ath9k_cal, used at line 112 to tell where the mac addres of the 2.4 GHz wifi chip is (that partition starting offset 0x7D0000 + 0x00F100 = 0x7DF100).
Original FW Parition Schema (what is written in the wiki)
The original firmware partition scheme reported on the owrt wiki is:
FROM TO SIZE
uboot 0x000000 0x020000 0x020000
kernel 0x020000 0x160000 0x140000
rootfs 0x160000 0x7C0000 0x660000
config 0x7C0000 0x7D0000 0x010000
romfile 0x7D0000 0x7E0000 0x010000
rom 0x7E0000 0x7F0000 0x010000
radio 0x7F0000 0x800000 0x010000
Uboot+Lantiq Patches Partition Schema
I was looking to get uboot-envtools working on this router(s), to properly configure it you need to find out the value of some variables (read the uboot-envtools wiki page) and you may need to use the original souce code providded from the router manufacturer (or other external sources, basically not OpenWRT git). I ended up reading the uboot + lantiq patches git, expecially this file (vr9_cfg.h) which describe this partition schema for tons of cases (read the 8 MB SPI Flash chip section specifically, elif block starting at line 598):
FROM TO SIZE
uboot 0x000000 // size unspecified, assumed 0x020000 - until "rootfs"
rootfs 0x020000 // size unspecified
kernel 0x7DFFFF 0x7E0000 0x000001 // what ? maybe is just a "dummy"?
sysconfig 0x7E0000 0x7F0000 0x010000
ubootconfig 0x7F0000 0x7F1000 0x001000 // I was looking for these values
fwdiag 0x7F1000 0x7F2000 0x001000
calibration 0x7F2000 0x7F3000 0x001000
?????? 0x7F3000 0x800000 0x00D000 // space left unpartitioned
Original FW Partition Schema derived from full chip dump
With an external programmer I dumped the content of my router flash chip and tryed to understand how data was "displaced" (looking where large "FF" data section ended), and ended up with this:
FROM TO SIZE
uboot 0x000000 0x020000 0x020000
kernel 0x020000 0x160000 0x140000
rootfs 0x160000 0x7C0000 0x660000
config 0x7C0000 0x7D0000 0x010000 // assumed it ended at 0x7D0000
???? 0x7D0000 0x7DF100 0x00F100 // just empty space FF
wifi mac 0x7DF100 0x7DF200 0x000100 // wifi mac address followed by FF
???? 0x7DF200 0x7E0000 0x000E00 // 8 bytes of something followed by FF
???? 0x7E0000 0x7F0000 0x010000 // 32 bytes of something and FF utill end
ubootcfg??? 0x7F0000 0x7F1100 0x001100 // 6 bytes of something followed by FF
???? 0x7F1100 0x800000 0x00EF00 // 615 bytes of something and FF utill end
Which is a mix of all the 3 partitions schemas explained before.
Proposed Partition Schema + what you think?
So my proposed new partitioning schema is:
FROM TO SIZE
uboot 0x000000 0x020000 0x020000 // unchanged (read only)
firmware 0x020000 0x7D0000 0x7B0000 // just larger -> removed 'config'
boardconfig_1 0x7D0000 0x7F0000 0x020000 // (read only)
ubootconfig 0x7F0000 0x7F1000 0x001000 // (read and write)
boardconfig_2 0x7F1000 0x800000 0x00F000 // (read only)
-
firmwareis 64KiB larger. Theconfigpartition holds the original FW settings, which is quite useless with an OpenWRT fw. It may be argued that 64 KiB is not so much and that is nice to be able to revert to the original fw withouth loosing the original config, buuuut, is always nice to have a bit more space with just 8 MiB of flash chip and before switching to OpenWRT everyone should have already backed up their configuration. -
ubootconfigaccessable read/write without loosing write protection on other sensible region that will remain read only. -
boardconfig_1(was simplyboardconfig) will not change it's starting offset so it can be still labelled asath9k_cal(the wifi mac adress lookup trick). -
boardconfig_1andboardconfig_2are placeholder names, if you have better ideas write them here pls xD I do not know how to name them properly.
Of course this works assuming ubootconfig is actually placed at those adresses (I'll check later, but I can change them if needed), btw regardless that larger firmware partition can still be implemented (by removing the config partition, and 0xFF-ing it maybe?). What do you think?
Modified dtsi file (WIP) Did I wrote this right?
Grab the original dtsi file and change the &spi section. Alwais assuming thath the ubootconfig partitions is really there. Is the format correct? Those two "4" (highlighted by the "#############" lines) are the partition counter and should be changed to "5"?
&spi {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&pins_spi_default>;
m25p80@4 { ###############################
#address-cells = <1>;
#size-cells = <1>;
compatible = "jedec,spi-nor";
reg = <4 0>; ############################
spi-max-frequency = <33250000>;
m25p,fast-read;
partitions {
compatible = "fixed-partitions";
#address-cells = <1>;
#size-cells = <1>;
partition@0 {
reg = <0x0 0x20000>;
label = "u-boot";
read-only;
};
partition@20000 {
reg = <0x20000 0x7b0000>;
label = "firmware";
};
ath9k_cal: partition@7d0000 {
reg = <0x7d0000 0x20000>;
label = "boardconfig_1";
read-only;
};
partition@0x7f0000 {
reg = <0x7f0000 0x1000>;
label = "ubootconfig";
};
partition@0x7f1000 {
reg = <0x7f1000 0xf000>;
label = "boardconfig_2";
read-only;
};
};
};
};
Ty for your help 
sorry for the long post but I like to torture my router and learn new stuffs xD
