I asked this question back in January [here] but got no response so I will try again here.
Later firmware versions have since been been released for the two that I refer to but the question remains the same; how do they differ? (http://lists.infradead.org/pipermail/ath10k/2019-January/012661.html)
Hi,
There are two current builds of QCA988X/hw2.0 firmware: -
a) firmware-5.bin_10.2.4-1.0 -> latest -> firmware-5.bin_10.2.4-1.0-00043
b) firmware-5.bin_10.2.4.70 -> latest -> firmware-5.bin_10.2.4.70.69
The site https://wireless.wiki.kernel.org/en/users/drivers/ath10k/firmware
indicates that both of these are suitable for Kernel version 4 and
they both work in my ar71xx-generic-archer-c7-v2 router with OpenWrt
18.06.1 which was itself originally packaged with 10.2.4-1.0-00033
Both firmware have the same options: -
firmware ver 10.2.4.70.69 api 5 features
no-p2p,raw-mode,mfp,allows-mesh-bcast crc32 edfb196a
firmware ver 10.2.4-1.0-00043 api 5 features
no-p2p,raw-mode,mfp,allows-mesh-bcast crc32 ed0aafd8
If you’re not using 802.11s mesh, both the “classic” and “CT” versions work well for me on my Archer C7v2 units.
The older chips in the Archer C7v2 only have 802.11s support under the “classic” version. They are a now-outdated hardware class that CT is no longer spending a great amount of development effort on, from what I understand.
I call the driver/firmware packages that OpenWrt suffixes with -ct “CT” and those without a suffix “classic”. The CT drivers are documented in detail on the Candela Technology website. Recently OpenWrt switched to the CT drivers as the default. Both are available as packages and in the build system.
It's at least the Qualcomm Atheros QCA9880-BR4A, used by the Archer C7v2. and probably some other, similar-generation chips. I believe they're referred to as "Wave-1" chips.
Surprisingly, the Netgear R7500 comes up in the list of devices using this older chip, even though showing as available in 2019.
Interesting subject. I have exactly the same questions. I am experimenting and comparing for some time now the different versions and flavours in my builds on same wlan hw qca988x . I compared firmware-5.bin_10.2.4-1.0-00041 versus firmware-5.bin_10.2.4.70.69 and could not find any difference (except different name-file lenght-sha256sum). Checking iw phyx info as well gives no clue. All the mentioned qca versions run stable. I understand there are nda requirements but at least minimal information such as bug fixes and difference etc would be appreciated . Btw latest versions are now firmware-5.bin_10.2.4-1.0-00045 and firmware-5.bin_10.2.4.70.70 (as per https://github.com/kvalo/ath10k-firmware/tree/master/QCA988X/hw2.0), running stable as well.
I was referring to the qca, aka "classic", firmware. But indeed the Candela Tech, aka "CT", fw development looks very promising, impressed to see the number of backported features. At least they do describe each release very decently . Unfortunately there still is a, at least one afaik, nasty bug causing occasional fw crash. Fortunately each crash, in my case, recovered automatically and I am currently trying to reproduce with high certainty in order to be able to deliver a decent quality bug report.
Thanks for all of the answers but if anything I am now even more confused because there appears to be another source of "CT" firmware versions based on the original Qualcom (http://www.candelatech.com/ath10k-10.1.php)
How do these relate to the versions in my original post?
There are two current builds of QCA988X/hw2.0 firmware: -
a) firmware-5.bin_10.2.4-1.0 -> latest -> firmware-5.bin_10.2.4-1.0-00045
b) firmware-5.bin_10.2.4.70 -> latest -> firmware-5.bin_10.2.4.70.70
The version packaged with OpenWRT appears to be from the 10.2.4-1.0 branch (37 in the last patch). Is the -1.0 branch just another naming convention for the ct versions from Candela?
The "classic" is upstream, the CT is an alternate, that is selected by default by OpenWrt. Versions can be found in the various sources (there are both driver and firmware for each). There are also several variants of the CT firmware. Check the various Makefile for details of specific versions and where they come from (such as package/firmware/ath10k-firmware/Makefile for the firmware options)
. Btw latest versions are now firmware-5.bin_10.2.4-1.0-00045 and firmware-5.bin_10.2.4.70.70 (as per 
. Unfortunately there still is a, at least one afaik, nasty bug causing occasional fw crash. Fortunately each crash, in my case, recovered automatically and I am currently trying to reproduce with high certainty in order to be able to deliver a decent quality bug report.