Comment 18 for bug 1618267

Summary; my own rtl8821ae frequent connection lost problem was fixed by upstream patch b8b8b16352cd ("rtlwifi: rtl8821ae: Fix connection lost problem") merged for 4.14-rc4.

I've recently fixed a problem very much like the problems reported in this bug; and during my tests I saw the cycling ping times, the delay unloading the module, and the no buffer space, all of which suggested a firmware hang in the wireless device.

My main problem was that connection was lost shortly after it was made, and especially if there was a burst of download data. Workaround was to turn wireless off then on again, or reboot.

What I did was

(a) test several ubuntu kernels to find which ones were affected,

(b) using git bisect, tested several custom kernels, and proved my problem began with a single commit 40b368af4b75 ("rtlwifi: Fix alignment issues"),

(c) worked with upstream to determine a likely cause; the commit wasn't widely tested,

(d) proved through testing that the BIOS can have an effect; because the rtl8821ae driver does not reset the card, but inherits the card in whatever state the BIOS left it. This can randomise problem reports.

(e) proved that a power down and reboot can have a different effect to a warm reboot; some of the wireless card device registers are unchanged on warm reboot. This can randomise problem reports.

Hope that helps.