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There has been a coding error in rtl8821ae since it was first introduced, namely that an 8-bit register was read using a 16-bit read in _rtl8821ae_dbi_read(). This error was fixed with commit40b368af4b("rtlwifi: Fix alignment issues"); however, this change led to instability in the connection. To restore stability, this change was reverted in commitb8b8b16352("rtlwifi: rtl8821ae: Fix connection lost problem"). Unfortunately, the unaligned access causes machine checks in ARM architecture, and we were finally forced to find the actual cause of the problem on x86 platforms. Following a suggestion from Pkshih <pkshih@realtek.com>, it was found that increasing the ASPM L1 latency from 0 to 7 fixed the instability. This parameter was varied to see if a smaller value would work; however, it appears that 7 is the safest value. A new symbol is defined for this quantity, thus it can be easily changed if necessary. Fixes:b8b8b16352("rtlwifi: rtl8821ae: Fix connection lost problem") Cc: Stable <stable@vger.kernel.org> # 4.14+ Fix-suggested-by: Pkshih <pkshih@realtek.com> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net> Tested-by: James Cameron <quozl@laptop.org> # x86_64 OLPC NL3 Signed-off-by: Kalle Valo <kvalo@codeaurora.org>