From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:48788 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753630AbeBGNjl (ORCPT ); Wed, 7 Feb 2018 08:39:41 -0500 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Subject: Re: rtlwifi: rtl8821ae: Fix connection lost problem correctly From: Kalle Valo In-Reply-To: <20180205183811.19526-1-Larry.Finger@lwfinger.net> References: <20180205183811.19526-1-Larry.Finger@lwfinger.net> To: Larry Finger Cc: linux-wireless@vger.kernel.org, Larry Finger , Stable Message-Id: <20180207133941.0D9FE60767@smtp.codeaurora.org> (sfid-20180207_143945_595884_29891E11) Date: Wed, 7 Feb 2018 13:39:41 +0000 (UTC) Sender: linux-wireless-owner@vger.kernel.org List-ID: Larry Finger wrote: > 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 commit 40b368af4b75 > ("rtlwifi: Fix alignment issues"); however, this change led to > instability in the connection. To restore stability, this change > was reverted in commit b8b8b16352cd ("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 > , 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: b8b8b16352cd ("rtlwifi: rtl8821ae: Fix connection lost problem") > Cc: Stable # 4.14+ > Fix-suggested-by: Pkshih > Signed-off-by: Larry Finger > Tested-by: James Cameron # x86_64 OLPC NL3 Patch applied to wireless-drivers-next.git, thanks. c713fb071edc rtlwifi: rtl8821ae: Fix connection lost problem correctly -- https://patchwork.kernel.org/patch/10201247/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches