c713fb071e
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
<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: b8b8b16352cd ("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>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.