Patch "rtlwifi: rtl8821ae: Fix connection lost problem correctly" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

rtlwifi: rtl8821ae: Fix connection lost problem correctly

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rtlwifi-rtl8821ae-fix-connection-lost-problem-correctly.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Larry Finger <[email protected]>
Date: Mon, 5 Feb 2018 12:38:11 -0600
Subject: rtlwifi: rtl8821ae: Fix connection lost problem correctly

From: Larry Finger <[email protected]>

commit c713fb071edc0efc01a955f65a006b0e1795d2eb upstream.

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 <[email protected]>, 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.

---
 drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c |    5 +++--
 drivers/net/wireless/realtek/rtlwifi/wifi.h         |    1 +
 2 files changed, 4 insertions(+), 2 deletions(-)

@@ -1123,7 +1123,7 @@ static u8 _rtl8821ae_dbi_read(struct rtl
 	}
 	if (0 == tmp) {
 		read_addr = REG_DBI_RDATA + addr % 4;
-		ret = rtl_read_word(rtlpriv, read_addr);
+		ret = rtl_read_byte(rtlpriv, read_addr);
 	}
 	return ret;
 }

@@ -1165,7 +1165,8 @@ static void _rtl8821ae_enable_aspm_back_
 	}
 
 	tmp = _rtl8821ae_dbi_read(rtlpriv, 0x70f);
-	_rtl8821ae_dbi_write(rtlpriv, 0x70f, tmp | BIT(7));
+	_rtl8821ae_dbi_write(rtlpriv, 0x70f, tmp | BIT(7) |
+			     ASPM_L1_LATENCY << 3);
 
 	tmp = _rtl8821ae_dbi_read(rtlpriv, 0x719);
 	_rtl8821ae_dbi_write(rtlpriv, 0x719, tmp | BIT(3) | BIT(4));

@@ -99,6 +99,7 @@
 #define RTL_USB_MAX_RX_COUNT			100
 #define QBSS_LOAD_SIZE				5
 #define MAX_WMMELE_LENGTH			64
+#define ASPM_L1_LATENCY				7
 
 #define TOTAL_CAM_ENTRY				32
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/rtlwifi-rtl8821ae-fix-connection-lost-problem-correctly.patch