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. Fixes: b8b8b16352cd ("rtlwifi: rtl8821ae: Fix connection lost problem") Cc: Stable <[email protected]> # 4.14+ Fix-suggested-by: Pkshih <[email protected]> Signed-off-by: Larry Finger <[email protected]> --- Kalle, This patch should be submitted to 4.16. Larry --- drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c | 5 +++-- drivers/net/wireless/realtek/rtlwifi/wifi.h | 1 + 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c index f20e77b4bb65..317c1b3101da 100644 --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c @@ -1123,7 +1123,7 @@ static u8 _rtl8821ae_dbi_read(struct rtl_priv *rtlpriv, u16 addr) } 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_door(struct ieee80211_hw *hw) } 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)); diff --git a/drivers/net/wireless/realtek/rtlwifi/wifi.h b/drivers/net/wireless/realtek/rtlwifi/wifi.h index 1c9ed28b42da..4f48b934ec01 100644 --- a/drivers/net/wireless/realtek/rtlwifi/wifi.h +++ b/drivers/net/wireless/realtek/rtlwifi/wifi.h @@ -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 -- 2.16.1
