ath9k: recover ar9380 chips from rare stuck state

In the experiment with Azimuth ADEPT-n testbed where the APs transmit
power was reduced to 25% and the signal strength was futher attenuated
by 20dB and induced a path loss of ~7dB, the station was reporting
beacon losses and the following issue were observed.

* rx clear is stuck at low for more than 300ms
* dcu chain and complete state is stuck at one of the hang signature

This patch triggers the hang detection logic that recovers the chip
from any of the above conditions. As the issue was originally reported
in ChromeOs with AR9382 chips, this detection logic is enabled only for
AR9380/2 chips.

Cc: Paul Stewart <pstew@google.com>
Reported-by: Gary Morain <gmorain@google.com>
Signed-off-by: Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index 6c69e4e8b1cb..d1345a8a2b15 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -1491,11 +1491,84 @@ static void ath9k_hw_apply_gpio_override(struct ath_hw *ah)
 	}
 }
 
+static bool ath9k_hw_check_dcs(u32 dma_dbg, u32 num_dcu_states,
+			       int *hang_state, int *hang_pos)
+{
+	static u32 dcu_chain_state[] = {5, 6, 9}; /* DCU chain stuck states */
+	u32 chain_state, dcs_pos, i;
+
+	for (dcs_pos = 0; dcs_pos < num_dcu_states; dcs_pos++) {
+		chain_state = (dma_dbg >> (5 * dcs_pos)) & 0x1f;
+		for (i = 0; i < 3; i++) {
+			if (chain_state == dcu_chain_state[i]) {
+				*hang_state = chain_state;
+				*hang_pos = dcs_pos;
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
+#define DCU_COMPLETE_STATE        1
+#define DCU_COMPLETE_STATE_MASK 0x3
+#define NUM_STATUS_READS         50
+static bool ath9k_hw_detect_mac_hang(struct ath_hw *ah)
+{
+	u32 chain_state, comp_state, dcs_reg = AR_DMADBG_4;
+	u32 i, hang_pos, hang_state, num_state = 6;
+
+	comp_state = REG_READ(ah, AR_DMADBG_6);
+
+	if ((comp_state & DCU_COMPLETE_STATE_MASK) != DCU_COMPLETE_STATE) {
+		ath_dbg(ath9k_hw_common(ah), RESET,
+			"MAC Hang signature not found at DCU complete\n");
+		return false;
+	}
+
+	chain_state = REG_READ(ah, dcs_reg);
+	if (ath9k_hw_check_dcs(chain_state, num_state, &hang_state, &hang_pos))
+		goto hang_check_iter;
+
+	dcs_reg = AR_DMADBG_5;
+	num_state = 4;
+	chain_state = REG_READ(ah, dcs_reg);
+	if (ath9k_hw_check_dcs(chain_state, num_state, &hang_state, &hang_pos))
+		goto hang_check_iter;
+
+	ath_dbg(ath9k_hw_common(ah), RESET,
+		"MAC Hang signature 1 not found\n");
+	return false;
+
+hang_check_iter:
+	ath_dbg(ath9k_hw_common(ah), RESET,
+		"DCU registers: chain %08x complete %08x Hang: state %d pos %d\n",
+		chain_state, comp_state, hang_state, hang_pos);
+
+	for (i = 0; i < NUM_STATUS_READS; i++) {
+		chain_state = REG_READ(ah, dcs_reg);
+		chain_state = (chain_state >> (5 * hang_pos)) & 0x1f;
+		comp_state = REG_READ(ah, AR_DMADBG_6);
+
+		if (((comp_state & DCU_COMPLETE_STATE_MASK) !=
+					DCU_COMPLETE_STATE) ||
+		    (chain_state != hang_state))
+			return false;
+	}
+
+	ath_dbg(ath9k_hw_common(ah), RESET, "MAC Hang signature 1 found\n");
+
+	return true;
+}
+
 bool ath9k_hw_check_alive(struct ath_hw *ah)
 {
 	int count = 50;
 	u32 reg;
 
+	if (AR_SREV_9300(ah))
+		return !ath9k_hw_detect_mac_hang(ah);
+
 	if (AR_SREV_9285_12_OR_LATER(ah))
 		return true;