[PATCH v2 4/4] wifi: ath12k: fix dest ring-buffer corruption when ring is full

[Johan Hovold <johan+linaro@kernel.org>]

Add the missing memory barriers to make sure that destination ring
descriptors are read before updating the tail pointer (and passing
ownership to the device) to avoid memory corruption on weakly ordered
architectures like aarch64 when the ring is full.

Tested-on: WCN7850 hw2.0 WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
Cc: stable@vger.kernel.org      # 6.3
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
---
 drivers/net/wireless/ath/ath12k/hal.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/hal.c b/drivers/net/wireless/ath/ath12k/hal.c
index 1e2d13cc2d19..4da354e86a75 100644
--- a/drivers/net/wireless/ath/ath12k/hal.c
+++ b/drivers/net/wireless/ath/ath12k/hal.c
@@ -2153,7 +2153,6 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
 {
 	lockdep_assert_held(&srng->lock);
 
-	/* TODO: See if we need a write memory barrier here */
 	if (srng->flags & HAL_SRNG_FLAGS_LMAC_RING) {
 		/* For LMAC rings, ring pointer updates are done through FW and
 		 * hence written to a shared memory location that is read by FW
@@ -2168,7 +2167,11 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
 			WRITE_ONCE(*srng->u.src_ring.hp_addr, srng->u.src_ring.hp);
 		} else {
 			srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
-			*srng->u.dst_ring.tp_addr = srng->u.dst_ring.tp;
+			/* Make sure descriptor is read before updating the
+			 * tail pointer.
+			 */
+			dma_mb();
+			WRITE_ONCE(*srng->u.dst_ring.tp_addr, srng->u.dst_ring.tp);
 		}
 	} else {
 		if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
@@ -2184,6 +2187,10 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
 					   srng->u.src_ring.hp);
 		} else {
 			srng->u.dst_ring.last_hp = *srng->u.dst_ring.hp_addr;
+			/* Make sure descriptor is read before updating the
+			 * tail pointer.
+			 */
+			mb();
 			ath12k_hif_write32(ab,
 					   (unsigned long)srng->u.dst_ring.tp_addr -
 					   (unsigned long)ab->mem,
-- 
2.49.0