wifi: ath12k: fix source ring-buffer corruption

Add the missing memory barrier to make sure that LMAC source ring
descriptors are written before updating the head pointer to avoid
passing stale data to the firmware on weakly ordered architectures like
aarch64.

Note that non-LMAC rings use MMIO write accessors which have the
required write memory barrier.

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>
Reviewed-by: Baochen Qiang <quic_bqiang@quicinc.com>
Link: https://patch.msgid.link/20250617084402.14475-4-johan+linaro@kernel.org
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>

diff --git a/drivers/net/wireless/ath/ath12k/hal.c b/drivers/net/wireless/ath/ath12k/hal.c
index 726969cfcaec2a8646feb2b1041abe3966554db0..d8193d9577bb16e614e273bad537b5bb84b251bc 100644 (file)
--- a/drivers/net/wireless/ath/ath12k/hal.c
+++ b/drivers/net/wireless/ath/ath12k/hal.c
@@ -2178,7 +2178,11 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
                if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
                        srng->u.src_ring.last_tp =
                                *(volatile u32 *)srng->u.src_ring.tp_addr;
-                       *srng->u.src_ring.hp_addr = srng->u.src_ring.hp;
+                       /* Make sure descriptor is written before updating the
+                        * head pointer.
+                        */
+                       dma_wmb();
+                       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;
@@ -2187,6 +2191,10 @@ void ath12k_hal_srng_access_end(struct ath12k_base *ab, struct hal_srng *srng)
                if (srng->ring_dir == HAL_SRNG_DIR_SRC) {
                        srng->u.src_ring.last_tp =
                                *(volatile u32 *)srng->u.src_ring.tp_addr;
+                       /* Assume implementation use an MMIO write accessor
+                        * which has the required wmb() so that the descriptor
+                        * is written before the updating the head pointer.
+                        */
                        ath12k_hif_write32(ab,
                                           (unsigned long)srng->u.src_ring.hp_addr -
                                           (unsigned long)ab->mem,