[PATCH v2 4/5] wifi: ath11k: fix source ring-buffer corruption

[Baochen Qiang]

On 6/4/2025 10:34 PM, Johan Hovold wrote:
> 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: WCN6855 hw2.1 WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.41
> 
> Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
> Cc: stable at vger.kernel.org      # 5.6
> Signed-off-by: Johan Hovold <johan+linaro at kernel.org>
> ---
>  drivers/net/wireless/ath/ath11k/hal.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
> index b1f5a927dddd..927ed2bc3fbf 100644
> --- a/drivers/net/wireless/ath/ath11k/hal.c
> +++ b/drivers/net/wireless/ath/ath11k/hal.c
> @@ -862,7 +862,11 @@ void ath11k_hal_srng_access_end(struct ath11k_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;
> @@ -871,6 +875,10 @@ void ath11k_hal_srng_access_end(struct ath11k_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.
> +			 */
>  			ath11k_hif_write32(ab,
>  					   (unsigned long)srng->u.src_ring.hp_addr -
>  					   (unsigned long)ab->mem,

Reviewed-by: Baochen Qiang <quic_bqiang at quicinc.com>