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@xxxxxxxxxxxxxxx # 5.6
> Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> ---
> 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@xxxxxxxxxxx>
