Re: [PATCH v3 3/4] wifi: ath12k: fix source ring-buffer corruption

Baochen Qiang
2025-06-25T01:54:34Z

On 6/17/2025 4:44 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: 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 | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/ath/ath12k/hal.c b/drivers/net/wireless/ath/ath12k/hal.c
> index 726969cfcaec..d8193d9577bb 100644
> --- 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,

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