[PATCH] wifi: ath12k: fix DMA unmap warning on NULL DMA address

[Jeff Johnson]

On 8/29/2023 7:11 PM, Baochen Qiang wrote:
> In ath12k_dp_tx(), if we reach fail_dma_unmap due to some errors,
> current code does DMA unmap unconditionally on skb_cb->paddr_ext_desc.
> However, skb_cb->paddr_ext_desc may be NULL and thus we get below
> warning:
> 
> kernel: [ 8887.076212] WARNING: CPU: 3 PID: 0 at drivers/iommu/dma-iommu.c:1077 iommu_dma_unmap_page+0x79/0x90
> 
> Fix it by checking skb_cb->paddr_ext_desc before unmap it.
> 
> Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4
> 
> Fixes: d889913205cf ("wifi: ath12k: driver for Qualcomm Wi-Fi 7 devices")
> Signed-off-by: Baochen Qiang <quic_bqiang at quicinc.com>

Acked-by: Jeff Johnson <quic_jjohnson at quicinc.com>

> ---
>   drivers/net/wireless/ath/ath12k/dp_tx.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath12k/dp_tx.c b/drivers/net/wireless/ath/ath12k/dp_tx.c
> index 8874c815d7fa..c0ae2fd443cc 100644
> --- a/drivers/net/wireless/ath/ath12k/dp_tx.c
> +++ b/drivers/net/wireless/ath/ath12k/dp_tx.c
> @@ -330,8 +330,10 @@ int ath12k_dp_tx(struct ath12k *ar, struct ath12k_vif *arvif,
>   
>   fail_unmap_dma:
>   	dma_unmap_single(ab->dev, ti.paddr, ti.data_len, DMA_TO_DEVICE);
> -	dma_unmap_single(ab->dev, skb_cb->paddr_ext_desc,
> -			 sizeof(struct hal_tx_msdu_ext_desc), DMA_TO_DEVICE);
> +	if (skb_cb->paddr_ext_desc)
> +		dma_unmap_single(ab->dev, skb_cb->paddr_ext_desc,
> +				 sizeof(struct hal_tx_msdu_ext_desc),
> +				 DMA_TO_DEVICE);
>   
>   fail_remove_tx_buf:
>   	ath12k_dp_tx_release_txbuf(dp, tx_desc, pool_id);
> 
> base-commit: a62b0aeb556839fb6abb9835874443b08fe95598