Re: [PATCH v3] wifi: ath11k: Fix MHI target memory reuse logic

[Baochen Qiang <quic_bqiang@quicinc.com>]

On 4/25/2025 1:51 PM, Muhammad Usama Anjum wrote:
> Firmware requests 2 segments at first. The first segment is of 6799360
> whose allocation fails due to dma remapping not available. The success
> is returned to firmware. Then firmware asks for 22 smaller segments
> instead of 2 big ones. Those get allocated successfully. At suspend/
> hibernation time, these segments aren't freed as they will be reused
> by firmware after resuming.
> 
> After resuming, the firmware asks for the 2 segments again with the
> first segment of 6799360 size. Since chunk->vaddr is not NULL, the
> type and size are compared with the previous type and size to know if
> it can be reused or not. Unfortunately, it is detected that it cannot
> be reused and this first smaller segment is freed. Then we continue to
> allocate 6799360 size memory which fails and ath11k_qmi_free_target_mem_chunk()
> is called which frees the second smaller segment as well. Later success
> is returned to firmware which asks for 22 smaller segments again. But
> as we had freed 2 segments already, we'll allocate the first 2 new
> smaller segments again and reuse the remaining 20. Hence 20 small
> segments are being reused instead of 22.
> 
> Add skip logic when vaddr is set, but size/type don't match. Use the
> same skip and success logic as used when dma_alloc_coherent() fails


till here it is good.

but from below

> without freeing the memory area. The following error are being fixed at
> resume:
> 
> 	kernel: ath11k_pci 0000:03:00.0: failed to allocate dma memory for qmi (524288 B type 1)
> 	ath11k_pci 0000:03:00.0: failed to allocate qmi target memory: -22
> 
> Those failures aren't because of the bigger chunk allocation failure as
> they are skipped. Rather these failures are because of smaller chunk
> allocation failures. This patch fixes freeing and allocation of 2 smaller
> chunks.

to here not good to me, as it gives me the impression that you are fixing a kernel
allocation failure.

How about rephrase like:

By skipping, the possibility of resume failure due to kernel failing to allocate memory
for QMI can be avoided.

> 
> Tested-on: WCN6855 WLAN.HSP.1.1-03926.13-QCAHSPSWPL_V2_SILICONZ_CE-2.52297.6
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
> ---
> Changes since v1:
> - Update description
> 
> Changes since v2:
> - Update description
> ---
>  drivers/net/wireless/ath/ath11k/qmi.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/qmi.c b/drivers/net/wireless/ath/ath11k/qmi.c
> index 47b9d4126d3a9..2782f4723e413 100644
> --- a/drivers/net/wireless/ath/ath11k/qmi.c
> +++ b/drivers/net/wireless/ath/ath11k/qmi.c
> @@ -1993,6 +1993,15 @@ static int ath11k_qmi_alloc_target_mem_chunk(struct ath11k_base *ab)
>  			    chunk->prev_size == chunk->size)
>  				continue;
>  
> +			if (ab->qmi.mem_seg_count <= ATH11K_QMI_FW_MEM_REQ_SEGMENT_CNT) {
> +				ath11k_dbg(ab, ATH11K_DBG_QMI,
> +					   "size/type mismatch (current %d %u) (prev %d %u), try later with small size\n",
> +					    chunk->size, chunk->type,
> +					    chunk->prev_size, chunk->prev_type);
> +				ab->qmi.target_mem_delayed = true;
> +				return 0;
> +			}
> +
>  			/* cannot reuse the existing chunk */
>  			dma_free_coherent(ab->dev, chunk->prev_size,
>  					  chunk->vaddr, chunk->paddr);