linux-kernel - Re: [PATCH] wifi: ath12k: extend dma mask to 36 bits

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Message-ID: <50395ba6-8954-66fc-9d94-a58d22606a85@oss.qualcomm.com>
Date: Wed, 26 Mar 2025 09:59:30 +0530
From: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@....qualcomm.com>
To: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>, ath12k@...ts.infradead.org
Cc: Jeff Johnson <jjohnson@...nel.org>,
        Stephan Gerhold <stephan.gerhold@...aro.org>,
        linux-kernel@...r.kernel.org, Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH] wifi: ath12k: extend dma mask to 36 bits

Adding original to and cc list back.

When replying please keep all the email addresses as in the original mail.

On 3/25/2025 12:34 PM, Raj Kumar Bhagat wrote:
> On 3/21/2025 9:53 PM, Johan Hovold wrote:
>> Extend the DMA mask to 36 bits to avoid using bounce buffers on machines
>> without an iommu (under OS control) similar to what was done for ath11k
>> in commit dbd73acb22d8 ("wifi: ath11k: enable 36 bit mask for stream
>> DMA").
>>
>> This specifically avoids using bounce buffers on Qualcomm Snapdragon X
>> Elite machines like the Lenovo ThinkPad T14s when running at EL1.
>>
>> Note that the mask could possibly be extended further but unresolved DMA
>> issues with 64 GiB X Elite machines currently prevents that from being
>> tested.
>>
>> Also note that the driver is limited to 32 bits for coherent
>> allocations and that there is no need to check for errors when setting
>> masks larger than 32 bits.
>>
>> Tested-on: WCN7850 hw2.0 WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
> 
> Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1
> 
> Tested-by: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>
> 
> Validated iperf traffic on QCN9274 with FW version -
> WLAN.WBE.1.4.1-00199-QCAHKSWPL_SILICONZ-1
>