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

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Message-ID: <Z-EjaQ70mtQwQsgs@hovoldconsulting.com>
Date: Mon, 24 Mar 2025 10:18:33 +0100
From: Johan Hovold <johan@...nel.org>
To: Baochen Qiang <quic_bqiang@...cinc.com>
Cc: Johan Hovold <johan+linaro@...nel.org>,
	Jeff Johnson <jjohnson@...nel.org>,
	Stephan Gerhold <stephan.gerhold@...aro.org>,
	ath12k@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wifi: ath12k: extend dma mask to 36 bits

On Mon, Mar 24, 2025 at 04:33:13PM +0800, Baochen Qiang wrote:
> On 3/22/2025 12:23 AM, 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
> > 
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>

> Reviewed-by: Baochen Qiang <quic_bqiang@...cinc.com>
> 
> With WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3 this is working, so:
> 
> Tested-by: Baochen Qiang <quic_bqiang@...cinc.com>

Thanks for reviewing and testing.

Johan