linux-kernel - Re: [PATCH 1/3] wifi: ath11k: fix dest ring-buffer corruption

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Message-ID: <bc2afbd6-2876-4f36-81cf-ad8960588a02@quicinc.com>
Date: Thu, 5 Jun 2025 18:54:48 +0800
From: Baochen Qiang <quic_bqiang@...cinc.com>
To: Johan Hovold <johan@...nel.org>, Miaoqing Pan <quic_miaoqing@...cinc.com>
CC: Jeff Johnson <jeff.johnson@....qualcomm.com>,
        Johan Hovold
	<johan+linaro@...nel.org>,
        Jeff Johnson <jjohnson@...nel.org>, <linux-wireless@...r.kernel.org>,
        <ath11k@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH 1/3] wifi: ath11k: fix dest ring-buffer corruption



On 6/5/2025 6:17 PM, Johan Hovold wrote:
> On Thu, Jun 05, 2025 at 12:01:29PM +0800, Miaoqing Pan wrote:
>> On 6/5/2025 12:24 AM, Jeff Johnson wrote:
>>> On 6/3/2025 7:34 PM, Miaoqing Pan wrote:
>>>> We previously had extensive discussions on this topic in the
>>>> https://lore.kernel.org/linux-wireless/ecfe850c-b263-4bee-b888-c34178e690fc@quicinc.com/
>>>> thread. On my platform, dma_rmb() did not work as expected. The issue
>>>> only disappeared after disabling PCIe endpoint relaxed ordering in
>>>> firmware side. So it seems that HP was updated (Memory write) before
>>>> descriptor (Memory write), which led to the problem.
>>>
>>> Have all ath11k and ath12k firmware been updated to prevent this problem from
>>> the firmware side?
>>>
>> No, as this is not a widespread issue, and addressing it would require 
>> modifying the core underlying modules of the firmware. Therefore, we 
>> chose not to proceed with that approach but instead used the workaround 
>> patch I previously submitted.

If firmware has a concern, how about doing it in host? As I know it is only a register in
PCI config space?

> 
> I strongly suggest you fix this at the firmware level rather than try to
> work around it in the kernel to avoid playing whack-a-mole whenever a
> new (hard to track down) bug shows up.
> 
> The barriers should be enough, but if they are not then the firmware
> must be fixed.
> 
> Johan