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

[Miaoqing Pan <quic_miaoqing@quicinc.com>]

On 6/5/2025 6:54 PM, Baochen Qiang wrote:
> 
> 
> 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?
> 

No, host can only configure the RC, while the initialization of the EP 
can only be configured on the firmware side.

>>
>> 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
> 
This is beyond our control. After nearly three months of effort, we have 
decided to abandon it.