linux-kernel - Re: ath12k: REO status on PPC does not work

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Message-ID: <ff8287fc-7122-42e7-b6ab-550576b5d599@oss.qualcomm.com>
Date: Tue, 19 Aug 2025 15:26:34 +0800
From: Baochen Qiang <baochen.qiang@....qualcomm.com>
To: Alexander Wilhelm <alexander.wilhelm@...termo.com>
Cc: Jeff Johnson <jjohnson@...nel.org>, ath12k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: ath12k: REO status on PPC does not work



On 8/19/2025 2:59 PM, Alexander Wilhelm wrote:
> Am Tue, Aug 19, 2025 at 02:38:38PM +0800 schrieb Baochen Qiang:
>>
>>
>> On 8/15/2025 4:13 PM, Alexander Wilhelm wrote:
>>> Hello devs,
>>>
>>> I'm currently working on getting the 'ath12k' driver running on a big endian
>>> PowerPC platform and have encountered the following issue.
>>>
>>> In the function 'ath12k_dp_rx_process_reo_status', the REO status is determined
>>> by inspecting memory that the hardware has previously written via DMA.
>>> Specifically, during the call to 'ath12k_hal_srng_access_begin', the driver
>>> reads the value of 'hp_addr' for the destination ring (in my case, always with
>>> ID 21). On the big endian platform, this value is consistently 0, which prevents
>>> the REO status from being updated.
>>
>> This does not seem an endian issue to me, because either of them we should get a value
>> other than 0.
> 
> Really? I always assumed the value remains 0 until the firmware writes something
> to memory and moves the head pointer of the SRNG ring buffer. By the way, I've

correct!

> already implemented the missing endianness conversions for reading from and
> writing to ring buffer pointers like this one:
> 
>     hp = le32_to_cpu(*srng->u.dst_ring.hp_addr);

I was actually meaning that, when hp get updated by firmware, either with or without
le32_to_cpu conversion, we should get a value other than 0.

So in your cause I am suspecting that hardware/firmware has never sent any REO status to
host.

> 
>>> Interestingly, DMA read/write accesses work fine for other rings, just not for
>>> this one. What makes the REO status ring so special? I couldn’t find anything in
>>> the initialization routine that would explain the difference.
>>>
>>> Could anyone give me a hint on what I should be looking for?
>>>
>>>
>> What hardware are you using? WCN7850 or QCN9274?
> 
> I'm using QCN9274-based dualmac modules.

sure

> >
> Best regards
> Alexander Wilhelm

so did you see any obvious issue?