linux-kernel - Re: [PATCH net] wifi: ath12k: properly set single_chip_mlo_supp to true in ath12k_core

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Message-ID: <83c71791-dc34-54a5-7d67-9765aa2886e5@quicinc.com>
Date: Wed, 19 Mar 2025 22:53:43 +0530
From: Vasanthakumar Thiagarajan <quic_vthiagar@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        "Vasanthakumar
 Thiagarajan" <vasanthakumar.thiagarajan@....qualcomm.com>
CC: Krzysztof Kozlowski <krzk@...nel.org>, <neil.armstrong@...aro.org>,
        "Jeff
 Johnson" <jeff.johnson@....qualcomm.com>,
        Johannes Berg
	<johannes@...solutions.net>,
        Jeff Johnson <jjohnson@...nel.org>,
        "Aditya
 Kumar Singh" <quic_adisi@...cinc.com>,
        <linux-wireless@...r.kernel.org>, <ath12k@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH net] wifi: ath12k: properly set single_chip_mlo_supp to
 true in ath12k_core_alloc()



On 3/19/2025 7:03 PM, Dmitry Baryshkov wrote:
> On Wed, Mar 19, 2025 at 06:24:57PM +0530, Vasanthakumar Thiagarajan wrote:
>>
>>
>> On 3/19/2025 5:21 PM, Dmitry Baryshkov wrote:
>>> On Wed, Mar 19, 2025 at 05:02:39PM +0530, Vasanthakumar Thiagarajan wrote:
>>>>
>>>>
>>>> On 3/19/2025 3:57 PM, Krzysztof Kozlowski wrote:
>>>>> On 19/03/2025 10:06, Vasanthakumar Thiagarajan wrote:
>>>>>>>>> ---
>>>>>>>>> base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6
>>>>>>>>> change-id: 20250303-topic-ath12k-fix-crash-49e9055c61a1
>>>>>>>>>
>>>>>>>>> Best regards,
>>>>>>>>
>>>>>>>> NAK since this will break QCN
>>>>>>>> There is a series under internal review to address MLO issues for WCN chipsets
>>>>>>>
>>>>>>> ???
>>>>>>>
>>>>>>> The original commit is wrong, this fixes the conversion, nothing else.
>>>>>>
>>>>>> Nope. Driver changes to enable MLO with WCN chipset are not there yet.
>>>>>> Setting the mlo capability flag without having required driver changes
>>>>>> for WCN chipset will likely result in firmware crash. So the recommendation
>>>>>> is to enable MLO (in WCN) only when all the necessary driver changes
>>>>>> (in development, public posting in near future) are in place.
>>>>> Really, these are your answers? There is regression and first reply is
>>>>> upstream should wait for whatever you do internally. Second answer is
>>>>> the same - public posting in near future?
>>>>>
>>>>
>>>> May be I was not clear in my response. I was not telling MLO bug fixes were
>>>> in the development. Actually the MLO feature itself is not enabled
>>>> yet with WCN chip sets. Any code changes enabling it without full feature
>>>> support would result in firmware crashes with the existing firmware binaries
>>>> available in upstream.
>>>
>>> Is there an undocumented change of the behaviour in the commit
>>> 46d16f7e1d14 ("wifi: ath12k: rename mlo_capable_flags to
>>> single_chip_mlo_supp")?
>>>
>>
>> diff --git a/drivers/net/wireless/ath/ath12k/qmi.c b/drivers/net/wireless/ath/ath12k/qmi.c
>>
>> -       if (resp.single_chip_mlo_support_valid) {
>> -               if (resp.single_chip_mlo_support)
>> -                       ab->mlo_capable_flags |= ATH12K_INTRA_DEVICE_MLO_SUPPORT;
>> -               else
>> -                       ab->mlo_capable_flags &= ~ATH12K_INTRA_DEVICE_MLO_SUPPORT;
>> -       }
>>
>> The above logic seems to keep the initialized intra MLO support even when
>> single_chip_mlo_support_valid is not set. The above code removal is correct as
>> MLO support can not be enabled in host when firmware does not advertise it.
> 
> Ack
> 
>>
>> diff --git a/drivers/net/wireless/ath/ath12k/core.c b/drivers/net/wireless/ath/ath12k/core.c
>>
> 
> You skipped an important chunk:
> 
> -	ab->mlo_capable_flags = ATH12K_INTRA_DEVICE_MLO_SUPPORT;
>> +       ab->single_chip_mlo_supp = false;
> 
> Is this an _undocumented_ change? I think it is. If the developer has
> described that the commit disables MLO, there would be no such
> questions.
> 

Right. Since MLO was WCN was not supported, this default configuration was
changed to avoid potential issues due to partial MLO configurations with
official upstream firmware binaries.

>> diff --git a/drivers/net/wireless/ath/ath12k/qmi.c b/drivers/net/wireless/ath/ath12k/qmi.c
>>
>> +       if (resp.single_chip_mlo_support_valid &&
>> +           resp.single_chip_mlo_support)
>> +               ab->single_chip_mlo_supp = true;
>>
>> The above code does it in right way. Overriding firmware MLO capability as done
>> in the submitted patch under review is obviously wrong. The firmware used to report
>> the issue seems to have an odd behavior: 1. it does not seem to advertise MLO
>> capability in single_chip_mlo_support bit and 2. expects configurations to enable
>> MLO from host. None of the WCN firmware available in upstream either advertises
>> MLO capability or expects configurations to enable MLO from host.
> 
> Additionally, from the commit message:
> 
>      For the WCN7850 family of chipsets, since the event is not supported,
>      assumption is made that single chip MLO is supported.
> 
> However the code doesn't contain that change. Instead single chip MLO is
> unconditionally disabled.
>

This text in commit message seems to be a miss. This should have been
removed as the merged patch version completely disables MLO for WCN
chip.

Vasanth