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

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Message-ID: <c6e3b0c1-18fe-a9fa-0e72-d955809144e3@oss.qualcomm.com>
Date: Wed, 19 Mar 2025 18:24:57 +0530
From: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Vasanthakumar Thiagarajan <quic_vthiagar@...cinc.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 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.

diff --git a/drivers/net/wireless/ath/ath12k/core.c b/drivers/net/wireless/ath/ath12k/core.c

+       ab->single_chip_mlo_supp = false;


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.

Vasanth