linux-kernel - Re: [PATCH 1/5] wifi: wilc1000: set preamble size to auto as default in wilc_init_fw

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Date: Fri, 19 Jan 2024 08:43:26 +0100
From: Alexis Lothoré <alexis.lothore@...tlin.com>
To: Ajay.Kathat@...rochip.com, kvalo@...nel.org
Cc: linux-wireless@...r.kernel.org, claudiu.beznea@...on.dev,
 davidm@...uge.net, thomas.petazzoni@...tlin.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] wifi: wilc1000: set preamble size to auto as default
 in wilc_init_fw_config()

On 1/18/24 17:52, Ajay.Kathat@...rochip.com wrote:
> On 1/18/24 08:08, Alexis Lothoré wrote:

[...]

>> "WILC driver currently applies some default configuration whenever the firmware
>> is initialized, and sets the default preamble size to short. However, despite
>> this passed option, firmware is also able to successfully connect to access
>> points only using long preamble, so this setting does not really enforce short
>> preambles and is misleading regarding applied configuration.
>>
>> Update default configuration and make it match the firmware behavior by passing
>> the existing WILC_FW_PREAMBLE_AUTO value (2 instead of 0). The updated setting
>> does not really alter firmware behavior since it is still capable to connect to
>> both short preamble and long preamble access points, but at list the setting now
>> expresses for real the corresponding firmware behavior"
>>
>> To give a bit of context around this one: I do not have access to the firmware
>> internals, I just took the patch from Ajay and I merely did some tests around it
>> with multiple APs (basically, making a WILC STA connect and ping the AP), and
>> ensured with wireshark to get at least one AP be really "locked" with long
>> preamble, with WILC managing to connect to it.
>>
> 
> Here are some more details about this change. It have been implemented
> to address the transmission(Tx) blackout issue observed in the 802.11b
> mode. The modification has no impact on the other modes, which will
> continue to work as they did in the previous implementation. This change
> will allow the 802.11b transmission(2, 5.5, 11Mbps) to use long preamble.

Ah, so it fixes a specific bug (and makes parts of my suggested description
wrong). Has there been any report about this "TX blackout issue" on the mailing
lists ? If so, we could enrich the message with some details from the report and
add some missing Reported-By/Fixes/Closes tags.

Alexis

-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com