linux-kernel - Re: [PATCH V2 1/1] USB: serial: f81232: fix incomplete serial port generation

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Message-ID: <fd3e97cf-6f92-4921-9482-e0d6863a46b2@fintek.com.tw>
Date: Tue, 2 Dec 2025 13:40:28 +0800
From: Peter Hong <peter_hong@...tek.com.tw>
To: Johan Hovold <johan@...nel.org>
CC: <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <tom_tsai@...tek.com.tw>,
        <yu_chen@...tek.com.tw>
Subject: Re: [PATCH V2 1/1] USB: serial: f81232: fix incomplete serial port
 generation

Hi,

Johan Hovold 於 2025/12/1 下午 09:38 寫道:
> On Fri, Nov 28, 2025 at 04:52:44PM +0800, Ji-Ze Hong (Peter Hong) wrote:
>> The Fintek F81532A/534A/535/536 family relies on the
>> F81534A_CTRL_CMD_ENABLE_PORT (116h) register during initialization to
>> both determine serial port status and control port creation. If the
>> driver experiences fast load/unload cycles, the device state may becomes
>> unstable, resulting in the incomplete generation of serial ports.
>>
>> Performing a dummy read operation on the register prior to the initial
>> write command resolves the issue. This clears the device's stale internal
>> state. Subsequent write operations will correctly generate all serial
>> ports.
>>
>> Tested on: HygonDM1SLT(Hygon C86 3250 8-core Processor)
>>
>> Signed-off-by: Ji-Ze Hong (Peter Hong) <peter_hong@...tek.com.tw>
>> ---
>> Changelog:
>> v2:
>> 	1. remove loop in accessor function.
> Thanks for verifying.
>
> Did you try removing the retry loop also in the set_register() helper?
> Perhaps that's no longer needed after the dummy read.

I will try removing the retry loop in set_register() helper.
If that worked, could I use the same patch file or series of patches?

Thanks,


-- 

*洪繼澤 **Peter Hong*

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