linux-kernel - Re: [PATCH V1 1/1] USB: serial: f81232: fix incomplete serial port generation

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Message-ID: <aO5uAUknTLOWdvUY@hovoldconsulting.com>
Date: Tue, 14 Oct 2025 17:36:33 +0200
From: Johan Hovold <johan@...nel.org>
To: "Ji-Ze Hong (Peter Hong)" <peter_hong@...tek.com.tw>
Cc: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, tom_tsai@...tek.com.tw,
	yu_chen@...tek.com.tw, hpeter+linux_kernel@...il.com
Subject: Re: [PATCH V1 1/1] USB: serial: f81232: fix incomplete serial port
 generation

On Wed, Oct 08, 2025 at 10:38:58AM +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.

Do I understand correctly that you're only seeing this issue if you're
unloading and reloading the module (or rebinding the driver through
sysfs)?

> 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.

Does this mean that the retry loop is no longer needed? Can it now be
removed in either or both accessor functions perhaps?

Johan