Re: [Regression] CH341 USB-serial converter passes data in 32 byte chunks

From: Johan Hovold <johan@kernel.org>
To: Jonathan Woithe <jwoithe@just42.net>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	linux-serial@vger.kernel.org, linux-usb@vger.kernel.org,
	Aidan Thornton <makosoft@gmail.com>,
	Grigori Goronzy <greg@chown.ath.cx>,
	Michael Hanselmann <public@hansmi.ch>
Subject: Re: [Regression] CH341 USB-serial converter passes data in 32 byte chunks
Date: Mon, 18 Jul 2022 16:16:03 +0200	[thread overview]
Message-ID: <YtVrI6FRZRKKALPN@hovoldconsulting.com> (raw)
In-Reply-To: <YtUfcSOTl/ia+ahL@hovoldconsulting.com>

On Mon, Jul 18, 2022 at 10:53:06AM +0200, Johan Hovold wrote:

> From 82faf260d13c9f01e4af664f31231e5d88d7e4f1 Mon Sep 17 00:00:00 2001
> From: Johan Hovold <johan@kernel.org>
> Date: Mon, 18 Jul 2022 10:21:41 +0200
> Subject: [PATCH] USB: serial: ch341: fix disabled tx timer on older devices
> 
> At least one older CH341 appears to have the TX timer enable bit
> inverted so that setting it disables the TX timer and prevents the FIFO
> from emptying until it is full.
> 
> Only set the TX timer enable bit for devices with version newer than
> 0x27.
> 
> Also try restoring an older init command before updating the line
> settings to see if it has any effect on a lost first byte after
> initialisation.
> 
> Reported-by: Jonathan Woithe <jwoithe@just42.net>
> Link: https://lore.kernel.org/r/Ys1iPTfiZRWj2gXs@marvin.atrad.com.au
> Not-Signed-off-yet-by: Johan Hovold <johan@kernel.org>

s/TX/RX/ ...

Johan