linux-kernel - Re: Break doesn't work on a CP2105

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Message-ID: <ZH2LkKE83kHrIRWH@hovoldconsulting.com>
Date:   Mon, 5 Jun 2023 09:15:28 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Corey Minyard <minyard@....org>
Cc:     Craig Shelley <craig@...rotron.org.uk>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-usb@...r.kernel.org
Subject: Re: Break doesn't work on a CP2105

On Sun, Jun 04, 2023 at 03:11:43PM -0500, Corey Minyard wrote:
> On Sun, Jun 04, 2023 at 02:17:16PM +0200, Johan Hovold wrote:

> > I just verified break signalling on the first port of my CP2105 using a
> > logic analyser and everything seems to work as expected.
> > 
> > There's also no mention of any issue with break in the errata.
> > 
> > Could you check which firmware revision you have by enabling debugging
> > and reconnecting the device?

> [    4.253869] usb 2-1.2: new full-speed USB device number 3 using ehci-pci
> [    4.342570] usb 2-1.2: New USB device found, idVendor=10c4, idProduct=ea70, bcdDevice= 1.00
> [    4.350939] usb 2-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=5
> [    4.358259] usb 2-1.2: Product: CP2105 Dual USB to UART Bridge Controller
> [    4.365052] usb 2-1.2: Manufacturer: Silicon Labs
> [    4.369765] usb 2-1.2: SerialNumber: 01070456
> [    4.374925] cp210x 2-1.2:1.0: cp210x converter detected
> [    4.381086] cp210x 2-1.2:1.0: cp210x_get_fw_version - 1.18.1
> [    4.386915] usb 2-1.2: cp210x converter now attached to ttyUSB0
> [    4.393529] cp210x 2-1.2:1.1: cp210x converter detected
> [    4.399835] cp210x 2-1.2:1.1: cp210x_get_fw_version - 1.18.1
> [    4.405657] usb 2-1.2: cp210x converter now attached to ttyUSB1

So we have the same firmware revision.
 
> This is an embedded reference board, I guess there is some probability
> that this is just broken on this board, though I'm not quite sure how.

Is the port accessible somehow so that you could hook up a scope or
logic analyser? Or is that what you did already when you mentioned
seeing garbage sent after 2.5 seconds?

That last bit seems to match the behaviour I see with the second, SCI
port, where the last character sent is resent when trying to signal a
break.

Johan