Re: Incorrect UART in /tty/serial/8250

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Mar 28, 2024 at 02:34:10PM -0500, Joshua Droney wrote:
> Hello!
> 
> My name is Josh. I'm currently employed at Commtech, Inc.
> (https://fastcomproducts.com/). I'm following the instructions at
> https://kernelnewbies.org/FoundBug to report this issue. Please let me
> know if this is incorrect.
> 
> We (Commtech) have several serial boards, but the board in question is
> the '422/2-PCIe'. This board does not exist, but someone added it to
> the Linux kernel at some point in the past. This wouldn't be a
> problem, except that the board ID that was used for this non-existent
> board (0x22) was ultimately used for a different REAL board, with a
> different UART. Instead of a xr172358, we use a 16C950 on the real
> board. But the Linux kernel finds our other board ID, and tries to
> initialize it as an exar chip and fails. I don't know much about the
> kernel, but I believe the lines in question are:
> 
> https://github.com/torvalds/linux/blob/master/drivers/tty/serial/8250/8250_exar.c#L47
> https://github.com/torvalds/linux/blob/master/drivers/tty/serial/8250/8250_exar.c#L925
> 
> You can see that we have a different board with device ID 0x22 here:
> https://admin.pci-ids.ucw.cz/read/PC/18f7
> 
> The 422/4-PCIe exists (0x20), the 422/8-PCIe exists (0x21), but the
> 422/2-PCIe was never created and its device id was used for a
> different board (0x22, the SuperFSCC/4-LVDS-PCIe).

Can you please submit a patch that fixes this?  We'll be glad to take
it.  If you need help making it, please let us know.

thanks,

greg k-h