Re: cp210x module broken in 5.12.5 and 5.12.6, works in 5.11.21 (with bisection)

[Johan Hovold <johan@kernel.org>]

On Mon, Jun 07, 2021 at 09:44:59AM -0700, David Frey wrote:
> On Sat, Jun 5, 2021 at 3:13 AM Johan Hovold <johan@kernel.org> wrote:
> >
> > I found an errata for A01 on here, but no mention if this particular
> > bug:
> >
> >         https://www.silabs.com/documents/public/pcns/190315471-CP2102N-Product-Revision-with-Datasheet-and-Errata-Update.pdf
> 
> I believe this document has some more errata details:
> https://www.silabs.com/documents/public/errata/cp2102n-errata.pdf'

Thanks for the link.

This seems to confirm that this is a known issue with A01 that was fixed
in A02:

	3.6 CP2102N_E104 – IO Exception in .NET Applications when
	Manually Controlling RTS

	The CP2102N uses the incorrect byte of the SERIAL_HANDFLOW
	structure
	(https://msdn.microsoft.com/en-us/library/windows/hard-
	ware/jj680685(v=vs.85).aspx) to control the RTS signal. Instead
	of looking at the first byte of FlowReplace, the device is
	reading the first byte of the XonLimit and interpreting that as
	the first byte of FlowReplace.

	Applications written in .NET set the Xon/Xoff limits to 160,
	equal to 0xA0, which the CP2102N interprets as hardware flow
	control, and so it returns an error when manually setting RTS.

Now we just need to figure out how to determine the firmware revision.

Johan