Re: [PATCH v5 2/5] Bluetooth: hci_qca: Deassert RTS while baudrate change command

On Tue, Jan 15, 2019 at 03:46:28PM -0800, Matthias Kaehlcke wrote:

Using RTS seems|ed like a nice solutions, since it's the native way to
prevent the controller from sending data, instead of doing some custom
hack. However Johan seems to be fairly convinced that flow control and
manual toggling of RTS can be problematic, and we have seen that
disabling flow control has its own problems. Maybe it's time to
consider other solutions like the DISCARD_RX flag we discussed
earlier. Not that I really liked this custom solution, but in the end
it might be a more robust way to address the issue.

Johan/Marcel/others: Do you have any further ideas or input on this?

I don't see why deasserting RTS wouldn't work, well at least as long as
the RTS signal is wired correctly.

My point was simply that calling serdev_device_set_rts() will generally
not work unless you first disable automatic (i.e. hw-managed) flow
control using serdev_device_set_flow_control(). The exact behaviour is
serial-controller dependent, but I assume the driver needs to be
platform agnostic.

Johan