Re: [PATCH net-next v10 2/2] net: wwan: mhi_wwan_ctrl: drive DTR/RTS via the IP_CTRL channel

[Peter Hunt]

Thanks for the review.

[Medium] a DTR/RTS request made while IP_CTRL is not bound is lost:
agreed. It needs IP_CTRL to bind after the AT port has been opened. On
the EM919x/EM929x, IP_CTRL (channels 18/19) is probed before DUN
(32/33), so outside async probing this only happens after a sysfs
unbind/rebind of mhi_wwan_dtr or a failed IP_CTRL probe. The fix is for
mhi_wwan_dtr_probe() to resend the current state of the AT ports on its
controller.

[Low] coalescing can swallow a DTR drop on a quick close and reopen:
agreed, a drop matters on its own for a modem set to AT&D2. The fix is
to never coalesce away a pending drop, and send it before the latest
state.

Both are corner cases outside normal operation, which I've tested on an
EM9291, including bursts of 10,000 DTR changes ending in either state.
I'd propose to address them in a small follow-up patch on top of this
series, but I'm happy to fold them into a v11 instead if the
maintainers prefer.