quoted

quoted

quoted

Again, doesn't matter, since it's the DTB that provides the default
state.  So, back when it was authored, the default state was HW
flow-control disabled.  And in a newer DTB (again, until I follow-up
with more changes), the defaults for UART 1 and UART 2 are HW
flow-control disabled.

Your issue seems to be that you've assumed since we now provide the
possibility of a "manual-rts" state, then the "default" state should
*only* be HW flow-control capable, which is not the case.

No my feedback was that it would be clearer & simpler to make manual-rts the
'default' state, and 'hw-flow-control' the optional state.

Absolutely not.  The use of "manual-rts" is the corner-case here and
is not normally required.

See below.

quoted

The "default" state should normally be
populated with whatever pins are available i.e. all 4 pins (including
"rts, cts") if they are wired up and only 2 pins (just "tx, rx") if
they are not.

Yep OK, I agree :)

\o/

quoted

The submission of "manual-rts" is only required if the
RTS pin is required for some other purpose e.g. resetting a uC on a
draughtboard.

All UARTs the SoC have the same st-asc IP, which suffers from the same
hw flow control limitation. Also all instances on the SoC have rts/cts
pins, the only limitation is board wiring.

So I can't see why would you ever *not* want to deploy this dynamic pin
switching solution if rts/cts is wired up at board level now the facility
exists?

Mainly because it's surplus to requirement, in that there is very
seldom any point in manually toggling the RTS line (at least to my
knowledge).  I figure we'd add >1 Pinctrl states only when the need
arises, thus keeping the DTS' as simple as possible.

Also regarding the naming of the second pin group, 'manual-rts' seems like
a bad name as a logical extension of this set is to also offer the same
dynamic switching for the CTS line.

Maybe a better name would be 'tx-rx-only' or 'no-rts-cts'.

Works for me.  Will fix.

quoted

quoted

quoted

It's the
'uart-has-rtscts' property which determines this *not* whether the
second state has been provided.

Yep, which is why IMO it makes more sense for the optional pin group to be the hw
flow control pins which are obtained if the uart-has-rtscts property is present.

There would normally only be one pin group.  Your method would insist
we always provided 2, which would be surplus to requirement.

Yep OK, agree with your point.

\o/

Yep OK, I agree.

\o/

Yep OK, I agree.

\o/

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org ? Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog