Re: [PATCH] Revert "serial: max310x: rework RX interrupt handling"

[Alexander Shiyan <shc_work@mail.ru>]

On Wed, 17 Feb 2021 23:53:45 +0100
Thomas Petazzoni <thomas.petazzoni@bootlin.com> wrote:

Hello.

> > This reverts commit fce3c5c1a2d9cd888f2987662ce17c0c651916b2.
> > 
> > FIFO is triggered 4 intervals after receiving a byte, it's good
> > when we don't care about the time of reception, but are only
> > interested in the presence of any activity on the line.
> > Unfortunately, this method is not suitable for all tasks,
> > for example, the RS-485 protocol will not work properly,
> > since the state machine must track the request-response time
> > and after the timeout expires, a decision is made that the device
> > on the line is not responding.
> > 
> > Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
> 
> Thanks for the feedback. Should we switch between one mode and the
> other depending on whether RS232 or RS485 is used ? Or is there some
> appropriate user-space interface to ask the UART driver to tweak this
> kind of configuration ?

I wrote a little inaccurately, I did not mean a physical interface RS-485,
but rather a time-critical MODBUS protocol. (In our case it used on top on RS-485).

I do not know how best to solve this problem, it may be an additional parameter
for the devicetree, but in this case it is not clear how to manage it if the
devicetree is not used ...
This could be a Kconfig item (but something's not very good either).
Probably the best solution is to adapt some kind of IOCTL (or control via SYSFS).

In any case i feel free to test your modifications to the driver.

Thanks!
-- 
Alexander Shiyan <shc_work@mail.ru>