Messages in this thread | | | Date | Mon, 18 Jul 2022 09:02:09 +0200 | Subject | Re: [PATCH 2/2] tty: serial: fsl_lpuart: writing a 1 and then a 0 to trigger a break character | From | Jiri Slaby <> |
| |
On 15. 07. 22, 13:52, Michael Walle wrote: >> Seems we have the different understanding of the break_ctl(port,ctl) >> callback. The original break_ctl(tty,-1) in lpuart will not send the >> break signal until we call break_ctl(tty,0). > > That is not correct. The TX linue goes low as soon as the SBK bit > is set. See below.
In that case…
>> Per my understanding of >> "If ctl is nonzero, the break signal should be transmitted", call >> break_ctl(tty,-1) is enough the send one break signal, now my patch >> makes the behavior align with my understanding. > > As I said, Greg should clarify here. > > In any case, I've checked the hardware (LS1028A) and as soon as you > set the SBK bit, the TX line goes low (TTL levels) as expected. It > will go to high again as soon as you clear the bit again. > > So to me it seems there is nothing wrong here. Also have a look > at man ioctl_tty: > > TIOCSBRK > Turn break on, that is, start sending zero bits. > > TIOCCBRK > Turn break off, that is, stop sending zero bits. > > So to send one break "character", you need to do ioctl(TIOCSBRK) > followed by an ioctl(TIOCCBRK).
… you're right.
regards, -- js
| |