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From: Michel Macena Oliveira <michel@austral-dynamics.com>
To: Itai Handler <itai.handler@gmail.com>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: Serial port driver usage and status
Date: Thu, 16 Jul 2020 17:20:10 -0300
Message-ID: <CAKkbJ-wDsGO+ZHKZFkPfUL113ONc=NNNeShQkLf+ZH82iaBTEQ@mail.gmail.com> (raw)
In-Reply-To: <CAFpOueQm5MhbrV53=kAcw=ES2LzsZPkmX2SqTVKuYTf0QDt=7w@mail.gmail.com>

Thanks for the answer,
Yes I wrote a code that works with  /dev/tty* serial using termios.h.
I thought exactly what you suggested, to use a dedicated thread, but
how to properly implement it?
I mean in a simple way, just need to put open and write calls inside
the high priority (RT) thread?

Current kernel: 4.4.208-rt198 #1 SMP PREEMPT RT

Em qui., 16 de jul. de 2020 às 16:26, Itai Handler
<itai.handler@gmail.com> escreveu:
>
> Hi Michel,
>
> On 7/16/20, Michel Macena Oliveira <michel@austral-dynamics.com> wrote:
> > Hi, sorry for my newbie question,
> > What is the status of the serial port driver?
> > I've written some code to use serial ports  for the generic kernel linux,
> > And now I want to write something similar for the real time kernel, do
> > I have to use some specific library, flags or something or is it just
> > the same settings?
> >
> > I'm asking because now I need to take into account the serial access
> > in the scheduler to ensure a real time behavior .
> >
> > Any help, advice, hint or tips would be appreciated.
> >
>
> Do you mean that you wrote some code that works with a /dev/tty* serial port?
>
> In some kernel versions (e.g 4.19) we saw high latencies in the rx
> path of serial drivers.
> I think that this is due to rx handled in the context of a workqueue
> which also handles other system activities.
> We found a workaround to this problem. If I remember correctly we
> create a dedicated thread for the port and assign it a high priority.
>
> Itai Handler

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-16 17:29 Michel Macena Oliveira
2020-07-16 19:26 ` Itai Handler
2020-07-16 20:20   ` Michel Macena Oliveira [this message]
2020-07-16 20:40     ` Itai Handler
2020-07-16 20:40     ` Austin Schuh
2020-08-05 18:29       ` Michel Macena Oliveira
2020-08-05 19:21         ` Itai Handler
2020-08-05 19:52           ` Michel Macena Oliveira
2020-08-06 19:56             ` Itai Handler
2020-08-11 14:43               ` Michel Macena Oliveira
2020-08-11 19:07                 ` Austin Schuh

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