[PATCH] TMS570 console driver, SCI frame error (baudrate calculation error)

[Joel Sherrill]

First, the patch commit message needs to reference the ticket (#4903).

It would be nice to have Pavel's feedback but the submitter of
https://devel.rtems.org/ticket/4903
provided the fix but not in patch format.  What do you think we should do
beyond trust the
submitter of the ticket?

bsps/arm/tms570/console/tms570-sci.c: tms570_sci_set_attributes()

/* Apply baudrate to the hardware */
  baudrate *= 2 * 16;
  bauddiv = (BSP_PLL_OUT_CLOCK + baudrate / 2) / baudrate;
  ctx->regs->BRS = bauddiv? bauddiv - 1: 0;


replacing with 2 fixed frame error

ctx->regs->BRS = bauddiv? bauddiv - 2: 0;

there is issue in baudrate calculation

On Tue, Jul 11, 2023 at 12:52 PM Gedare Bloom <gedare at rtems.org> wrote:

> Hi Zack,
>
> Thanks for the patch. Someone should probably test it, or identify in
> the documentation why this calculation was off-by-1. Pavel, any clues?
>
> Gedare
>
> On Sun, Jul 9, 2023 at 10:09 PM zack <zakthertemsdev at gmail.com> wrote:
> >
> > Fixes #4903
> > diff --git a/bsps/arm/tms570/console/tms570-sci.c
> b/bsps/arm/tms570/console/tms570-sci.c
> > index 768770a4c8..59a0b7e6f1 100644
> > --- a/bsps/arm/tms570/console/tms570-sci.c
> > +++ b/bsps/arm/tms570/console/tms570-sci.c
> > @@ -311,7 +311,7 @@ bool tms570_sci_set_attributes(
> >    /* Apply baudrate to the hardware */
> >    baudrate *= 2 * 16;
> >    bauddiv = (BSP_PLL_OUT_CLOCK + baudrate / 2) / baudrate;
> > -  ctx->regs->BRS = bauddiv? bauddiv - 1: 0;
> > +  ctx->regs->BRS = bauddiv? bauddiv - 2: 0;
> >
> >    ctx->regs->GCR1 |= TMS570_SCI_GCR1_SWnRST | TMS570_SCI_GCR1_TXENA |
> >                       TMS570_SCI_GCR1_RXENA;
> > --
> > 2.34.1
> >
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