Re: [PATCH] ns16550: Fix DM serial operation with non-DM SPL

[Sergei Antonov <saproj@gmail.com>]

On Tue, 17 Jan 2023 at 19:14, Andre Przywara <andre.przywara@arm.com> wrote:
>
> On Tue, 17 Jan 2023 16:12:54 +0300
> Sergei Antonov <saproj@gmail.com> wrote:
>
> Hi Sergei,
>
> > On Tue, 17 Jan 2023 at 15:10, Andre Przywara <andre.przywara@arm.com> wrote:
> >
> > > -#if CONFIG_IS_ENABLED(DM_SERIAL) && !defined(CONFIG_SYS_NS16550_REG_SIZE)
> > > +#if CONFIG_IS_ENABLED(DM_SERIAL)
> > >  /*
> > >   * For driver model we always use one byte per register, and sort out the
> > >   * differences in the driver
> > >   */
> > > +#undef CONFIG_SYS_NS16550_REG_SIZE
> > >  #define CONFIG_SYS_NS16550_REG_SIZE (-1)
> > >  #endif
> >
> > What if I have DM_SERIAL and a 16550 UART with 32-bit registers?
>
> So does that break for you?
> Because it should still work, I think, since (as the comment says) we just
> use the struct to get the register *number*. The actual register size is
> worked out from the DT, and multiplied in later.
>
> > Before 9591b63531fa the register size of 8 was enforced for DM_SERIAL.
>
> 8? Or 4?

Oh, I meant 8-bit. So under DM_SERIAL:
CONFIG_SYS_NS16550_REG_SIZE is -1
UART_REG(x) is unsigned char x

> What does your reg-shift DT property say? Is that in your DT?

I did not have "reg-shift" property. Thanks for telling about it. Now
that I have these properties in DT my UART works.
  reg-io-width = <4>;
  reg-shift = <2>;

I also had to add this config parameter to make debug uart work:
CONFIG_DEBUG_UART_SHIFT=2

Thanks!