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SubjectRe: [PATCH 1/7] serial: 8250_dwlib: RS485 HW half duplex support
On Mon, Mar 7, 2022 at 12:00 AM Lukas Wunner <lukas@wunner.de> wrote:
> On Wed, Mar 02, 2022 at 11:56:00AM +0200, Ilpo Järvinen wrote:

...

> Does the DesignWare UART use dedicated DE and RE pins instead of
> the RTS pin? That would be quite unusual.

They are muxed with other UART pins on SoC level, but I don't remember
by heart which ones. According to the Synopsys datasheet they are
separate signals. It might be that I'm missing something, since the
last time I looked was last year.

...

> > + d->hw_rs485_support = device_property_read_bool(p->dev, "snps,rs485-interface-en");
> > + if (d->hw_rs485_support)
> > + p->rs485_config = dw8250_rs485_config;
> > +
>
> You wrote in the commit message that rs485 support is present from
> version 4.0 onward. Can't we just check the IP version and enable
> rs485 support for >= 4.0? That would seem more appropriate instead
> of introducing yet another new property.

AFAIU this is dependent on the IP syntheses. I.o.w. version 4.0+ is a
prerequisite, but doesn't automatically mean that there is a support.
Unfortunately there is no way to tell this clearly in the IP
configuration register.

--
With Best Regards,
Andy Shevchenko

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