[U-Boot] [PATCH v3 14/18] serial: 16550: allow the driver to support MediaTek serial

[Weijie Gao <weijie.gao@mediatek.com>]

On Mon, 2018-11-05 at 16:37 +0800, Ryder Lee wrote:
> On Mon, 2018-11-05 at 10:20 +0800, Ryder Lee wrote:
> > On Sat, 2018-11-03 at 00:09 -0600, Simon Glass wrote:
> > > Hi Ryder,
> > > 
> > > On 2 November 2018 at 09:15, Ryder Lee <ryder.lee@mediatek.com> wrote:
> > > > This patch adds an extra operation in ns16550.c to suuport MediaTek
> > > > SoCs as we have a highspeed register which influences the calcualtion
> > > > of the divisor.
> > > >
> > > > Note that we don't support the baudrate greater than 115200 currently.
> > > >
> > > > Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
> > > > Tested-by: Matthias Brugger <matthias.bgg@gmail.com>
> > > > Reviewed-by: Simon Glass <sjg@chromium.org>
> > > > ---
> > > >  drivers/serial/ns16550.c | 10 ++++++++++
> > > >  1 file changed, 10 insertions(+)
> > > 
> > > Actually it seems to me that we should have a compatible string for
> > > this and deal with this at run-time?
> > > 
> > > Is that easy to do here?
> > > 
> > 
> > How about this:
> > 
> > uart0: serial at 11002000 { 
> > 	compatible = "ns16550a"; 
> > 	....
> > 	mediatek,highspeed = <0>; 
> > 	....
> > 
> > Ryder
> > 
> 
> Sorry, I didn't get it right. I will add a compatible string in
> ns16550_serial_ids[] for MTK chips.
> 
> Ryder
> 
> 

Hi Simon,

We have tried the compatible string, but it made the ns16550 driver more
complicated.

To use the compatible string we have to add a new field in
ns16550_platdata, and change the flow of ns16550_serial_probe.
Moreover, it's totally useless for debug uart.

At present using a macro is the easiest way here.

Weijie