Re: [PATCH] serial: 8250: move mmp|pxa uart earlycon code and add xscale earlycon

[Jisheng Zhang]

On Sat, Jul 06, 2024 at 10:33:23PM +0000, Yixun Lan wrote:
> Hi 
> On 18:18 Sat 06 Jul     , Jisheng Zhang wrote:
> > There are two other drivers that bind to "mrvl,mmp-uart": the 8250_of
> > and the 8250_pxa. The previous one is generic and the latter is binded
> > to ARCH_PXA || ARCH_MMP. Now we may have pxa programming compatible
> > HW to support, making use of the generic 8250_of seems a good idea.
> > However, there's no earlycon support if we go with this solution. So
> > move the mmp|pxa-uart earlycon code to core 8250_early.c.
> > 
> > At the same, add xscale earlycon support too, only build test since
> > I have no xscale machine any more.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxx>
> > ---
> >  drivers/tty/serial/8250/8250_early.c | 11 +++++++++++
> >  drivers/tty/serial/8250/8250_pxa.c   | 16 ----------------
> >  2 files changed, 11 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c
> > index e3f482fd3de4..6176083d0341 100644
> > --- a/drivers/tty/serial/8250/8250_early.c
> > +++ b/drivers/tty/serial/8250/8250_early.c
> > @@ -171,6 +171,17 @@ OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
> >  OF_EARLYCON_DECLARE(uart, "nvidia,tegra20-uart", early_serial8250_setup);
> >  OF_EARLYCON_DECLARE(uart, "snps,dw-apb-uart", early_serial8250_setup);
> >  
> > +static int __init early_serial8250_rs2_setup(struct earlycon_device *device,
> > +					     const char *options)
> > +{
> > +	device->port.regshift = 2;
> just wondering if possible to introduce a generic earlycon sub option? so kernel

the 8250 ealycon can parse reg-shift from dt too, so no sub option is
needed. The reason I hardcoded here is: pxa-uart and xscale-uart doesn't
mandate "reg-shift" property in the binding, while I did see mmp-uart
mentions "reg-shift" is required in the DT binding.


> can parse reg-shift from command line parameter instead of hardcoding here,
> which would benefit more drivers (potentially without adding more OF_EARLYCON_DECLAREs..)
> 
> I mean something like this:
> Documentation/admin-guide/kernel-parameters.txt
> uart[8250],mmio32,<addr>[,options[,reg-shift=0,1,2,4 ..]]
> 
> > +
> > +	return early_serial8250_setup(device, options);
> > +}
> > +OF_EARLYCON_DECLARE(uart, "intel,xscale-uart", early_serial8250_rs2_setup);
> > +OF_EARLYCON_DECLARE(uart, "mrvl,mmp-uart", early_serial8250_rs2_setup);
> > +OF_EARLYCON_DECLARE(uart, "mrvl,pxa-uart", early_serial8250_rs2_setup);
> > +
> >  #ifdef CONFIG_SERIAL_8250_OMAP
> >  
> >  static int __init early_omap8250_setup(struct earlycon_device *device,
> > diff --git a/drivers/tty/serial/8250/8250_pxa.c b/drivers/tty/serial/8250/8250_pxa.c
> > index ba96fa913e7f..b5d937f6f3f9 100644
> > --- a/drivers/tty/serial/8250/8250_pxa.c
> > +++ b/drivers/tty/serial/8250/8250_pxa.c
> > @@ -165,22 +165,6 @@ static struct platform_driver serial_pxa_driver = {
> >  
> >  module_platform_driver(serial_pxa_driver);
> >  
> > -#ifdef CONFIG_SERIAL_8250_CONSOLE
> > -static int __init early_serial_pxa_setup(struct earlycon_device *device,
> > -				  const char *options)
> > -{
> > -	struct uart_port *port = &device->port;
> > -
> > -	if (!(device->port.membase || device->port.iobase))
> > -		return -ENODEV;
> > -
> > -	port->regshift = 2;
> > -	return early_serial8250_setup(device, NULL);
> > -}
> > -OF_EARLYCON_DECLARE(early_pxa, "mrvl,pxa-uart", early_serial_pxa_setup);
> > -OF_EARLYCON_DECLARE(mmp, "mrvl,mmp-uart", early_serial_pxa_setup);
> > -#endif
> > -
> >  MODULE_AUTHOR("Sergei Ianovich");
> >  MODULE_LICENSE("GPL");
> >  MODULE_ALIAS("platform:pxa2xx-uart");
> > -- 
> > 2.43.0
> > 
> 
> -- 
> Yixun Lan (dlan)
> Gentoo Linux Developer
> GPG Key ID AABEFD55