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

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Message-ID: <20240706223323.GYA367.dlan.gentoo>
Date: Sat, 6 Jul 2024 22:33:23 +0000
From: Yixun Lan <dlan@...too.org>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] serial: 8250: move mmp|pxa uart earlycon code and add
 xscale earlycon

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@...nel.org>
> ---
>  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
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