Re: [RFC 08/11] MIPS: ralink: adds early_printk support

[Florian Fainelli <florian@openwrt.org>]

Hey John,

Le 23/01/2013 13:05, John Crispin a écrit :
> Add the code needed to make early printk work.
>
> Signed-off-by: John Crispin <blogic@openwrt.org>
> ---
>   arch/mips/ralink/early_printk.c |   43 +++++++++++++++++++++++++++++++++++++++
>   1 file changed, 43 insertions(+)
>   create mode 100644 arch/mips/ralink/early_printk.c
>
> diff --git a/arch/mips/ralink/early_printk.c b/arch/mips/ralink/early_printk.c
> new file mode 100644
> index 0000000..c610084
> --- /dev/null
> +++ b/arch/mips/ralink/early_printk.c
> @@ -0,0 +1,43 @@
> +/*
> + *  This program is free software; you can redistribute it and/or modify it
> + *  under the terms of the GNU General Public License version 2 as published
> + *  by the Free Software Foundation.
> + *
> + *  Copyright (C) 2011-2012 Gabor Juhos <juhosg@openwrt.org>
> + */
> +
> +#include <linux/io.h>
> +#include <linux/serial_reg.h>
> +
> +#include <asm/addrspace.h>
> +
> +/* UART registers */
> +#define EARLY_UART_BASE         0x10000c00
> +
> +#define UART_REG_RX             0
> +#define UART_REG_TX             1
> +#define UART_REG_IER            2
> +#define UART_REG_IIR            3
> +#define UART_REG_FCR            4
> +#define UART_REG_LCR            5
> +#define UART_REG_MCR            6
> +#define UART_REG_LSR            7

Is that really required considering that you already include 
serial_reg.h and could use defines from there?

At some point I think that we might be able to come up with a some kind 
of generic 8250 earlyprintk code where people just tell what's the base 
address of their UART. Something like:

#define UART_BASE	KSEG1ADDR(MY_UART_BASE)
#include <asm/8250-earlyprintk.h>

> +
> +static inline void uart_w32(u32 val, unsigned reg)
> +{
> +	__raw_writel((val),
> +		(void __iomem *)(KSEG1ADDR(EARLY_UART_BASE) + 4 * (reg)));
> +}
> +
> +static inline u32 uart_r32(unsigned reg)
> +{
> +	return __raw_readl(
> +		(void __iomem *)(KSEG1ADDR(EARLY_UART_BASE) + 4 * (reg)));
> +}
> +
> +void prom_putchar(unsigned char ch)
> +{
> +	while (((uart_r32(UART_REG_LSR)) & UART_LSR_THRE) == 0);
> +	uart_w32(UART_REG_TX, ch);
> +	while (((uart_r32(UART_REG_LSR)) & UART_LSR_THRE) == 0);
> +}
>