[PATCH] arm64: add support for 8250/16550 earlyprintk

[marc.zyngier@arm.com (Marc Zyngier)]

On Fri,  1 Mar 2013 11:30:26 +0530, Anup Patel <anup.patel@linaro.org>
wrote:
> This patch adds support for using earlyprintk with 8250/16550 UART
ports.
> 
> The 8250/16550 UART can either have 8-bit or 32-bit aligned registers
> which is HW vendor dependent.
> 
> Kernel args for 8-bit aligned regs:
> earlyprintk=uart8250-8bit,<phys_address>
> 
> Kernel args for 32-bit aligned regs:
> earlyprintk=uart8250-16bit,<phys_address>
                       ^^^^^

Please fix this comment to match the actual code.

> Signed-off-by: Anup Patel <anup.patel@linaro.org>
> ---
>  arch/arm64/kernel/early_printk.c |   23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/arch/arm64/kernel/early_printk.c
> b/arch/arm64/kernel/early_printk.c
> index 7e320a2..d57f300 100644
> --- a/arch/arm64/kernel/early_printk.c
> +++ b/arch/arm64/kernel/early_printk.c
> @@ -24,11 +24,32 @@
>  #include <linux/io.h>
>  
>  #include <linux/amba/serial.h>
> +#include <uapi/linux/serial_reg.h>

You do not need to refer to uapi here. <linux/serial_reg.h> should be
enough.

>  static void __iomem *early_base;
>  static void (*printch)(char ch);
>  
>  /*
> + * 8250/16550 (8-bit aligned registers) single character TX.
> + */
> +static void uart8250_8bit_printch(char ch)
> +{
> +	while (!(readb_relaxed(early_base + UART_LSR) & UART_LSR_THRE))
> +		;
> +	writeb_relaxed(ch, early_base + UART_TX);
> +}
> +
> +/*
> + * 8250/16550 (32-bit aligned registers) single character TX.
> + */
> +static void uart8250_32bit_printch(char ch)
> +{
> +	while (!(readl_relaxed(early_base + (UART_LSR << 2)) & UART_LSR_THRE))
> +		;
> +	writel_relaxed(ch, early_base + (UART_TX << 2));
> +}
> +
> +/*
>   * PL011 single character TX.
>   */
>  static void pl011_printch(char ch)
> @@ -47,6 +68,8 @@ struct earlycon_match {
>  
>  static const struct earlycon_match earlycon_match[] __initconst = {
>  	{ .name = "pl011", .printch = pl011_printch, },
> +	{ .name = "uart8250-8bit", .printch = uart8250_8bit_printch, },
> +	{ .name = "uart8250-32bit", .printch = uart8250_32bit_printch, },
>  	{}
>  };

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