On Fri, 1 Mar 2013 11:30:26 +0530, Anup Patel <anup.pa...@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.pa...@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, },
> {}
> };
--
Fast, cheap, reliable. Pick two.
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