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

[Anup Patel]

On 1 March 2013 13:47, Marc Zyngier <marc.zyngier at arm.com> wrote:
>
> On Fri,  1 Mar 2013 11:30:26 +0530, Anup Patel <anup.patel at 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.

Sure, I will fix this.

>
>
> > Signed-off-by: Anup Patel <anup.patel at 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.

Ok, I will use <linux/serial_reg.h>

>
>
> >  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.

Regards,
Anup