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

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

[Anup Patel]

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>

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>
 
 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, },
 	{}
 };
 
-- 
1.7.9.5

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

[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, },
>  	{}
>  };

-- 
Fast, cheap, reliable. Pick two.

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

[Anup Patel]

On 1 March 2013 13:47, Marc Zyngier <marc.zyngier@arm.com> wrote:
>
> 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.

Sure, I will fix this.

>
>
> > 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.

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