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, }, {} };
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, }, {}
};
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
-
Anup Patel -
Marc Zyngier