diff options
| author | Anup Patel <anup.patel@linaro.org> | 2013-03-01 08:41:47 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2013-03-20 16:46:42 +0000 |
| commit | e53f2f4b570d85c7208dfc97de54db1296b88207 (patch) | |
| tree | 290aecfb7ef4dad6cf30bcc8c3f920c448e81c98 /arch/arm64 | |
| parent | 0492f72508184d451101564e235b0c32edf9acd3 (diff) | |
arm64: add support for 8250/16550 earlyprintk
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=uart8250-32bit,<phys_address>
Signed-off-by: Anup Patel <anup.patel@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/kernel/early_printk.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c index 0bb7436c57dc..ac974f48a7a2 100644 --- a/arch/arm64/kernel/early_printk.c +++ b/arch/arm64/kernel/early_printk.c @@ -24,6 +24,7 @@ #include <linux/io.h> #include <linux/amba/serial.h> +#include <linux/serial_reg.h> static void __iomem *early_base; static void (*printch)(char ch); @@ -51,6 +52,26 @@ static void smh_printch(char ch) : : "r" (&ch) : "x0", "x1", "memory"); } +/* + * 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)); +} + struct earlycon_match { const char *name; void (*printch)(char ch); @@ -59,6 +80,8 @@ struct earlycon_match { static const struct earlycon_match earlycon_match[] __initconst = { { .name = "pl011", .printch = pl011_printch, }, { .name = "smh", .printch = smh_printch, }, + { .name = "uart8250-8bit", .printch = uart8250_8bit_printch, }, + { .name = "uart8250-32bit", .printch = uart8250_32bit_printch, }, {} }; |