From mboxrd@z Thu Jan 1 00:00:00 1970 From: anup.patel@linaro.org (Anup Patel) Date: Fri, 1 Mar 2013 14:11:47 +0530 Subject: [PATCH V2] arm64: add support for 8250/16550 earlyprintk Message-ID: <1362127307-7986-1-git-send-email-anup.patel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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, Kernel args for 32-bit aligned regs: earlyprintk=uart8250-32bit, Signed-off-by: Anup Patel --- 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..c39e90b 100644 --- a/arch/arm64/kernel/early_printk.c +++ b/arch/arm64/kernel/early_printk.c @@ -24,11 +24,32 @@ #include #include +#include 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