From ffb7fcd66f14bc716b9fdf559e71909131fef39b Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Tue, 28 Oct 2014 15:04:05 +0530 Subject: [PATCH] ARC: Dynamically determine BASE_BAUD from DeviceTree 8250 earlycon is broken on multi-platform ARC because the UART clk value (BASE_BAUD) is fixed at build time. Instead, determine the appropriate UART clk at runtime; parse the devicetree early for platforms requiring alternate UART clk values (currently only the TB10X platform). Cc: Jiri Slaby Cc: linux-serial@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Rob Herring Cc: Arnd Bergmann Reviewed-by: Peter Hurley Acked-by: Greg Kroah-Hartman Signed-off-by: Vineet Gupta --- arch/arc/include/asm/serial.h | 23 +++++------------------ arch/arc/kernel/devtree.c | 24 ++++++++++++++++++++++++ 2 files changed, 29 insertions(+), 18 deletions(-) diff --git a/arch/arc/include/asm/serial.h b/arch/arc/include/asm/serial.h index 602b0970a764..744a6ae15754 100644 --- a/arch/arc/include/asm/serial.h +++ b/arch/arc/include/asm/serial.h @@ -10,26 +10,13 @@ #define _ASM_ARC_SERIAL_H /* - * early-8250 requires BASE_BAUD to be defined and includes this header. - * We put in a typical value: - * (core clk / 16) - i.e. UART samples 16 times per sec. - * Athough in multi-platform-image this might not work, specially if the - * clk driving the UART is different. - * We can't use DeviceTree as this is typically for early serial. + * early 8250 (now earlycon) requires BASE_BAUD to be defined in this header. + * However to still determine it dynamically (for multi-platform images) + * we do this in a helper by parsing the FDT early */ -#include +extern unsigned int __init arc_early_base_baud(void); -#define BASE_BAUD (arc_get_core_freq() / 16) - -/* - * This is definitely going to break early 8250 consoles on multi-platform - * images but hey, it won't add any code complexity for a debug feature of - * one broken driver. - */ -#ifdef CONFIG_ARC_PLAT_TB10X -#undef BASE_BAUD -#define BASE_BAUD (arc_get_core_freq() / 16 / 3) -#endif +#define BASE_BAUD arc_early_base_baud() #endif /* _ASM_ARC_SERIAL_H */ diff --git a/arch/arc/kernel/devtree.c b/arch/arc/kernel/devtree.c index fffdb5e41b20..5036d4c06996 100644 --- a/arch/arc/kernel/devtree.c +++ b/arch/arc/kernel/devtree.c @@ -17,6 +17,28 @@ #include #include +#ifdef CONFIG_SERIAL_8250_CONSOLE + +static unsigned int __initdata arc_base_baud; + +unsigned int __init arc_early_base_baud(void) +{ + return arc_base_baud/16; +} + +static void __init arc_set_early_base_baud(unsigned long dt_root) +{ + unsigned int core_clk = arc_get_core_freq(); + + if (of_flat_dt_is_compatible(dt_root, "abilis,arc-tb10x")) + arc_base_baud = core_clk/3; + else + arc_base_baud = core_clk; +} +#else +#define arc_set_early_base_baud(dt_root) +#endif + static const void * __init arch_get_next_mach(const char *const **match) { static const struct machine_desc *mdesc = __arch_info_begin; @@ -56,5 +78,7 @@ const struct machine_desc * __init setup_machine_fdt(void *dt) if (clk) arc_set_core_freq(of_read_ulong(clk, len/4)); + arc_set_early_base_baud(dt_root); + return mdesc; }