diff options
| author | Vineet Gupta <vgupta@synopsys.com> | 2014-10-28 15:04:05 +0530 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2015-02-02 17:08:37 +0530 |
| commit | ffb7fcd66f14bc716b9fdf559e71909131fef39b (patch) | |
| tree | 35b7c289c75651d8244ac0e7d7ede0185da1f367 /arch/arc | |
| parent | 7bf6df575fd628fd7ec737789ae8bcb7081d77de (diff) | |
| download | linux-ffb7fcd66f14bc716b9fdf559e71909131fef39b.tar.bz2 | |
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 <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Rob Herring <robh@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
| -rw-r--r-- | arch/arc/include/asm/serial.h | 23 | ||||
| -rw-r--r-- | 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 <asm/clk.h> +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 <asm/clk.h> #include <asm/mach_desc.h> +#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; } |