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    Subject[PATCH v3 2/2] ARC: Dynamically determine BASE_BAUD from DeviceTree
    Date
    This resolves the BASE_BAUD issue in Multiplatform images

    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    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>
    Cc: Peter Hurley <peter@hurleysoftware.com>
    Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
    ---
    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 <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..69a790cd9b6e 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 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;
    }
    --
    1.9.1


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