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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>
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2 changed files with 29 additions and 18 deletions
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@ -10,26 +10,13 @@
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#define _ASM_ARC_SERIAL_H
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/*
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* early-8250 requires BASE_BAUD to be defined and includes this header.
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* We put in a typical value:
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* (core clk / 16) - i.e. UART samples 16 times per sec.
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* Athough in multi-platform-image this might not work, specially if the
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* clk driving the UART is different.
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* We can't use DeviceTree as this is typically for early serial.
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* early 8250 (now earlycon) requires BASE_BAUD to be defined in this header.
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* However to still determine it dynamically (for multi-platform images)
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* we do this in a helper by parsing the FDT early
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*/
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#include <asm/clk.h>
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extern unsigned int __init arc_early_base_baud(void);
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#define BASE_BAUD (arc_get_core_freq() / 16)
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/*
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* This is definitely going to break early 8250 consoles on multi-platform
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* images but hey, it won't add any code complexity for a debug feature of
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* one broken driver.
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*/
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#ifdef CONFIG_ARC_PLAT_TB10X
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#undef BASE_BAUD
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#define BASE_BAUD (arc_get_core_freq() / 16 / 3)
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#endif
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#define BASE_BAUD arc_early_base_baud()
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#endif /* _ASM_ARC_SERIAL_H */
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@ -17,6 +17,28 @@
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#include <asm/clk.h>
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#include <asm/mach_desc.h>
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#ifdef CONFIG_SERIAL_8250_CONSOLE
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static unsigned int __initdata arc_base_baud;
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unsigned int __init arc_early_base_baud(void)
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{
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return arc_base_baud/16;
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}
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static void __init arc_set_early_base_baud(unsigned long dt_root)
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{
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unsigned int core_clk = arc_get_core_freq();
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if (of_flat_dt_is_compatible(dt_root, "abilis,arc-tb10x"))
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arc_base_baud = core_clk/3;
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else
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arc_base_baud = core_clk;
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}
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#else
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#define arc_set_early_base_baud(dt_root)
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#endif
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static const void * __init arch_get_next_mach(const char *const **match)
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{
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static const struct machine_desc *mdesc = __arch_info_begin;
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@ -56,5 +78,7 @@ const struct machine_desc * __init setup_machine_fdt(void *dt)
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if (clk)
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arc_set_core_freq(of_read_ulong(clk, len/4));
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arc_set_early_base_baud(dt_root);
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return mdesc;
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}
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