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Commit 5248c657 authored by David Brownell's avatar David Brownell Committed by Russell King
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[ARM] 4646/1: AT91: configurable HZ, default to 128



This makes HZ configurable on AT91, following the model used on OMAP.

It defaults to a power of two on AT91rm9200 chips, avoiding rounding
errors which come from dividing a 32 KiHz clock to generate scheduler
irqs; and uses 100 on AT91sam926x chips, using MCK/16 (multi-MHZ).

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Acked-by: default avatarRemy Bhmer <linux@bohmer.net>
Acked-by: default avatarAndrew Victor <andrew@sanpeople.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 156864f8
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+1 −0
Original line number Diff line number Diff line
@@ -657,6 +657,7 @@ config HZ
	default 128 if ARCH_L7200
	default 200 if ARCH_EBSA110 || ARCH_S3C2410
	default OMAP_32K_TIMER_HZ if ARCH_OMAP && OMAP_32K_TIMER
	default AT91_TIMER_HZ if ARCH_AT91
	default 100

config AEABI
+16 −0
Original line number Diff line number Diff line
@@ -219,6 +219,22 @@ config AT91_PROGRAMMABLE_CLOCKS
	  Select this if you need to program one or more of the PCK0..PCK3
	  programmable clock outputs.

config AT91_TIMER_HZ
       int "Kernel HZ (jiffies per second)"
       range 32 1024
       depends on ARCH_AT91
       default "128" if ARCH_AT91RM9200
       default "100"
       help
	  On AT91rm9200 chips where you're using a system clock derived
	  from the 32768 Hz hardware clock, this tick rate should divide
	  it exactly: use a power-of-two value, such as 128 or 256, to
	  reduce timing errors caused by rounding.

	  On AT91sam926x chips, or otherwise when using a higher precision
	  system clock (of at least several MHz), rounding is less of a
	  problem so it can be safer to use a decimal values like 100.

endmenu

endif