[ARM] 4646/1: AT91: configurable HZ, default to 128 (5248c657) · Commits · 戴 / test

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:

David Brownell <dbrownell@users.sourceforge.net> Acked-by:

Remy Bhmer <linux@bohmer.net> Acked-by:

Andrew Victor <andrew@sanpeople.com> Signed-off-by:

Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

+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

arch/arm/mach-at91/Kconfig

+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

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