Commit 5248c657 authored by David Brownell's avatar David Brownell Committed by Russell King
Browse files

[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 <>
Acked-by: default avatarRemy Bhmer <>
Acked-by: default avatarAndrew Victor <>
Signed-off-by: default avatarRussell King <>
parent 156864f8
......@@ -657,6 +657,7 @@ config HZ
default 128 if ARCH_L7200
default 200 if ARCH_EBSA110 || ARCH_S3C2410
default AT91_TIMER_HZ if ARCH_AT91
default 100
config AEABI
......@@ -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"
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.
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