ARM: 6277/1: mach-shmobile: Allow users to select HZ, default to 128

Introduce SHMOBILE_TIMER_HZ for SH-Mobile.

Allow users to select HZ on their system to
minimize potential timer drift. Use 128 Hz as
default to work well with the 32768 Hz RCLK.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 98922f7..db4f2ee 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1189,6 +1189,7 @@ config HZ
        default 200 if ARCH_EBSA110 || ARCH_S3C2410 || ARCH_S5P6440 || ARCH_S5P6442 || ARCH_S5PV210
        default OMAP_32K_TIMER_HZ if ARCH_OMAP && OMAP_32K_TIMER
        default AT91_TIMER_HZ if ARCH_AT91
+       default SHMOBILE_TIMER_HZ if ARCH_SHMOBILE
        default 100
 
 config THUMB2_KERNEL

diff --git a/arch/arm/mach-shmobile/Kconfig b/arch/arm/mach-shmobile/Kconfig
index f2b88c5..4c704b4 100644 (file)
--- a/arch/arm/mach-shmobile/Kconfig
+++ b/arch/arm/mach-shmobile/Kconfig
@@ -70,6 +70,18 @@ endmenu
 
 menu "Timer and clock configuration"
 
+config SHMOBILE_TIMER_HZ
+       int "Kernel HZ (jiffies per second)"
+       range 32 1024
+       default "128"
+       help
+         Allows the configuration of the timer frequency. It is customary
+         to have the timer interrupt run at 1000 Hz or 100 Hz, but in the
+         case of low timer frequencies other values may be more suitable.
+         SH-Mobile systems using a 32768 Hz RCLK for clock events may want
+         to select a HZ value such as 128 that can evenly divide RCLK.
+         A HZ value that does not divide evenly may cause timer drift.
+
 config SH_TIMER_CMT
        bool "CMT timer driver"
        default y