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>

2 files changed, 13 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 98922f7d2d12..db4f2ee3a750 100644
--- 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 f2b88c5fe142..4c704b4e8b34 100644
--- 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