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>

1 files changed, 12 insertions, 0 deletions

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