Spread-spectrum clock adjust support The ixp4xx can be driven from a 2% down spread-spectrum clock. Doing so however will cause your UART timing and system clock timing to be 2% slow. This patch adds a kernel built-time configuration to adjust those clocks so that running on boards with a spread-spectrum clock do not show clock drift or UART issues.
Signed-off-by: Tim Harvey <thar...@gateworks.com> target/linux/ixp4xx/config-3.3 | 1 target/linux/ixp4xx/patches-3.3/700-spread-spectrum-adjust.patch | 45 ++++++++++ 2 files changed, 46 insertions(+) Index: trunk/target/linux/ixp4xx/patches-3.3/700-spread-spectrum-adjust.patch =================================================================== --- trunk/target/linux/ixp4xx/patches-3.3/700-spread-spectrum-adjust.patch (revision 0) +++ trunk/target/linux/ixp4xx/patches-3.3/700-spread-spectrum-adjust.patch (working copy) @@ -0,0 +1,45 @@ +--- a/arch/arm/mach-ixp4xx/Kconfig ++++ b/arch/arm/mach-ixp4xx/Kconfig +@@ -296,6 +296,12 @@ config MACH_MI424WR + + comment "IXP4xx Options" + ++config IXP4XX_SPREAD_SPECTRUM_CLK ++ bool "Adjust clocks for 2% Down Spread Spectrum source" ++ help ++ Say 'Y' here if you want your kernel to adjust clocks for a ++ 2% down spread-spectrum oscillator used as the CPU clock. ++ + config IXP4XX_INDIRECT_PCI + bool "Use indirect PCI memory access" + depends on PCI +--- a/arch/arm/mach-ixp4xx/include/mach/platform.h ++++ b/arch/arm/mach-ixp4xx/include/mach/platform.h +@@ -73,7 +73,12 @@ extern unsigned long ixp4xx_exp_bus_size + * Clock Speed Definitions. + */ + #define IXP4XX_PERIPHERAL_BUS_CLOCK (66) /* 66Mhzi APB BUS */ ++#ifdef CONFIG_IXP4XX_SPREAD_SPECTRUM_CLK ++// Adjusted for 2% down spread-spectrum osciallator ++#define IXP4XX_UART_XTAL 14598144 ++#else + #define IXP4XX_UART_XTAL 14745600 ++#endif + + /* + * This structure provide a means for the board setup code +--- a/arch/arm/mach-ixp4xx/include/mach/timex.h ++++ b/arch/arm/mach-ixp4xx/include/mach/timex.h +@@ -10,7 +10,12 @@ + * 66.66... MHz. We do a convulted calculation of CLOCK_TICK_RATE b/c the + * timer register ignores the bottom 2 bits of the LATCH value. + */ ++#ifdef CONFIG_IXP4XX_SPREAD_SPECTRUM_CLK ++// Adjusted for 2% down spread-spectrum osciallator ++#define IXP4XX_TIMER_FREQ 65999340 ++#else + #define IXP4XX_TIMER_FREQ 66666000 ++#endif + #define CLOCK_TICK_RATE \ + (((IXP4XX_TIMER_FREQ / HZ & ~IXP4XX_OST_RELOAD_MASK) + 1) * HZ) + Index: trunk/target/linux/ixp4xx/config-3.3 =================================================================== --- trunk/target/linux/ixp4xx/config-3.3 (revision 33620) +++ trunk/target/linux/ixp4xx/config-3.3 (working copy) @@ -109,6 +109,7 @@ # CONFIG_IXP4XX_INDIRECT_PCI is not set CONFIG_IXP4XX_NPE=y CONFIG_IXP4XX_QMGR=y +# CONFIG_IXP4XX_SPREAD_SPECTRUM_CLK is not set CONFIG_IXP4XX_WATCHDOG=y CONFIG_KTIME_SCALAR=y CONFIG_LEDS_FSG=y _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
