diff options
Diffstat (limited to 'include/asm-arm/arch-ns9xxx/clock.h')
| -rw-r--r-- | include/asm-arm/arch-ns9xxx/clock.h | 34 |
1 files changed, 32 insertions, 2 deletions
diff --git a/include/asm-arm/arch-ns9xxx/clock.h b/include/asm-arm/arch-ns9xxx/clock.h index a7c5ab3d9011..bf30cbdcc2bf 100644 --- a/include/asm-arm/arch-ns9xxx/clock.h +++ b/include/asm-arm/arch-ns9xxx/clock.h @@ -11,13 +11,43 @@ #ifndef __ASM_ARCH_CLOCK_H #define __ASM_ARCH_CLOCK_H +#include <asm/arch-ns9xxx/regs-sys.h> + +#define CRYSTAL 29491200 /* Hz */ + +/* The HRM calls this value f_vco */ static inline u32 ns9xxx_systemclock(void) __attribute__((const)); static inline u32 ns9xxx_systemclock(void) { + u32 pll = SYS_PLL; + /* - * This should be a multiple of HZ * TIMERCLOCKSELECT (in time.c) + * The system clock should be a multiple of HZ * TIMERCLOCKSELECT (in + * time.c). + * + * The following values are given: + * - TIMERCLOCKSELECT == 2^i for an i in {0 .. 6} + * - CRYSTAL == 29491200 == 2^17 * 3^2 * 5^2 + * - ND in {0 .. 31} + * - FS in {0 .. 3} + * + * Assuming the worst, we consider: + * - TIMERCLOCKSELECT == 64 + * - ND == 0 + * - FS == 3 + * + * So HZ should be a divisor of: + * (CRYSTAL * (ND + 1) >> FS) / TIMERCLOCKSELECT + * == (2^17 * 3^2 * 5^2 * 1 >> 3) / 64 + * == 2^8 * 3^2 * 5^2 + * == 57600 + * + * Currently HZ is defined to be 100 for this platform. + * + * Fine. */ - return 353894400; + return CRYSTAL * (REGGET(pll, SYS_PLL, ND) + 1) + >> REGGET(pll, SYS_PLL, FS); } static inline u32 ns9xxx_cpuclock(void) __attribute__((const)); |