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