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Diffstat (limited to 'arch/v850/kernel/v850e_utils.c')
-rw-r--r--arch/v850/kernel/v850e_utils.c62
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diff --git a/arch/v850/kernel/v850e_utils.c b/arch/v850/kernel/v850e_utils.c
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+/*
+ * include/asm-v850/v850e_utils.h -- Utility functions associated with
+ * V850E CPUs
+ *
+ * Copyright (C) 2001,02,03 NEC Electronics Corporation
+ * Copyright (C) 2001,02,03 Miles Bader <miles@gnu.org>
+ *
+ * This file is subject to the terms and conditions of the GNU General
+ * Public License. See the file COPYING in the main directory of this
+ * archive for more details.
+ *
+ * Written by Miles Bader <miles@gnu.org>
+ */
+
+#include <asm/v850e_utils.h>
+
+/* Calculate counter clock-divider and count values to attain the
+ desired frequency RATE from the base frequency BASE_FREQ. The
+ counter is expected to have a clock-divider, which can divide the
+ system cpu clock by a power of two value from MIN_DIVLOG2 to
+ MAX_DIV_LOG2, and a word-size of COUNTER_SIZE bits (the counter
+ counts up and resets whenever it's equal to the compare register,
+ generating an interrupt or whatever when it does so). The returned
+ values are: *DIVLOG2 -- log2 of the desired clock divider and *COUNT
+ -- the counter compare value to use. Returns true if it was possible
+ to find a reasonable value, otherwise false (and the other return
+ values will be set to be as good as possible). */
+int calc_counter_params (unsigned long base_freq,
+ unsigned long rate,
+ unsigned min_divlog2, unsigned max_divlog2,
+ unsigned counter_size,
+ unsigned *divlog2, unsigned *count)
+{
+ unsigned _divlog2;
+ int ok = 0;
+
+ /* Find the lowest clock divider setting that can represent RATE. */
+ for (_divlog2 = min_divlog2; _divlog2 <= max_divlog2; _divlog2++) {
+ /* Minimum interrupt rate possible using this divider. */
+ unsigned min_int_rate
+ = (base_freq >> _divlog2) >> counter_size;
+
+ if (min_int_rate <= rate) {
+ /* This setting is the highest resolution
+ setting that's slow enough enough to attain
+ RATE interrupts per second, so use it. */
+ ok = 1;
+ break;
+ }
+ }
+
+ if (_divlog2 > max_divlog2)
+ /* Can't find correct setting. */
+ _divlog2 = max_divlog2;
+
+ if (divlog2)
+ *divlog2 = _divlog2;
+ if (count)
+ *count = ((base_freq >> _divlog2) + rate/2) / rate;
+
+ return ok;
+}