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authorGuennadi Liakhovetski <g.liakhovetski@gmx.de>2010-11-02 11:27:24 +0000
committerPaul Mundt <lethal@linux-sh.org>2010-11-08 09:35:26 +0900
commit6af26c6c99f01e810f9944543df810e320284aa3 (patch)
tree9eaca6f86d322b700484e13cd4ebb0b3f6fc0c97 /drivers/sh/clk
parent5aefa34fada9d17a00635516688de34702451708 (diff)
downloadlinux-6af26c6c99f01e810f9944543df810e320284aa3.tar.bz2
sh: add clk_round_parent() to optimize parent clock rate
Sometimes it is possible and reasonable to adjust the parent clock rate to improve precision of the child clock, e.g., if the child clock has no siblings. clk_round_parent() is a new addition to the SH clock-framework API, that implements such an optimization for child clocks with divisors, taking all integer values in a range. Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Diffstat (limited to 'drivers/sh/clk')
-rw-r--r--drivers/sh/clk/core.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/drivers/sh/clk/core.c b/drivers/sh/clk/core.c
index 861144360d89..b3840597ad6e 100644
--- a/drivers/sh/clk/core.c
+++ b/drivers/sh/clk/core.c
@@ -541,6 +541,81 @@ long clk_round_rate(struct clk *clk, unsigned long rate)
}
EXPORT_SYMBOL_GPL(clk_round_rate);
+long clk_round_parent(struct clk *clk, unsigned long target,
+ unsigned long *best_freq, unsigned long *parent_freq,
+ unsigned int div_min, unsigned int div_max)
+{
+ struct cpufreq_frequency_table *freq, *best = NULL;
+ unsigned long error = ULONG_MAX, freq_high, freq_low, div;
+ struct clk *parent = clk_get_parent(clk);
+
+ if (!parent) {
+ *parent_freq = 0;
+ *best_freq = clk_round_rate(clk, target);
+ return abs(target - *best_freq);
+ }
+
+ for (freq = parent->freq_table; freq->frequency != CPUFREQ_TABLE_END;
+ freq++) {
+ if (freq->frequency == CPUFREQ_ENTRY_INVALID)
+ continue;
+
+ if (unlikely(freq->frequency / target <= div_min - 1)) {
+ unsigned long freq_max = (freq->frequency + div_min / 2) / div_min;
+ if (error > target - freq_max) {
+ error = target - freq_max;
+ best = freq;
+ if (best_freq)
+ *best_freq = freq_max;
+ }
+ pr_debug("too low freq %lu, error %lu\n", freq->frequency, target - freq_max);
+ if (!error)
+ break;
+ continue;
+ }
+
+ if (unlikely(freq->frequency / target >= div_max)) {
+ unsigned long freq_min = (freq->frequency + div_max / 2) / div_max;
+ if (error > freq_min - target) {
+ error = freq_min - target;
+ best = freq;
+ if (best_freq)
+ *best_freq = freq_min;
+ }
+ pr_debug("too high freq %lu, error %lu\n", freq->frequency, freq_min - target);
+ if (!error)
+ break;
+ continue;
+ }
+
+
+ div = freq->frequency / target;
+ freq_high = freq->frequency / div;
+ freq_low = freq->frequency / (div + 1);
+ if (freq_high - target < error) {
+ error = freq_high - target;
+ best = freq;
+ if (best_freq)
+ *best_freq = freq_high;
+ }
+ if (target - freq_low < error) {
+ error = target - freq_low;
+ best = freq;
+ if (best_freq)
+ *best_freq = freq_low;
+ }
+ pr_debug("%u / %lu = %lu, / %lu = %lu, best %lu, parent %u\n",
+ freq->frequency, div, freq_high, div + 1, freq_low,
+ *best_freq, best->frequency);
+ if (!error)
+ break;
+ }
+ if (parent_freq)
+ *parent_freq = best->frequency;
+ return error;
+}
+EXPORT_SYMBOL_GPL(clk_round_parent);
+
#ifdef CONFIG_PM
static int clks_sysdev_suspend(struct sys_device *dev, pm_message_t state)
{