2 files changed, 79 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)
 {
diff --git a/include/linux/sh_clk.h b/include/linux/sh_clk.h
index 4dca992f3093..cea0c38e7a63 100644
--- a/include/linux/sh_clk.h
+++ b/include/linux/sh_clk.h
@@ -122,6 +122,10 @@ int clk_rate_table_find(struct clk *clk,
 long clk_rate_div_range_round(struct clk *clk, unsigned int div_min,
                               unsigned int div_max, unsigned long 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);
+
 #define SH_CLK_MSTP32(_parent, _enable_reg, _enable_bit, _flags)        \
 {                                                                       \
         .parent         = _parent,                                      \