clk: Add support for power of two type dividers

Quite often dividers and the value programmed in the
register have a relation of 'power of two', something like
value	div
0	1
1	2
2	4
3	8...

Add support for such dividers as part of clk-divider.

The clk-divider flag 'CLK_DIVIDER_POWER_OF_TWO' should be used
to define such clocks.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 8ea11b4..e548c43 100644 (file)
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -30,18 +30,50 @@
 #define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
 
 #define div_mask(d)    ((1 << (d->width)) - 1)
+#define is_power_of_two(i)     !(i & ~i)
+
+static unsigned int _get_maxdiv(struct clk_divider *divider)
+{
+       if (divider->flags & CLK_DIVIDER_ONE_BASED)
+               return div_mask(divider);
+       if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+               return 1 << div_mask(divider);
+       return div_mask(divider) + 1;
+}
+
+static unsigned int _get_div(struct clk_divider *divider, unsigned int val)
+{
+       if (divider->flags & CLK_DIVIDER_ONE_BASED)
+               return val;
+       if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+               return 1 << val;
+       return val + 1;
+}
+
+static unsigned int _get_val(struct clk_divider *divider, u8 div)
+{
+       if (divider->flags & CLK_DIVIDER_ONE_BASED)
+               return div;
+       if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+               return __ffs(div);
+       return div - 1;
+}
 
 static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
                unsigned long parent_rate)
 {
        struct clk_divider *divider = to_clk_divider(hw);
-       unsigned int div;
+       unsigned int div, val;
 
-       div = readl(divider->reg) >> divider->shift;
-       div &= div_mask(divider);
+       val = readl(divider->reg) >> divider->shift;
+       val &= div_mask(divider);
 
-       if (!(divider->flags & CLK_DIVIDER_ONE_BASED))
-               div++;
+       div = _get_div(divider, val);
+       if (!div) {
+               WARN(1, "%s: Invalid divisor for clock %s\n", __func__,
+                                               __clk_get_name(hw->clk));
+               return parent_rate;
+       }
 
        return parent_rate / div;
 }
@@ -62,10 +94,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
        if (!rate)
                rate = 1;
 
-       maxdiv = (1 << divider->width);
-
-       if (divider->flags & CLK_DIVIDER_ONE_BASED)
-               maxdiv--;
+       maxdiv = _get_maxdiv(divider);
 
        if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
                parent_rate = *best_parent_rate;
@@ -82,6 +111,9 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
        maxdiv = min(ULONG_MAX / rate, maxdiv);
 
        for (i = 1; i <= maxdiv; i++) {
+               if ((divider->flags & CLK_DIVIDER_POWER_OF_TWO)
+                       && (!is_power_of_two(i)))
+                       continue;
                parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
                                MULT_ROUND_UP(rate, i));
                now = parent_rate / i;
@@ -93,9 +125,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
        }
 
        if (!bestdiv) {
-               bestdiv = (1 << divider->width);
-               if (divider->flags & CLK_DIVIDER_ONE_BASED)
-                       bestdiv--;
+               bestdiv = _get_maxdiv(divider);
                *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
        }
 
@@ -115,24 +145,22 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long parent_rate)
 {
        struct clk_divider *divider = to_clk_divider(hw);
-       unsigned int div;
+       unsigned int div, value;
        unsigned long flags = 0;
        u32 val;
 
        div = parent_rate / rate;
+       value = _get_val(divider, div);
 
-       if (!(divider->flags & CLK_DIVIDER_ONE_BASED))
-               div--;
-
-       if (div > div_mask(divider))
-               div = div_mask(divider);
+       if (value > div_mask(divider))
+               value = div_mask(divider);
 
        if (divider->lock)
                spin_lock_irqsave(divider->lock, flags);
 
        val = readl(divider->reg);
        val &= ~(div_mask(divider) << divider->shift);
-       val |= div << divider->shift;
+       val |= value << divider->shift;
        writel(val, divider->reg);
 
        if (divider->lock)