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Subject[PATCH 1/2] clk: Add support for power of two type dividers
Date
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>
---
drivers/clk/clk-divider.c | 66 ++++++++++++++++++++++++++++++++-------------
1 files changed, 47 insertions(+), 19 deletions(-)

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 8ea11b4..e548c43 100644
--- 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)
--
1.7.1


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