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SubjectRe: [PATCH v7 2/3] clk: introduce the common clock framework
On Thu, Mar 15, 2012 at 11:11:19PM -0700, Mike Turquette wrote:
...
> +struct clk_ops {
> + int (*prepare)(struct clk_hw *hw);
> + void (*unprepare)(struct clk_hw *hw);
> + int (*enable)(struct clk_hw *hw);
> + void (*disable)(struct clk_hw *hw);
> + int (*is_enabled)(struct clk_hw *hw);
> + unsigned long (*recalc_rate)(struct clk_hw *hw,
> + unsigned long parent_rate);

I believe I have heard people love the interface with parent_rate
passed in. I love that too. But I would like to ask the same thing
on .round_rate and .set_rate as well for the same reason why we have
it for .recalc_rate.

> + long (*round_rate)(struct clk_hw *hw, unsigned long,
> + unsigned long *);

Yes, we already have parent_rate passed in .round_rate with an pointer.
But I think it'd be better to have it passed in no matter flag
CLK_SET_RATE_PARENT is set or not. Something like:

8<---
@@ -584,7 +584,7 @@ EXPORT_SYMBOL_GPL(clk_get_rate);
*/
unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
{
- unsigned long unused;
+ unsigned long parent_rate = 0;

if (!clk)
return -EINVAL;
@@ -592,10 +592,10 @@ unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
if (!clk->ops->round_rate)
return clk->rate;

- if (clk->flags & CLK_SET_RATE_PARENT)
- return clk->ops->round_rate(clk->hw, rate, &unused);
- else
- return clk->ops->round_rate(clk->hw, rate, NULL);
+ if (clk->parent)
+ parent_rate = clk->parent->rate;
+
+ return clk->ops->round_rate(clk->hw, rate, &parent_rate);
}

/**
@@ -765,9 +765,12 @@ static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
{
struct clk *top = clk;
- unsigned long best_parent_rate = clk->parent->rate;
+ unsigned long best_parent_rate = 0;
unsigned long new_rate;

+ if (clk->parent)
+ best_parent_rate = clk->parent->rate;
+
if (!clk->ops->round_rate && !(clk->flags & CLK_SET_RATE_PARENT)) {
clk->new_rate = clk->rate;
return NULL;
@@ -780,10 +783,7 @@ static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
goto out;
}

- if (clk->flags & CLK_SET_RATE_PARENT)
- new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
- else
- new_rate = clk->ops->round_rate(clk->hw, rate, NULL);
+ new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);

if (best_parent_rate != clk->parent->rate) {
top = clk_calc_new_rates(clk->parent, best_parent_rate);
--->8
The reason behind the change is that any clk implements .round_rate will
mostly need to get the parent rate, no matter flag CLK_SET_RATE_PARENT
is set or not. Instead of expecting every .round_rate implementation
to get the parent rate in the way beloe

parent_rate = __clk_get_rate(__clk_get_parent(hw->clk));

we can just pass the parent rate into .round_rate.

> + int (*set_parent)(struct clk_hw *hw, u8 index);
> + u8 (*get_parent)(struct clk_hw *hw);
> + int (*set_rate)(struct clk_hw *hw, unsigned long);

For the same reason, I would change .set_rate interface like below.

8<---

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index d5ac6a7..6bd8037 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -119,7 +119,8 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
}
EXPORT_SYMBOL_GPL(clk_divider_round_rate);

-static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate)
+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;
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index dbc310a..d74ac4b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -833,17 +833,18 @@ static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long even
static void clk_change_rate(struct clk *clk)
{
struct clk *child;
- unsigned long old_rate;
+ unsigned long old_rate, parent_rate = 0;
struct hlist_node *tmp;

old_rate = clk->rate;
+ if (clk->parent)
+ parent_rate = clk->parent->rate;

if (clk->ops->set_rate)
- clk->ops->set_rate(clk->hw, clk->new_rate);
+ clk->ops->set_rate(clk->hw, clk->new_rate, parent_rate);

if (clk->ops->recalc_rate)
- clk->rate = clk->ops->recalc_rate(clk->hw,
- clk->parent->rate);
+ clk->rate = clk->ops->recalc_rate(clk->hw, parent_rate);
else
clk->rate = clk->parent->rate;

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 5508897..1031f1f 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -125,7 +125,8 @@ struct clk_ops {
unsigned long *);
int (*set_parent)(struct clk_hw *hw, u8 index);
u8 (*get_parent)(struct clk_hw *hw);
- int (*set_rate)(struct clk_hw *hw, unsigned long);
+ int (*set_rate)(struct clk_hw *hw, unsigned long,
+ unsigned long);
void (*init)(struct clk_hw *hw);
};

--->8
Then with parent rate passed into .round_rate and .set_rate like what
we do with .recalc_rate right now, we can save particular clk
implementation from calling __clk_get_parent() and __clk_get_rate to
get parent rate.

For example, the following will the be diff we gain on clk-divider.

8<---

diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
index 6bd8037..8a28ffb 100644
--- a/drivers/clk/clk-divider.c
+++ b/drivers/clk/clk-divider.c
@@ -68,8 +68,8 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
if (divider->flags & CLK_DIVIDER_ONE_BASED)
maxdiv--;

- if (!best_parent_rate) {
- parent_rate = __clk_get_rate(__clk_get_parent(hw->clk));
+ if (!(divider->flags & CLK_SET_RATE_PARENT)) {
+ parent_rate = *best_parent_rate;
bestdiv = DIV_ROUND_UP(parent_rate, rate);
bestdiv = bestdiv == 0 ? 1 : bestdiv;
bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
@@ -109,13 +109,7 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
int div;
div = clk_divider_bestdiv(hw, rate, prate);

- if (prate)
- return *prate / div;
- else {
- unsigned long r;
- r = __clk_get_rate(__clk_get_parent(hw->clk));
- return r / div;
- }
+ return *prate / div;
}
EXPORT_SYMBOL_GPL(clk_divider_round_rate);

@@ -127,7 +121,7 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long flags = 0;
u32 val;

- div = __clk_get_rate(__clk_get_parent(hw->clk)) / rate;
+ div = parent_rate / rate;

if (!(divider->flags & CLK_DIVIDER_ONE_BASED))
div--;
--->8
I always get a sense of worry in using functions named in __xxx which
sounds like something somehow internal. With the requested interface
change above, I can get all __xxx functions out of my clk_ops
implementation.

> + void (*init)(struct clk_hw *hw);
> +};

--
Regards,
Shawn


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