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Date: Tue, 20 Mar 2012 16:46:38 -0700
From: "Turquette, Mike" <mturquette@...com>
To: Shawn Guo <shawn.guo@...aro.org>
Cc: Paul Walmsley <paul@...an.com>,
Russell King <linux@....linux.org.uk>,
Linus Walleij <linus.walleij@...ricsson.com>,
patches@...aro.org, Magnus Damm <magnus.damm@...il.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
Stephen Boyd <sboyd@...eaurora.org>,
linux-kernel@...r.kernel.org,
Saravana Kannan <skannan@...eaurora.org>,
linaro-dev@...ts.linaro.org,
Jeremy Kerr <jeremy.kerr@...onical.com>,
Arnd Bergman <arnd.bergmann@...aro.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v7 2/3] clk: introduce the common clock framework
On Tue, Mar 20, 2012 at 7:02 AM, Shawn Guo <shawn.guo@...aro.org> wrote:
> 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.
This is something that was discussed on the list but not taken in due
to rapid flux in code. I always liked the idea however.
>
>> + 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:
This places the burden of checking the flags onto the .round_rate
implementation with __clk_get_flags, but that's not a problem really.
>
> 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
ACK
>
> 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
ACK
>
> 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)) {
This is wrong. CLK_SET_RATE_PARENT is a common clock flag applied to
struct clk's .flags member, not the divider. This function must still
use __clk_get_flags(hw->clk) here, but that's OK.
> + 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
ACK, besides my comment above.
>
> 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.
As mentioned above, you'll still need to check for CLK_SET_RATE_PARENT
in your .round_rate implementation with __clk_get_flags(hw->clk).
Did you want to send a formal patch or just have me absorb this into
the fixes I'm brewing already? I've already fixed the potential null
ptr dereferences in clk_calc_new_rates, but that's no big deal.
Regards,
Mike
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