[PATCH 0/4] clk: Provide option to unprepare unused clocks at late init

[PATCH 0/4] clk: Provide option to unprepare unused clocks at late init

[Ulf Hansson]

From: Ulf Hansson <ulf.hansson@linaro.org>

The disable_unused sequence executed at late init, is already handling the
fast unused ungated clocks to be gated. This patchset extends this sequence to
include the slow unused prepared clocks to be unprepared.

The default behavior will not change in this patchset. To unprepare unused
clocks during the disable_unused sequence, the clk_hw needs to implement
the new optional callback, is_prepared.

The motivation for this patchset is to save power. Clocks that is from
bootloaders prepared|enabled, but not used should be unprepared|disabled.

Patch 4 is specific for ux500, which implements the is_prepared callback
for it's PRMCU clocks.

Note that patch 1-3 has been sent earlier, but since a proof of concept
patch could be useful, as patch 4 is, the hole patchset is resent.

Ulf Hansson (4):
  clk: Introduce optional is_prepared callback
  clk: Unprepare the unused prepared slow clocks at late init
  clk: Introduce optional unprepare_unused callback
  clk: ux500: Support is_prepared callback for clk-prcmu

 drivers/clk/clk.c             |   53 ++++++++++++++++
 drivers/clk/ux500/clk-prcmu.c |  134 ++++++++++++++++++++++++-----------------
 include/linux/clk-provider.h  |   11 ++++
 3 files changed, 144 insertions(+), 54 deletions(-)

-- 
1.7.10

[PATCH 1/4] clk: Introduce optional is_prepared callback

[Ulf Hansson]

From: Ulf Hansson <ulf.hansson@linaro.org>

To reflect whether a clk_hw is prepared the clk_hw may implement
the optional is_prepared callback. If not implemented we fall back
to use the software prepare counter.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/clk/clk.c            |   21 +++++++++++++++++++++
 include/linux/clk-provider.h |    6 ++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 593a2e4..deb259a 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -458,6 +458,27 @@ unsigned long __clk_get_flags(struct clk *clk)
 	return !clk ? 0 : clk->flags;
 }
 
+bool __clk_is_prepared(struct clk *clk)
+{
+	int ret;
+
+	if (!clk)
+		return false;
+
+	/*
+	 * .is_prepared is optional for clocks that can prepare
+	 * fall back to software usage counter if it is missing
+	 */
+	if (!clk->ops->is_prepared) {
+		ret = clk->prepare_count ? 1 : 0;
+		goto out;
+	}
+
+	ret = clk->ops->is_prepared(clk->hw);
+out:
+	return !!ret;
+}
+
 bool __clk_is_enabled(struct clk *clk)
 {
 	int ret;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 4989b8a..86ff6be 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -45,6 +45,10 @@ struct clk_hw;
  * 		undo any work done in the @prepare callback. Called with
  * 		prepare_lock held.
  *
+ * @is_prepared: Queries the hardware to determine if the clock is prepared.
+ *		This function is allowed to sleep. Optional, if this op is not
+ *		set then the prepare count will be used.
+ *
  * @enable:	Enable the clock atomically. This must not return until the
  * 		clock is generating a valid clock signal, usable by consumer
  * 		devices. Called with enable_lock held. This function must not
@@ -108,6 +112,7 @@ struct clk_hw;
 struct clk_ops {
 	int		(*prepare)(struct clk_hw *hw);
 	void		(*unprepare)(struct clk_hw *hw);
+	int		(*is_prepared)(struct clk_hw *hw);
 	int		(*enable)(struct clk_hw *hw);
 	void		(*disable)(struct clk_hw *hw);
 	int		(*is_enabled)(struct clk_hw *hw);
@@ -351,6 +356,7 @@ unsigned int __clk_get_enable_count(struct clk *clk);
 unsigned int __clk_get_prepare_count(struct clk *clk);
 unsigned long __clk_get_rate(struct clk *clk);
 unsigned long __clk_get_flags(struct clk *clk);
+bool __clk_is_prepared(struct clk *clk);
 bool __clk_is_enabled(struct clk *clk);
 struct clk *__clk_lookup(const char *name);
 
-- 
1.7.10

[PATCH 2/4] clk: Unprepare the unused prepared slow clocks at late init

[Ulf Hansson]

From: Ulf Hansson <ulf.hansson@linaro.org>

The unused ungated fast clocks are already being disabled from
clk_disable_unused at late init. This patch extend this sequence
to the slow unused prepared clocks to be unprepared.

Unless the optional .is_prepared callback is implemented by a
clk_hw the clk_disable_unused sequence will not unprepare any
unused clocks, since it will fall back to use the software
prepare counter.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/clk/clk.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index deb259a..0944348 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -341,6 +341,29 @@ static inline int clk_debug_register(struct clk *clk) { return 0; }
 #endif
 
 /* caller must hold prepare_lock */
+static void clk_unprepare_unused_subtree(struct clk *clk)
+{
+	struct clk *child;
+	struct hlist_node *tmp;
+
+	if (!clk)
+		return;
+
+	hlist_for_each_entry(child, tmp, &clk->children, child_node)
+		clk_unprepare_unused_subtree(child);
+
+	if (clk->prepare_count)
+		return;
+
+	if (clk->flags & CLK_IGNORE_UNUSED)
+		return;
+
+	if (__clk_is_prepared(clk))
+		if (clk->ops->unprepare)
+			clk->ops->unprepare(clk->hw);
+}
+
+/* caller must hold prepare_lock */
 static void clk_disable_unused_subtree(struct clk *clk)
 {
 	struct clk *child;
@@ -393,6 +416,12 @@ static int clk_disable_unused(void)
 	hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
 		clk_disable_unused_subtree(clk);
 
+	hlist_for_each_entry(clk, tmp, &clk_root_list, child_node)
+		clk_unprepare_unused_subtree(clk);
+
+	hlist_for_each_entry(clk, tmp, &clk_orphan_list, child_node)
+		clk_unprepare_unused_subtree(clk);
+
 	mutex_unlock(&prepare_lock);
 
 	return 0;
-- 
1.7.10

[PATCH 3/4] clk: Introduce optional unprepare_unused callback

[Ulf Hansson]

From: Ulf Hansson <ulf.hansson@linaro.org>

An unprepare_unused callback is introduced due to the same reasons to
why the disable_unused callback was added.

During the clk_disable_unused sequence, those clk_hw that needs specific
treatment with regards to being unprepared, shall implement the
unprepare_unused callback.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/clk/clk.c            |    7 +++++--
 include/linux/clk-provider.h |    5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 0944348..d8dc6d7c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -358,9 +358,12 @@ static void clk_unprepare_unused_subtree(struct clk *clk)
 	if (clk->flags & CLK_IGNORE_UNUSED)
 		return;
 
-	if (__clk_is_prepared(clk))
-		if (clk->ops->unprepare)
+	if (__clk_is_prepared(clk)) {
+		if (clk->ops->unprepare_unused)
+			clk->ops->unprepare_unused(clk->hw);
+		else if (clk->ops->unprepare)
 			clk->ops->unprepare(clk->hw);
+	}
 }
 
 /* caller must hold prepare_lock */
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 86ff6be..9e97fb4 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -49,6 +49,10 @@ struct clk_hw;
  *		This function is allowed to sleep. Optional, if this op is not
  *		set then the prepare count will be used.
  *
+ * @unprepare_unused: Unprepare the clock atomically.  Only called from
+ *		clk_disable_unused for prepare clocks with special needs.
+ *		Called with prepare mutex held. This function may sleep.
+ *
  * @enable:	Enable the clock atomically. This must not return until the
  * 		clock is generating a valid clock signal, usable by consumer
  * 		devices. Called with enable_lock held. This function must not
@@ -113,6 +117,7 @@ struct clk_ops {
 	int		(*prepare)(struct clk_hw *hw);
 	void		(*unprepare)(struct clk_hw *hw);
 	int		(*is_prepared)(struct clk_hw *hw);
+	void		(*unprepare_unused)(struct clk_hw *hw);
 	int		(*enable)(struct clk_hw *hw);
 	void		(*disable)(struct clk_hw *hw);
 	int		(*is_enabled)(struct clk_hw *hw);
-- 
1.7.10

[PATCH 4/4] clk: ux500: Support is_prepared callback for clk-prcmu

[Ulf Hansson]

From: Ulf Hansson <ulf.hansson@linaro.org>

To be able to gate unused prcmu clocks from the clk_disable_unused sequence,
clk-prcmu now implements the is_prepared callback.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/clk/ux500/clk-prcmu.c |  134 ++++++++++++++++++++++++-----------------
 1 file changed, 80 insertions(+), 54 deletions(-)

diff --git a/drivers/clk/ux500/clk-prcmu.c b/drivers/clk/ux500/clk-prcmu.c
index 74faa7e..9d83256 100644
--- a/drivers/clk/ux500/clk-prcmu.c
+++ b/drivers/clk/ux500/clk-prcmu.c
@@ -20,15 +20,23 @@
 struct clk_prcmu {
 	struct clk_hw hw;
 	u8 cg_sel;
+	int is_prepared;
 	int is_enabled;
+	int opp_requested;
 };
 
 /* PRCMU clock operations. */
 
 static int clk_prcmu_prepare(struct clk_hw *hw)
 {
+	int ret;
 	struct clk_prcmu *clk = to_clk_prcmu(hw);
-	return prcmu_request_clock(clk->cg_sel, true);
+
+	ret = prcmu_request_clock(clk->cg_sel, true);
+	if (!ret)
+		clk->is_prepared = 1;
+
+	return ret;;
 }
 
 static void clk_prcmu_unprepare(struct clk_hw *hw)
@@ -37,6 +45,14 @@ static void clk_prcmu_unprepare(struct clk_hw *hw)
 	if (prcmu_request_clock(clk->cg_sel, false))
 		pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
 			hw->init->name);
+	else
+		clk->is_prepared = 0;
+}
+
+static int clk_prcmu_is_prepared(struct clk_hw *hw)
+{
+	struct clk_prcmu *clk = to_clk_prcmu(hw);
+	return clk->is_prepared;
 }
 
 static int clk_prcmu_enable(struct clk_hw *hw)
@@ -79,58 +95,52 @@ static int clk_prcmu_set_rate(struct clk_hw *hw, unsigned long rate,
 	return prcmu_set_clock_rate(clk->cg_sel, rate);
 }
 
-static int request_ape_opp100(bool enable)
-{
-	static int reqs;
-	int err = 0;
-
-	if (enable) {
-		if (!reqs)
-			err = prcmu_qos_add_requirement(PRCMU_QOS_APE_OPP,
-							"clock", 100);
-		if (!err)
-			reqs++;
-	} else {
-		reqs--;
-		if (!reqs)
-			prcmu_qos_remove_requirement(PRCMU_QOS_APE_OPP,
-						"clock");
-	}
-	return err;
-}
-
 static int clk_prcmu_opp_prepare(struct clk_hw *hw)
 {
 	int err;
 	struct clk_prcmu *clk = to_clk_prcmu(hw);
 
-	err = request_ape_opp100(true);
-	if (err) {
-		pr_err("clk_prcmu: %s failed to request APE OPP100 for %s.\n",
-			__func__, hw->init->name);
-		return err;
+	if (!clk->opp_requested) {
+		err = prcmu_qos_add_requirement(PRCMU_QOS_APE_OPP,
+						(char *)__clk_get_name(hw->clk),
+						100);
+		if (err) {
+			pr_err("clk_prcmu: %s fail req APE OPP for %s.\n",
+				__func__, hw->init->name);
+			return err;
+		}
+		clk->opp_requested = 1;
 	}
 
 	err = prcmu_request_clock(clk->cg_sel, true);
-	if (err)
-		request_ape_opp100(false);
+	if (err) {
+		prcmu_qos_remove_requirement(PRCMU_QOS_APE_OPP,
+					(char *)__clk_get_name(hw->clk));
+		clk->opp_requested = 0;
+		return err;
+	}
 
-	return err;
+	clk->is_prepared = 1;
+	return 0;
 }
 
 static void clk_prcmu_opp_unprepare(struct clk_hw *hw)
 {
 	struct clk_prcmu *clk = to_clk_prcmu(hw);
 
-	if (prcmu_request_clock(clk->cg_sel, false))
-		goto out_error;
-	if (request_ape_opp100(false))
-		goto out_error;
-	return;
-
-out_error:
-	pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
-		hw->init->name);
+	if (prcmu_request_clock(clk->cg_sel, false)) {
+		pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
+			hw->init->name);
+		return;
+	}
+
+	if (clk->opp_requested) {
+		prcmu_qos_remove_requirement(PRCMU_QOS_APE_OPP,
+					(char *)__clk_get_name(hw->clk));
+		clk->opp_requested = 0;
+	}
+
+	clk->is_prepared = 0;
 }
 
 static int clk_prcmu_opp_volt_prepare(struct clk_hw *hw)
@@ -138,38 +148,49 @@ static int clk_prcmu_opp_volt_prepare(struct clk_hw *hw)
 	int err;
 	struct clk_prcmu *clk = to_clk_prcmu(hw);
 
-	err = prcmu_request_ape_opp_100_voltage(true);
-	if (err) {
-		pr_err("clk_prcmu: %s failed to request APE OPP VOLT for %s.\n",
-			__func__, hw->init->name);
-		return err;
+	if (!clk->opp_requested) {
+		err = prcmu_request_ape_opp_100_voltage(true);
+		if (err) {
+			pr_err("clk_prcmu: %s fail req APE OPP VOLT for %s.\n",
+				__func__, hw->init->name);
+			return err;
+		}
+		clk->opp_requested = 1;
 	}
 
 	err = prcmu_request_clock(clk->cg_sel, true);
-	if (err)
+	if (err) {
 		prcmu_request_ape_opp_100_voltage(false);
+		clk->opp_requested = 0;
+		return err;
+	}
 
-	return err;
+	clk->is_prepared = 1;
+	return 0;
 }
 
 static void clk_prcmu_opp_volt_unprepare(struct clk_hw *hw)
 {
 	struct clk_prcmu *clk = to_clk_prcmu(hw);
 
-	if (prcmu_request_clock(clk->cg_sel, false))
-		goto out_error;
-	if (prcmu_request_ape_opp_100_voltage(false))
-		goto out_error;
-	return;
-
-out_error:
-	pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
-		hw->init->name);
+	if (prcmu_request_clock(clk->cg_sel, false)) {
+		pr_err("clk_prcmu: %s failed to disable %s.\n", __func__,
+			hw->init->name);
+		return;
+	}
+
+	if (clk->opp_requested) {
+		prcmu_request_ape_opp_100_voltage(false);
+		clk->opp_requested = 0;
+	}
+
+	clk->is_prepared = 0;
 }
 
 static struct clk_ops clk_prcmu_scalable_ops = {
 	.prepare = clk_prcmu_prepare,
 	.unprepare = clk_prcmu_unprepare,
+	.is_prepared = clk_prcmu_is_prepared,
 	.enable = clk_prcmu_enable,
 	.disable = clk_prcmu_disable,
 	.is_enabled = clk_prcmu_is_enabled,
@@ -181,6 +202,7 @@ static struct clk_ops clk_prcmu_scalable_ops = {
 static struct clk_ops clk_prcmu_gate_ops = {
 	.prepare = clk_prcmu_prepare,
 	.unprepare = clk_prcmu_unprepare,
+	.is_prepared = clk_prcmu_is_prepared,
 	.enable = clk_prcmu_enable,
 	.disable = clk_prcmu_disable,
 	.is_enabled = clk_prcmu_is_enabled,
@@ -202,6 +224,7 @@ static struct clk_ops clk_prcmu_rate_ops = {
 static struct clk_ops clk_prcmu_opp_gate_ops = {
 	.prepare = clk_prcmu_opp_prepare,
 	.unprepare = clk_prcmu_opp_unprepare,
+	.is_prepared = clk_prcmu_is_prepared,
 	.enable = clk_prcmu_enable,
 	.disable = clk_prcmu_disable,
 	.is_enabled = clk_prcmu_is_enabled,
@@ -211,6 +234,7 @@ static struct clk_ops clk_prcmu_opp_gate_ops = {
 static struct clk_ops clk_prcmu_opp_volt_scalable_ops = {
 	.prepare = clk_prcmu_opp_volt_prepare,
 	.unprepare = clk_prcmu_opp_volt_unprepare,
+	.is_prepared = clk_prcmu_is_prepared,
 	.enable = clk_prcmu_enable,
 	.disable = clk_prcmu_disable,
 	.is_enabled = clk_prcmu_is_enabled,
@@ -242,7 +266,9 @@ static struct clk *clk_reg_prcmu(const char *name,
 	}
 
 	clk->cg_sel = cg_sel;
+	clk->is_prepared = 1;
 	clk->is_enabled = 1;
+	clk->opp_requested = 0;
 	/* "rate" can be used for changing the initial frequency */
 	if (rate)
 		prcmu_set_clock_rate(cg_sel, rate);
-- 
1.7.10

[PATCH 1/4] clk: Introduce optional is_prepared callback

[Mike Turquette]

Quoting Ulf Hansson (2013-01-24 08:45:53)
> From: Ulf Hansson <ulf.hansson@linaro.org>
> 
> To reflect whether a clk_hw is prepared the clk_hw may implement
> the optional is_prepared callback. If not implemented we fall back
> to use the software prepare counter.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> Acked-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/clk/clk.c            |   21 +++++++++++++++++++++
>  include/linux/clk-provider.h |    6 ++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 593a2e4..deb259a 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -458,6 +458,27 @@ unsigned long __clk_get_flags(struct clk *clk)
>         return !clk ? 0 : clk->flags;
>  }
>  
> +bool __clk_is_prepared(struct clk *clk)
> +{
> +       int ret;
> +
> +       if (!clk)
> +               return false;
> +
> +       /*
> +        * .is_prepared is optional for clocks that can prepare
> +        * fall back to software usage counter if it is missing
> +        */

Why not make it mandatory?  This could be as simple as saying "it is
mandatory", or we could even enforce a check in clk_init, though the
latter suggestion would be noisy until existing clock providers were
updated.

Note that .is_enabled is technically mandatory for any clock that
implements .enable/.disable but there is no check for compliance.  It is
only in Documentation/clk.txt and the kerneldoc.

Regards,
Mike

[PATCH 0/4] clk: Provide option to unprepare unused clocks at late init

[Mike Turquette]

Quoting Ulf Hansson (2013-01-24 08:45:52)
> From: Ulf Hansson <ulf.hansson@linaro.org>
> 
> The disable_unused sequence executed at late init, is already handling the
> fast unused ungated clocks to be gated. This patchset extends this sequence to
> include the slow unused prepared clocks to be unprepared.
> 
> The default behavior will not change in this patchset. To unprepare unused
> clocks during the disable_unused sequence, the clk_hw needs to implement
> the new optional callback, is_prepared.
> 
> The motivation for this patchset is to save power. Clocks that is from
> bootloaders prepared|enabled, but not used should be unprepared|disabled.
> 
> Patch 4 is specific for ux500, which implements the is_prepared callback
> for it's PRMCU clocks.
> 
> Note that patch 1-3 has been sent earlier, but since a proof of concept
> patch could be useful, as patch 4 is, the hole patchset is resent.
> 

Hi Ulf,

I had some minor discussion in patch #1.  Otherwise patches #2 & #3 look
good to me.

Patch #4 is a bit interesting.  There is nothing wrong with it per se,
but the general layering of the prcmu power stuff is the opposite of how
I had envisioned things.  Your .prepare callback is making calls to some
pm_qos api but a quick grep did not reveal any definitions for those
functions, just some stubs in include/linux/mfd/dbx500-prcmu.h.

Do these functions scale voltage?  I had figured that some day
per-device pm qos apis would call the clk api, not the other way around.

Anyways that is just food for thought and no reason to block patch #4.

Regards,
Mike

> Ulf Hansson (4):
>   clk: Introduce optional is_prepared callback
>   clk: Unprepare the unused prepared slow clocks at late init
>   clk: Introduce optional unprepare_unused callback
>   clk: ux500: Support is_prepared callback for clk-prcmu
> 
>  drivers/clk/clk.c             |   53 ++++++++++++++++
>  drivers/clk/ux500/clk-prcmu.c |  134 ++++++++++++++++++++++++-----------------
>  include/linux/clk-provider.h  |   11 ++++
>  3 files changed, 144 insertions(+), 54 deletions(-)
> 
> -- 
> 1.7.10

[PATCH 1/4] clk: Introduce optional is_prepared callback

[Ulf Hansson]

On 24 January 2013 19:12, Mike Turquette <mturquette@linaro.org> wrote:
> Quoting Ulf Hansson (2013-01-24 08:45:53)
>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>
>> To reflect whether a clk_hw is prepared the clk_hw may implement
>> the optional is_prepared callback. If not implemented we fall back
>> to use the software prepare counter.
>>
>> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
>> Acked-by: Linus Walleij <linus.walleij@linaro.org>
>> ---
>>  drivers/clk/clk.c            |   21 +++++++++++++++++++++
>>  include/linux/clk-provider.h |    6 ++++++
>>  2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index 593a2e4..deb259a 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -458,6 +458,27 @@ unsigned long __clk_get_flags(struct clk *clk)
>>         return !clk ? 0 : clk->flags;
>>  }
>>
>> +bool __clk_is_prepared(struct clk *clk)
>> +{
>> +       int ret;
>> +
>> +       if (!clk)
>> +               return false;
>> +
>> +       /*
>> +        * .is_prepared is optional for clocks that can prepare
>> +        * fall back to software usage counter if it is missing
>> +        */
>
> Why not make it mandatory?  This could be as simple as saying "it is
> mandatory", or we could even enforce a check in clk_init, though the
> latter suggestion would be noisy until existing clock providers were
> updated.

I was trying to go "slow" forward and wanted to keep the same
behaviour for how .is_enabled is handled.

I am positive in making this mandatory, but then this should be
applied for is_enabled as well. If we make something mandatory I
definitely think it shall be checked in clk_int, it makes sense to me.

>
> Note that .is_enabled is technically mandatory for any clock that
> implements .enable/.disable but there is no check for compliance.  It is
> only in Documentation/clk.txt and the kerneldoc.

According to the clk-provider.h file:
------
 * @is_enabled: Queries the hardware to determine if the clock is enabled.
 *              This function must not sleep. Optional, if this op is not
 *              set then the enable count will be used.
-----

The  Documentation/clk.txt says it is mandatory. :-) So we have a kind
of mixed message here.

>
> Regards,
> Mike

Kind regards
Ulf Hansson

[PATCH 0/4] clk: Provide option to unprepare unused clocks at late init

[Ulf Hansson]

Hi Mike,

On 24 January 2013 19:49, Mike Turquette <mturquette@linaro.org> wrote:
> Quoting Ulf Hansson (2013-01-24 08:45:52)
>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>
>> The disable_unused sequence executed at late init, is already handling the
>> fast unused ungated clocks to be gated. This patchset extends this sequence to
>> include the slow unused prepared clocks to be unprepared.
>>
>> The default behavior will not change in this patchset. To unprepare unused
>> clocks during the disable_unused sequence, the clk_hw needs to implement
>> the new optional callback, is_prepared.
>>
>> The motivation for this patchset is to save power. Clocks that is from
>> bootloaders prepared|enabled, but not used should be unprepared|disabled.
>>
>> Patch 4 is specific for ux500, which implements the is_prepared callback
>> for it's PRMCU clocks.
>>
>> Note that patch 1-3 has been sent earlier, but since a proof of concept
>> patch could be useful, as patch 4 is, the hole patchset is resent.
>>
>
> Hi Ulf,
>
> I had some minor discussion in patch #1.  Otherwise patches #2 & #3 look
> good to me.
>
> Patch #4 is a bit interesting.  There is nothing wrong with it per se,
> but the general layering of the prcmu power stuff is the opposite of how
> I had envisioned things.  Your .prepare callback is making calls to some
> pm_qos api but a quick grep did not reveal any definitions for those
> functions, just some stubs in include/linux/mfd/dbx500-prcmu.h.
>
> Do these functions scale voltage?  I had figured that some day
> per-device pm qos apis would call the clk api, not the other way around.

You are right, these scale voltages. I would like to keep the code as
is, just as a reminder that some devices using some clocks will
requires these kind of operations.
On our internal STE development track this is how it is used but we a
are moving towards newer APIs.

So I am definitely sharing the same thought as you do and my plan is
to remove this code along the road, once drivers is adapted properly.

>
> Anyways that is just food for thought and no reason to block patch #4.
>
> Regards,
> Mike
>
>> Ulf Hansson (4):
>>   clk: Introduce optional is_prepared callback
>>   clk: Unprepare the unused prepared slow clocks at late init
>>   clk: Introduce optional unprepare_unused callback
>>   clk: ux500: Support is_prepared callback for clk-prcmu
>>
>>  drivers/clk/clk.c             |   53 ++++++++++++++++
>>  drivers/clk/ux500/clk-prcmu.c |  134 ++++++++++++++++++++++++-----------------
>>  include/linux/clk-provider.h  |   11 ++++
>>  3 files changed, 144 insertions(+), 54 deletions(-)
>>
>> --
>> 1.7.10

Thanks for the review comments!

Kind regards
Ulf Hansson

[PATCH 0/4] clk: Provide option to unprepare unused clocks at late init

[Ulf Hansson]

On 24 January 2013 21:41, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> Hi Mike,
>
> On 24 January 2013 19:49, Mike Turquette <mturquette@linaro.org> wrote:
>> Quoting Ulf Hansson (2013-01-24 08:45:52)
>>> From: Ulf Hansson <ulf.hansson@linaro.org>
>>>
>>> The disable_unused sequence executed at late init, is already handling the
>>> fast unused ungated clocks to be gated. This patchset extends this sequence to
>>> include the slow unused prepared clocks to be unprepared.
>>>
>>> The default behavior will not change in this patchset. To unprepare unused
>>> clocks during the disable_unused sequence, the clk_hw needs to implement
>>> the new optional callback, is_prepared.
>>>
>>> The motivation for this patchset is to save power. Clocks that is from
>>> bootloaders prepared|enabled, but not used should be unprepared|disabled.
>>>
>>> Patch 4 is specific for ux500, which implements the is_prepared callback
>>> for it's PRMCU clocks.
>>>
>>> Note that patch 1-3 has been sent earlier, but since a proof of concept
>>> patch could be useful, as patch 4 is, the hole patchset is resent.
>>>
>>
>> Hi Ulf,
>>
>> I had some minor discussion in patch #1.  Otherwise patches #2 & #3 look
>> good to me.
>>
>> Patch #4 is a bit interesting.  There is nothing wrong with it per se,
>> but the general layering of the prcmu power stuff is the opposite of how
>> I had envisioned things.  Your .prepare callback is making calls to some
>> pm_qos api but a quick grep did not reveal any definitions for those
>> functions, just some stubs in include/linux/mfd/dbx500-prcmu.h.
>>
>> Do these functions scale voltage?  I had figured that some day
>> per-device pm qos apis would call the clk api, not the other way around.
>
> You are right, these scale voltages. I would like to keep the code as
> is, just as a reminder that some devices using some clocks will
> requires these kind of operations.
> On our internal STE development track this is how it is used but we a
> are moving towards newer APIs.
>
> So I am definitely sharing the same thought as you do and my plan is
> to remove this code along the road, once drivers is adapted properly.
>
>>
>> Anyways that is just food for thought and no reason to block patch #4.
>>
>> Regards,
>> Mike
>>
>>> Ulf Hansson (4):
>>>   clk: Introduce optional is_prepared callback
>>>   clk: Unprepare the unused prepared slow clocks at late init
>>>   clk: Introduce optional unprepare_unused callback
>>>   clk: ux500: Support is_prepared callback for clk-prcmu
>>>
>>>  drivers/clk/clk.c             |   53 ++++++++++++++++
>>>  drivers/clk/ux500/clk-prcmu.c |  134 ++++++++++++++++++++++++-----------------
>>>  include/linux/clk-provider.h  |   11 ++++
>>>  3 files changed, 144 insertions(+), 54 deletions(-)
>>>
>>> --
>>> 1.7.10
>
> Thanks for the review comments!
>
> Kind regards
> Ulf Hansson

Ping, on this. Any issues merging this for 3.9?

Kind regards
Ulf Hansson