[RFC v1 0/1] introduce regulator chain locking scheme

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* [RFC v1 0/1] introduce regulator chain locking scheme
@ 2013-04-15 13:03 Grygorii Strashko
  2013-04-15 13:03 ` [RFC v1] regulator: core: " Grygorii Strashko
  0 siblings, 1 reply; 6+ messages in thread
From: Grygorii Strashko @ 2013-04-15 13:03 UTC (permalink / raw)
  To: Liam Girdwood, Mark Brown
  Cc: Grygorii Strashko, open list, Mike Turquette, Tero Kristo,
	Nishanth Menon, linux-omap, linux-arm

Hi Mark, Liam, All

Our target is to reuse common DVFS framework proposed by Mike Turquette
in http://lwn.net/Articles/540422/ and cpufreq-cpu0.c for all TI SoC and
minimize creation of any TI specific APIs or modules.
The common DVFS framework solution is based on assumption that Regulator,
connected to DVFS FW or CPU0 CPUFreq, is able to change requested voltage for
the corresponding Voltage domain (like CPU/MPU) by itself.
But most of TI SoCs, which support DVFS, have more complex voltage supply
schema as shown below:

  |------------|  |------------|
--| RegulatorY |--| CPU DVFS   |
  |------------|  |------------|
   \           \
    \           \_____________________________
     \                                        \
     |-------------------|  |---------------|  |---------|
   --| RegulatorX (PMIC) |--| Regulator AVS |--| ABB LDO |--
     |-------------------|  |---------------|  |---------|
		/|\				        |					
         |______________________|
         Voltage adjustment

and they need to configure, at least, internal ABB LDO befor/after
reconfiguring external voltage supplier in PMIC.
(as maximum - Regulator AVS (Adaptive voltage scaling) is needed to be
reconfigured after ABB LDO, and Regulator AVS may, finally, reconfigure external
voltage supplier with voltage value which is different from initially requested by DVFS).

for example (Vcur<Vreq):
- DVFS requests voltage change
- AVS converts Vreq to Vreq1 (say calibrated)
- AVS reconfigure RegulatorX (PMIC) to voltage Vreq1
- ABB LDO change type to FBB

This Regulator chaining scema can fit to Regulator framework very well
(from our point of view):
- DVFS: abb->set_voltage(Vreq)
- ABB: if (Vcur<Vreq)
			AVS->set_voltage(Vreq)
- AVS: PMIC->set_voltage(Vreq1)
- ABB: if (Vcur<Vreq)
			change type to FBB

But there are some limitations:
 - the whole Regulator chain need to be locked in case if any part of
   it has been accessed from outside;
 - child regulator should have access to set/get voltage methods of its 
   parent (supplier).

The proposed patches allow to remove these restrictions and they are inspired by
http://lwn.net/Articles/540422/.

Related dicussions:
 - regulator: query on regulator re-entrance 
   http://marc.info/?l=linux-omap&m=136513861315970&w=2
 - clk: notifier handler for dynamic voltage scaling
   https://lkml.org/lkml/2013/2/27/414

Tested on K3.8 OMAP4 SDP/T2 (ABB+vcvp regulator) and
OMAP5 sevm (ABB+smps123(i2c) regulator):
- cpu freq & voltages was scaled.

Could you please review and advise? Does anyone else interested in or have similar problems?

Grygorii Strashko (1):
  regulator: core: introduce regulator chain locking scheme

 drivers/regulator/core.c         |  134 ++++++++++++++++++++++++--------------
 include/linux/regulator/driver.h |    2 +
 2 files changed, 88 insertions(+), 48 deletions(-)

Regards
Grygorii Strashko

Cc: linux-kernel@vger.kernel.org (open list)
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: linux-omap <linux-omap@vger.kernel.org>
Cc: linux-arm <linux-arm-kernel@lists.infradead.org>
-- 
1.7.9.5

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [RFC v1] regulator: core: introduce regulator chain locking scheme
  2013-04-15 13:03 [RFC v1 0/1] introduce regulator chain locking scheme Grygorii Strashko
@ 2013-04-15 13:03 ` Grygorii Strashko
  2013-04-15 15:50   ` Mark Brown
  0 siblings, 1 reply; 6+ messages in thread
From: Grygorii Strashko @ 2013-04-15 13:03 UTC (permalink / raw)
  To: Liam Girdwood, Mark Brown
  Cc: Grygorii Strashko, linux-kernel, Mike Turquette, Nishanth Menon,
	Tero Kristo, linux-omap, linux-arm

In some cases the regulators may be organized in a chain like:
  ->regA->regB->regC
where regA is supplier for regB and regB is supplier for regC.

Currently it would be possible to reconfigure regA and regC at same time
form different contexts, because each regulator has it own mutex.
But in some cases, the only the whole chain is allowed be reconfigured
because of dependencies between regulators - to change regB
configuration the regA need to be updated first.

Hence, introduce regulator chain locking scheme to lock whole Regulator
chain in case if any part of it has been accessed from outside.

To achieve this goal:
- abstract regulator locking out into helper functions;
- use the root Regulator (which has no supply defined, like regA) in chain to
  protect the whole chain;
- implement regulator chain locking scheme as proposed by Thomas Gleixner for CCF
  re-entrance in https://lkml.org/lkml/2013/3/27/171 and in the similar way as
  it is done for CCF by Mike Turquette in https://lkml.org/lkml/2013/3/28/512

In addition, such locking scheme allows to have access to the supplier
regulator API from inside child's (consumer) regulator API.

Cc: linux-kernel@vger.kernel.org
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: linux-omap <linux-omap@vger.kernel.org>
Cc: linux-arm <linux-arm-kernel@lists.infradead.org>

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/regulator/core.c         |  134 ++++++++++++++++++++++++--------------
 include/linux/regulator/driver.h |    2 +
 2 files changed, 88 insertions(+), 48 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index e3661c2..089cc63 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -110,6 +110,44 @@ static const char *rdev_get_name(struct regulator_dev *rdev)
 		return "";
 }
 
+static void regulator_lock(struct regulator_dev *rdev)
+{
+	struct regulator_dev *locking_rdev = rdev;
+
+	while (locking_rdev->supply)
+		locking_rdev = locking_rdev->supply->rdev;
+
+	if (!mutex_trylock(&locking_rdev->mutex)) {
+		if (locking_rdev->lock_owner == current) {
+			locking_rdev->lock_count++;
+			return;
+		}
+		mutex_lock(&locking_rdev->mutex);
+	}
+
+	WARN_ON_ONCE(locking_rdev->lock_owner != NULL);
+	WARN_ON_ONCE(locking_rdev->lock_count != 0);
+
+	locking_rdev->lock_count = 1;
+	locking_rdev->lock_owner = current;
+	dev_dbg(&locking_rdev->dev, "Is locked. locking %s\n",
+		rdev_get_name(rdev));
+}
+
+static void regulator_unlock(struct regulator_dev *rdev)
+{
+	struct regulator_dev *locking_rdev = rdev;
+
+	while (locking_rdev->supply)
+		locking_rdev = locking_rdev->supply->rdev;
+
+	if (--locking_rdev->lock_count)
+		return;
+
+	locking_rdev->lock_owner = NULL;
+	mutex_unlock(&locking_rdev->mutex);
+}
+
 /**
  * of_get_regulator - get a regulator device node based on supply name
  * @dev: Device pointer for the consumer (of regulator) device
@@ -292,9 +330,9 @@ static ssize_t regulator_uV_show(struct device *dev,
 	struct regulator_dev *rdev = dev_get_drvdata(dev);
 	ssize_t ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	ret = sprintf(buf, "%d\n", _regulator_get_voltage(rdev));
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	return ret;
 }
@@ -357,9 +395,9 @@ static ssize_t regulator_state_show(struct device *dev,
 	struct regulator_dev *rdev = dev_get_drvdata(dev);
 	ssize_t ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	ret = regulator_print_state(buf, _regulator_is_enabled(rdev));
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	return ret;
 }
@@ -467,10 +505,10 @@ static ssize_t regulator_total_uA_show(struct device *dev,
 	struct regulator *regulator;
 	int uA = 0;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	list_for_each_entry(regulator, &rdev->consumer_list, list)
 		uA += regulator->uA_load;
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return sprintf(buf, "%d\n", uA);
 }
 static DEVICE_ATTR(requested_microamps, 0444, regulator_total_uA_show, NULL);
@@ -1104,7 +1142,7 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
 	if (regulator == NULL)
 		return NULL;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	regulator->rdev = rdev;
 	list_add(&regulator->list, &rdev->consumer_list);
 
@@ -1156,12 +1194,12 @@ static struct regulator *create_regulator(struct regulator_dev *rdev,
 	    _regulator_is_enabled(rdev))
 		regulator->always_on = true;
 
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return regulator;
 overflow_err:
 	list_del(&regulator->list);
 	kfree(regulator);
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return NULL;
 }
 
@@ -1558,9 +1596,9 @@ int regulator_enable(struct regulator *regulator)
 			return ret;
 	}
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	ret = _regulator_enable(rdev);
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	if (ret != 0 && rdev->supply)
 		regulator_disable(rdev->supply);
@@ -1649,9 +1687,9 @@ int regulator_disable(struct regulator *regulator)
 	if (regulator->always_on)
 		return 0;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	ret = _regulator_disable(rdev);
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	if (ret == 0 && rdev->supply)
 		regulator_disable(rdev->supply);
@@ -1695,10 +1733,10 @@ int regulator_force_disable(struct regulator *regulator)
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	regulator->uA_load = 0;
 	ret = _regulator_force_disable(regulator->rdev);
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	if (rdev->supply)
 		while (rdev->open_count--)
@@ -1714,7 +1752,7 @@ static void regulator_disable_work(struct work_struct *work)
 						  disable_work.work);
 	int count, i, ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	BUG_ON(!rdev->deferred_disables);
 
@@ -1727,7 +1765,7 @@ static void regulator_disable_work(struct work_struct *work)
 			rdev_err(rdev, "Deferred disable failed: %d\n", ret);
 	}
 
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	if (rdev->supply) {
 		for (i = 0; i < count; i++) {
@@ -1763,9 +1801,9 @@ int regulator_disable_deferred(struct regulator *regulator, int ms)
 	if (!ms)
 		return regulator_disable(regulator);
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	rdev->deferred_disables++;
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	ret = schedule_delayed_work(&rdev->disable_work,
 				    msecs_to_jiffies(ms));
@@ -1863,9 +1901,9 @@ int regulator_is_enabled(struct regulator *regulator)
 	if (regulator->always_on)
 		return 1;
 
-	mutex_lock(&regulator->rdev->mutex);
+	regulator_lock(regulator->rdev);
 	ret = _regulator_is_enabled(regulator->rdev);
-	mutex_unlock(&regulator->rdev->mutex);
+	regulator_unlock(regulator->rdev);
 
 	return ret;
 }
@@ -1983,9 +2021,9 @@ int regulator_list_voltage(struct regulator *regulator, unsigned selector)
 	if (!ops->list_voltage || selector >= rdev->desc->n_voltages)
 		return -EINVAL;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 	ret = ops->list_voltage(rdev, selector);
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	if (ret > 0) {
 		if (ret < rdev->constraints->min_uV)
@@ -2309,7 +2347,7 @@ int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV)
 	int ret = 0;
 	int old_min_uV, old_max_uV;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/* If we're setting the same range as last time the change
 	 * should be a noop (some cpufreq implementations use the same
@@ -2345,12 +2383,12 @@ int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV)
 		goto out2;
 	
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 out2:
 	regulator->min_uV = old_min_uV;
 	regulator->max_uV = old_max_uV;
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_set_voltage);
@@ -2453,7 +2491,7 @@ int regulator_sync_voltage(struct regulator *regulator)
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret, min_uV, max_uV;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	if (!rdev->desc->ops->set_voltage &&
 	    !rdev->desc->ops->set_voltage_sel) {
@@ -2482,7 +2520,7 @@ int regulator_sync_voltage(struct regulator *regulator)
 	ret = _regulator_do_set_voltage(rdev, min_uV, max_uV);
 
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_sync_voltage);
@@ -2522,11 +2560,11 @@ int regulator_get_voltage(struct regulator *regulator)
 {
 	int ret;
 
-	mutex_lock(&regulator->rdev->mutex);
+	regulator_lock(regulator->rdev);
 
 	ret = _regulator_get_voltage(regulator->rdev);
 
-	mutex_unlock(&regulator->rdev->mutex);
+	regulator_unlock(regulator->rdev);
 
 	return ret;
 }
@@ -2554,7 +2592,7 @@ int regulator_set_current_limit(struct regulator *regulator,
 	struct regulator_dev *rdev = regulator->rdev;
 	int ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/* sanity check */
 	if (!rdev->desc->ops->set_current_limit) {
@@ -2569,7 +2607,7 @@ int regulator_set_current_limit(struct regulator *regulator,
 
 	ret = rdev->desc->ops->set_current_limit(rdev, min_uA, max_uA);
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_set_current_limit);
@@ -2578,7 +2616,7 @@ static int _regulator_get_current_limit(struct regulator_dev *rdev)
 {
 	int ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/* sanity check */
 	if (!rdev->desc->ops->get_current_limit) {
@@ -2588,7 +2626,7 @@ static int _regulator_get_current_limit(struct regulator_dev *rdev)
 
 	ret = rdev->desc->ops->get_current_limit(rdev);
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 
@@ -2624,7 +2662,7 @@ int regulator_set_mode(struct regulator *regulator, unsigned int mode)
 	int ret;
 	int regulator_curr_mode;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/* sanity check */
 	if (!rdev->desc->ops->set_mode) {
@@ -2648,7 +2686,7 @@ int regulator_set_mode(struct regulator *regulator, unsigned int mode)
 
 	ret = rdev->desc->ops->set_mode(rdev, mode);
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_set_mode);
@@ -2657,7 +2695,7 @@ static unsigned int _regulator_get_mode(struct regulator_dev *rdev)
 {
 	int ret;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/* sanity check */
 	if (!rdev->desc->ops->get_mode) {
@@ -2667,7 +2705,7 @@ static unsigned int _regulator_get_mode(struct regulator_dev *rdev)
 
 	ret = rdev->desc->ops->get_mode(rdev);
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 
@@ -2719,7 +2757,7 @@ int regulator_set_optimum_mode(struct regulator *regulator, int uA_load)
 	if (rdev->supply)
 		input_uV = regulator_get_voltage(rdev->supply);
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	/*
 	 * first check to see if we can set modes at all, otherwise just
@@ -2780,7 +2818,7 @@ int regulator_set_optimum_mode(struct regulator *regulator, int uA_load)
 	}
 	ret = mode;
 out:
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(regulator_set_optimum_mode);
@@ -2849,7 +2887,7 @@ int regulator_allow_bypass(struct regulator *regulator, bool enable)
 	    !(rdev->constraints->valid_ops_mask & REGULATOR_CHANGE_BYPASS))
 		return 0;
 
-	mutex_lock(&rdev->mutex);
+	regulator_lock(rdev);
 
 	if (enable && !regulator->bypass) {
 		rdev->bypass_count++;
@@ -2873,7 +2911,7 @@ int regulator_allow_bypass(struct regulator *regulator, bool enable)
 	if (ret == 0)
 		regulator->bypass = enable;
 
-	mutex_unlock(&rdev->mutex);
+	regulator_unlock(rdev);
 
 	return ret;
 }
@@ -3588,9 +3626,9 @@ int regulator_suspend_prepare(suspend_state_t state)
 	mutex_lock(&regulator_list_mutex);
 	list_for_each_entry(rdev, &regulator_list, list) {
 
-		mutex_lock(&rdev->mutex);
+		regulator_lock(rdev);
 		ret = suspend_prepare(rdev, state);
-		mutex_unlock(&rdev->mutex);
+		regulator_unlock(rdev);
 
 		if (ret < 0) {
 			rdev_err(rdev, "failed to prepare\n");
@@ -3618,7 +3656,7 @@ int regulator_suspend_finish(void)
 	list_for_each_entry(rdev, &regulator_list, list) {
 		struct regulator_ops *ops = rdev->desc->ops;
 
-		mutex_lock(&rdev->mutex);
+		regulator_lock(rdev);
 		if ((rdev->use_count > 0  || rdev->constraints->always_on) &&
 				ops->enable) {
 			error = ops->enable(rdev);
@@ -3637,7 +3675,7 @@ int regulator_suspend_finish(void)
 				ret = error;
 		}
 unlock:
-		mutex_unlock(&rdev->mutex);
+		regulator_unlock(rdev);
 	}
 	mutex_unlock(&regulator_list_mutex);
 	return ret;
@@ -3825,7 +3863,7 @@ static int __init regulator_init_complete(void)
 		if (!ops->disable || (c && c->always_on))
 			continue;
 
-		mutex_lock(&rdev->mutex);
+		regulator_lock(rdev);
 
 		if (rdev->use_count)
 			goto unlock;
@@ -3857,7 +3895,7 @@ static int __init regulator_init_complete(void)
 		}
 
 unlock:
-		mutex_unlock(&rdev->mutex);
+		regulator_unlock(rdev);
 	}
 
 	mutex_unlock(&regulator_list_mutex);
diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 7df93f5..6bfa2af 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -289,6 +289,8 @@ struct regulator_dev {
 
 	struct blocking_notifier_head notifier;
 	struct mutex mutex; /* consumer lock */
+	struct task_struct *lock_owner; /* consumer thread context */
+	int lock_count; /* number of recursive locks taken */
 	struct module *owner;
 	struct device dev;
 	struct regulation_constraints *constraints;
-- 
1.7.9.5


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [RFC v1] regulator: core: introduce regulator chain locking scheme
  2013-04-15 13:03 ` [RFC v1] regulator: core: " Grygorii Strashko
@ 2013-04-15 15:50   ` Mark Brown
  2013-04-15 16:21     ` Andrii Tseglytskyi
  0 siblings, 1 reply; 6+ messages in thread
From: Mark Brown @ 2013-04-15 15:50 UTC (permalink / raw)
  To: Grygorii Strashko
  Cc: Liam Girdwood, linux-kernel, Mike Turquette, Nishanth Menon,
	Tero Kristo, linux-omap, linux-arm

[-- Attachment #1: Type: text/plain, Size: 792 bytes --]

On Mon, Apr 15, 2013 at 04:03:35PM +0300, Grygorii Strashko wrote:

> To achieve this goal:
> - abstract regulator locking out into helper functions;
> - use the root Regulator (which has no supply defined, like regA) in chain to
>   protect the whole chain;
> - implement regulator chain locking scheme as proposed by Thomas Gleixner for CCF
>   re-entrance in https://lkml.org/lkml/2013/3/27/171 and in the similar way as
>   it is done for CCF by Mike Turquette in https://lkml.org/lkml/2013/3/28/512

Split this into separate refactoring and other change commits - one
change per commit.

> In addition, such locking scheme allows to have access to the supplier
> regulator API from inside child's (consumer) regulator API.

I've still not seen any use case articulated for doing this...

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RFC v1] regulator: core: introduce regulator chain locking scheme
  2013-04-15 15:50   ` Mark Brown
@ 2013-04-15 16:21     ` Andrii Tseglytskyi
  2013-04-15 16:40       ` Mark Brown
  0 siblings, 1 reply; 6+ messages in thread
From: Andrii Tseglytskyi @ 2013-04-15 16:21 UTC (permalink / raw)
  To: Mark Brown
  Cc: Nishanth Menon, Tero Kristo, Grygorii Strashko, Mike Turquette,
	linux-kernel, Liam Girdwood, linux-omap, linux-arm

Hi Mark,

On 04/15/2013 06:50 PM, Mark Brown wrote:
>> In addition, such locking scheme allows to have access to the supplier
>> regulator API from inside child's (consumer) regulator API.
> I've still not seen any use case articulated for doing this...
Use case is introduced in ABB series:

http://www.mail-archive.com/linux-omap@vger.kernel.org/msg88293.html

During voltage scaling we would like to have the following sequence:

cpufreq_cpu0
     |
     |---> set_voltage(ABB)
                 |
                 |->set_voltage(AVS)
                         |
                         |-->set_voltage(smps123)


Where smps123 is a regulator, connected ot i2c bus. In this particular 
case "regulator chain" guarantees proper order of calls of voltage 
scaling sequence.

Regards,
Andrii

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RFC v1] regulator: core: introduce regulator chain locking scheme
  2013-04-15 16:21     ` Andrii Tseglytskyi
@ 2013-04-15 16:40       ` Mark Brown
  2013-04-18 16:29         ` Grygorii Strashko
  0 siblings, 1 reply; 6+ messages in thread
From: Mark Brown @ 2013-04-15 16:40 UTC (permalink / raw)
  To: Andrii Tseglytskyi
  Cc: Mark Brown, Grygorii Strashko, Liam Girdwood, linux-kernel,
	Mike Turquette, Nishanth Menon, Tero Kristo, linux-omap,
	linux-arm

On Mon, Apr 15, 2013 at 07:21:25PM +0300, Andrii Tseglytskyi wrote:
> On 04/15/2013 06:50 PM, Mark Brown wrote:

> >>In addition, such locking scheme allows to have access to the supplier
> >>regulator API from inside child's (consumer) regulator API.

> >I've still not seen any use case articulated for doing this...

> Use case is introduced in ABB series:

Sorry, I meant any sensible use case.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [RFC v1] regulator: core: introduce regulator chain locking scheme
  2013-04-15 16:40       ` Mark Brown
@ 2013-04-18 16:29         ` Grygorii Strashko
  0 siblings, 0 replies; 6+ messages in thread
From: Grygorii Strashko @ 2013-04-18 16:29 UTC (permalink / raw)
  To: Mark Brown
  Cc: Nishanth Menon, Tero Kristo, Mike Turquette, Andrii Tseglytskyi,
	linux-kernel, Liam Girdwood, Mark Brown, linux-omap, linux-arm

On 04/15/2013 07:40 PM, Mark Brown wrote:
> On Mon, Apr 15, 2013 at 07:21:25PM +0300, Andrii Tseglytskyi wrote:
>> On 04/15/2013 06:50 PM, Mark Brown wrote:
>>>> In addition, such locking scheme allows to have access to the supplier
>>>> regulator API from inside child's (consumer) regulator API.
>>> I've still not seen any use case articulated for doing this...
>> Use case is introduced in ABB series:
> Sorry, I meant any sensible use case.
Hi Mark,

Thanks for you comments. I'll split it to 3 patches:
- abstract locking out into helper functions;
- introduce regulator chain locking scheme
- allow reentrant calls into the regulator framework (with hope that is 
has future,
may be can enable/disable it through constraints)

I understand that Regulator FW is common and wide used and we should 
very careful here.

Regards,
- grygorii

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2013-04-18 16:29 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-04-15 13:03 [RFC v1 0/1] introduce regulator chain locking scheme Grygorii Strashko
2013-04-15 13:03 ` [RFC v1] regulator: core: " Grygorii Strashko
2013-04-15 15:50   ` Mark Brown
2013-04-15 16:21     ` Andrii Tseglytskyi
2013-04-15 16:40       ` Mark Brown
2013-04-18 16:29         ` Grygorii Strashko

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