diff mbox series

[6/8] PM / OPP: Support adjusting OPP voltages at runtime

Message ID 1557997725-12178-7-git-send-email-andrew-sh.cheng@mediatek.com (mailing list archive)
State New, archived
Headers show
Series Add cpufreq and cci devfreq for mt8183, and SVS support | expand

Commit Message

andrew-sh.cheng May 16, 2019, 9:08 a.m. UTC 
From: Stephen Boyd <sboyd@codeaurora.org>

On some SoCs the Adaptive Voltage Scaling (AVS) technique is
employed to optimize the operating voltage of a device. At a
given frequency, the hardware monitors dynamic factors and either
makes a suggestion for how much to adjust a voltage for the
current frequency, or it automatically adjusts the voltage
without software intervention. Add an API to the OPP library for
the former case, so that AVS type devices can update the voltages
for an OPP when the hardware determines the voltage should
change. The assumption is that drivers like CPUfreq or devfreq
will register for the OPP notifiers and adjust the voltage
according to suggestions that AVS makes.

This patch is devired from [1] submitted by Stephen.
[1] https://lore.kernel.org/patchwork/patch/599279/

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Roger Lu <roger.lu@mediatek.com>
---
 drivers/opp/core.c     | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pm_opp.h | 11 +++++++
 2 files changed, 89 insertions(+)

Comments

Viresh Kumar May 20, 2019, 4:47 a.m. UTC | #1 
On 16-05-19, 17:08, Andrew-sh.Cheng wrote:
> From: Stephen Boyd <sboyd@codeaurora.org>
> 
> On some SoCs the Adaptive Voltage Scaling (AVS) technique is
> employed to optimize the operating voltage of a device. At a
> given frequency, the hardware monitors dynamic factors and either
> makes a suggestion for how much to adjust a voltage for the
> current frequency, or it automatically adjusts the voltage
> without software intervention. Add an API to the OPP library for
> the former case, so that AVS type devices can update the voltages
> for an OPP when the hardware determines the voltage should
> change. The assumption is that drivers like CPUfreq or devfreq
> will register for the OPP notifiers and adjust the voltage
> according to suggestions that AVS makes.
> 
> This patch is devired from [1] submitted by Stephen.
> [1] https://lore.kernel.org/patchwork/patch/599279/
> 
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> Signed-off-by: Roger Lu <roger.lu@mediatek.com>
> ---
>  drivers/opp/core.c     | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm_opp.h | 11 +++++++
>  2 files changed, 89 insertions(+)

This is an rcu implementation which got removed long back from OPP core. Please
align this with the latest changes.
Roger Lu July 29, 2019, 3:39 a.m. UTC | #2 
Dear Stephen Boyd,

This patch is derived from [1]. Please kindly shares the suggestion to
us. Thanks very much.

[1]: https://lore.kernel.org/patchwork/patch/599279/

Dear Viresh,

I followed _opp_set_availability() coding style to refine
dev_pm_opp_adjust_voltage() from this patch. Is this refinement suitable
for OPP core? Thanks a lot.

On Mon, 2019-05-20 at 12:47 +0800, Viresh Kumar wrote:
> On 16-05-19, 17:08, Andrew-sh.Cheng wrote:
> > From: Stephen Boyd <sboyd@codeaurora.org>
> > 
> > On some SoCs the Adaptive Voltage Scaling (AVS) technique is
> > employed to optimize the operating voltage of a device. At a
> > given frequency, the hardware monitors dynamic factors and either
> > makes a suggestion for how much to adjust a voltage for the
> > current frequency, or it automatically adjusts the voltage
> > without software intervention. Add an API to the OPP library for
> > the former case, so that AVS type devices can update the voltages
> > for an OPP when the hardware determines the voltage should
> > change. The assumption is that drivers like CPUfreq or devfreq
> > will register for the OPP notifiers and adjust the voltage
> > according to suggestions that AVS makes.
> > 
> > This patch is devired from [1] submitted by Stephen.
> > [1] https://lore.kernel.org/patchwork/patch/599279/
> > 
> > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> > Signed-off-by: Roger Lu <roger.lu@mediatek.com>
> > ---
> >  drivers/opp/core.c     | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/pm_opp.h | 11 +++++++
> >  2 files changed, 89 insertions(+)
> 
> This is an rcu implementation which got removed long back from OPP core. Please
> align this with the latest changes.
> 


/**
 * dev_pm_opp_adjust_voltage() - helper to change the voltage of an OPP
 * @dev:		device for which we do this operation
 * @freq:		OPP frequency to adjust voltage of
 * @u_volt:		new OPP voltage
 *
 * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for
the
 * copy operation, returns 0 if no modifcation was done OR modification
was
 * successful.
 */
int dev_pm_opp_adjust_voltage(struct device *dev, unsigned long freq,
			      unsigned long u_volt)
{
	struct opp_table *opp_table;
	struct dev_pm_opp *tmp_opp, *opp = ERR_PTR(-ENODEV);
	int r = 0;

	/* Find the opp_table */
	opp_table = _find_opp_table(dev);
	if (IS_ERR(opp_table)) {
		r = PTR_ERR(opp_table);
		dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
		return r;
	}

	mutex_lock(&opp_table->lock);

	/* Do we have the frequency? */
	list_for_each_entry(tmp_opp, &opp_table->opp_list, node) {
		if (tmp_opp->rate == freq) {
			opp = tmp_opp;
			break;
		}
	}

	if (IS_ERR(opp)) {
		r = PTR_ERR(opp);
		goto adjust_unlock;
	}

	/* Is update really needed? */
	if (opp->supplies->u_volt == u_volt)
		goto adjust_unlock;

	opp->supplies->u_volt = u_volt;

	dev_pm_opp_get(opp);
	mutex_unlock(&opp_table->lock);

	/* Notify the voltage change of the OPP */
	blocking_notifier_call_chain(&opp_table->head,
OPP_EVENT_ADJUST_VOLTAGE,
				     opp);

	dev_pm_opp_put(opp);
	goto adjust_put_table;

adjust_unlock:
	mutex_unlock(&opp_table->lock);
adjust_put_table:
	dev_pm_opp_put_opp_table(opp_table);
	return r;
}

Sincerely,
Roger Lu.
Viresh Kumar July 29, 2019, 9:20 a.m. UTC | #3 
On 29-07-19, 11:39, Roger Lu wrote:
> Dear Stephen Boyd,
> 
> This patch is derived from [1]. Please kindly shares the suggestion to
> us. Thanks very much.
> 
> [1]: https://lore.kernel.org/patchwork/patch/599279/
> 
> Dear Viresh,
> 
> I followed _opp_set_availability() coding style to refine
> dev_pm_opp_adjust_voltage() from this patch. Is this refinement suitable
> for OPP core? Thanks a lot.

Looks okay from a quick look.
diff mbox series

Patch

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 0420f7e8ad5b..879ca5f50d1a 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1946,6 +1946,84 @@  static int _opp_set_availability(struct device *dev, unsigned long freq,
 	return r;
 }
 
+/*
+ * dev_pm_opp_adjust_voltage() - helper to change the voltage of an OPP
+ * @dev:		device for which we do this operation
+ * @freq:		OPP frequency to adjust voltage of
+ * @u_volt:		new OPP voltage
+ *
+ * Change the voltage of an OPP with an RCU operation.
+ *
+ * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for the
+ * copy operation, returns 0 if no modifcation was done OR modification was
+ * successful.
+ *
+ * Locking: The internal device_opp and opp structures are RCU protected.
+ * Hence this function internally uses RCU updater strategy with mutex locks to
+ * keep the integrity of the internal data structures. Callers should ensure
+ * that this function is *NOT* called under RCU protection or in contexts where
+ * mutex locking or synchronize_rcu() blocking calls cannot be used.
+ */
+int dev_pm_opp_adjust_voltage(struct device *dev, unsigned long freq,
+			      unsigned long u_volt)
+{
+	struct opp_table *opp_table;
+	struct dev_pm_opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
+	int r = 0;
+
+	/* Find the opp_table */
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table)) {
+		r = PTR_ERR(opp_table);
+		dev_warn(dev, "%s: Device OPP not found (%d)\n", __func__, r);
+		return r;
+	}
+
+	/* keep the node allocated */
+	new_opp = kmalloc(sizeof(*new_opp), GFP_KERNEL);
+	if (!new_opp)
+		return -ENOMEM;
+
+	mutex_lock(&opp_table->lock);
+
+	/* Do we have the frequency? */
+	list_for_each_entry(tmp_opp, &opp_table->opp_list, node) {
+		if (tmp_opp->rate == freq) {
+			opp = tmp_opp;
+			break;
+		}
+	}
+
+	if (IS_ERR(opp)) {
+		r = PTR_ERR(opp);
+		goto unlock;
+	}
+
+	/* Is update really needed? */
+	if (opp->supplies->u_volt == u_volt)
+		goto unlock;
+
+	/* copy the old data over */
+	*new_opp = *opp;
+
+	/* plug in new node */
+	new_opp->supplies->u_volt = u_volt;
+
+	list_replace_rcu(&opp->node, &new_opp->node);
+	mutex_unlock(&opp_table->lock);
+
+	/* Notify the change of the OPP */
+	blocking_notifier_call_chain(&opp_table->head, OPP_EVENT_ADJUST_VOLTAGE,
+				     opp);
+
+	return 0;
+
+unlock:
+	mutex_unlock(&opp_table->lock);
+	kfree(new_opp);
+	return r;
+}
+
 /**
  * dev_pm_opp_enable() - Enable a specific OPP
  * @dev:	device for which we do this operation
diff --git a/include/linux/pm_opp.h b/include/linux/pm_opp.h
index 24c757a32a7b..70219fe3ca20 100644
--- a/include/linux/pm_opp.h
+++ b/include/linux/pm_opp.h
@@ -25,6 +25,7 @@  struct opp_table;
 
 enum dev_pm_opp_event {
 	OPP_EVENT_ADD, OPP_EVENT_REMOVE, OPP_EVENT_ENABLE, OPP_EVENT_DISABLE,
+	OPP_EVENT_ADJUST_VOLTAGE,
 };
 
 /**
@@ -112,6 +113,9 @@  int dev_pm_opp_add(struct device *dev, unsigned long freq,
 void dev_pm_opp_remove(struct device *dev, unsigned long freq);
 void dev_pm_opp_remove_all_dynamic(struct device *dev);
 
+int dev_pm_opp_adjust_voltage(struct device *dev, unsigned long freq,
+			      unsigned long u_volt);
+
 int dev_pm_opp_enable(struct device *dev, unsigned long freq);
 
 int dev_pm_opp_disable(struct device *dev, unsigned long freq);
@@ -229,6 +233,13 @@  static inline void dev_pm_opp_remove_all_dynamic(struct device *dev)
 {
 }
 
+static inline int
+dev_pm_opp_adjust_voltage(struct device *dev, unsigned long freq,
+			  unsigned long u_volt)
+{
+	return 0;
+}
+
 static inline int dev_pm_opp_enable(struct device *dev, unsigned long freq)
 {
 	return 0;