diff mbox series

[RFC,1/2] PM: domains: Allow devices attached to genpd to be managed by HW

Message ID 20230627104033.3345659-1-abel.vesa@linaro.org (mailing list archive)
State RFC, archived
Headers show
Series [RFC,1/2] PM: domains: Allow devices attached to genpd to be managed by HW | expand

Commit Message

Abel Vesa June 27, 2023, 10:40 a.m. UTC 
From: Ulf Hansson <ulf.hansson@linaro.org>

Some power-domains may be capable of relying on the HW to control the power
for a device that's hooked up to it. Typically, for these kinds of
configurations the device doesn't really need to be attached to a PM domain
(genpd), from Linux point of view. However, in some cases the behaviour of
the power-domain and its device can be changed in runtime.

To allow a consumer driver to change the behaviour of the PM domain for its
device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
which the genpd provider should implement if it can support switching
between HW controlled mode and SW controlled mode.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/base/power/domain.c | 66 +++++++++++++++++++++++++++++++++++++
 include/linux/pm_domain.h   | 15 +++++++++
 2 files changed, 81 insertions(+)

Comments

Greg KH June 27, 2023, 10:46 a.m. UTC | #1 
On Tue, Jun 27, 2023 at 01:40:32PM +0300, Abel Vesa wrote:
> From: Ulf Hansson <ulf.hansson@linaro.org>
> 
> Some power-domains may be capable of relying on the HW to control the power
> for a device that's hooked up to it. Typically, for these kinds of
> configurations the device doesn't really need to be attached to a PM domain
> (genpd), from Linux point of view. However, in some cases the behaviour of
> the power-domain and its device can be changed in runtime.
> 
> To allow a consumer driver to change the behaviour of the PM domain for its
> device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
> let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
> which the genpd provider should implement if it can support switching
> between HW controlled mode and SW controlled mode.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

You can't forward on a patch from someone else without also adding your
signed-off-by on it, right?

Also, why is this a RFC series?  What is left to do with it to get it
into a state which you feel comfortable having us review it "for real"?

thanks,

greg k-h
Abel Vesa June 27, 2023, 10:54 a.m. UTC | #2 
On 23-06-27 12:46:28, Greg Kroah-Hartman wrote:
> On Tue, Jun 27, 2023 at 01:40:32PM +0300, Abel Vesa wrote:
> > From: Ulf Hansson <ulf.hansson@linaro.org>
> > 
> > Some power-domains may be capable of relying on the HW to control the power
> > for a device that's hooked up to it. Typically, for these kinds of
> > configurations the device doesn't really need to be attached to a PM domain
> > (genpd), from Linux point of view. However, in some cases the behaviour of
> > the power-domain and its device can be changed in runtime.
> > 
> > To allow a consumer driver to change the behaviour of the PM domain for its
> > device, let's provide a new function, dev_pm_genpd_set_hwmode(). Moreover,
> > let's add a corresponding optional genpd callback, ->set_hwmode_dev(),
> > which the genpd provider should implement if it can support switching
> > between HW controlled mode and SW controlled mode.
> > 
> > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> 
> You can't forward on a patch from someone else without also adding your
> signed-off-by on it, right?

Oups, forgot to add it. Will do in the next version.

> 
> Also, why is this a RFC series?  What is left to do with it to get it
> into a state which you feel comfortable having us review it "for real"?

There is a bit of back story here. This HW control support is something
that Qualcomm platforms support for some of the PDs. Sent this as RFC
as I thought it might open up a discussion of such a generic need at
first. But now that I think of it, it might've been a non-RFC patch as
well.

> 
> thanks,
> 
> greg k-h
Greg KH June 27, 2023, 11:02 a.m. UTC | #3 
On Tue, Jun 27, 2023 at 01:54:06PM +0300, Abel Vesa wrote:
> On 23-06-27 12:46:28, Greg Kroah-Hartman wrote:
> > Also, why is this a RFC series?  What is left to do with it to get it
> > into a state which you feel comfortable having us review it "for real"?
> 
> There is a bit of back story here. This HW control support is something
> that Qualcomm platforms support for some of the PDs. Sent this as RFC
> as I thought it might open up a discussion of such a generic need at
> first. But now that I think of it, it might've been a non-RFC patch as
> well.

You need to provide that information, otherwise what are we supposed to
do with this patch series?  What would you do if you got it in your
inbox?

thanks,

greg k-h
Abel Vesa June 27, 2023, 11:48 a.m. UTC | #4 
On 23-06-27 13:02:50, Greg Kroah-Hartman wrote:
> On Tue, Jun 27, 2023 at 01:54:06PM +0300, Abel Vesa wrote:
> > On 23-06-27 12:46:28, Greg Kroah-Hartman wrote:
> > > Also, why is this a RFC series?  What is left to do with it to get it
> > > into a state which you feel comfortable having us review it "for real"?
> > 
> > There is a bit of back story here. This HW control support is something
> > that Qualcomm platforms support for some of the PDs. Sent this as RFC
> > as I thought it might open up a discussion of such a generic need at
> > first. But now that I think of it, it might've been a non-RFC patch as
> > well.
> 
> You need to provide that information, otherwise what are we supposed to
> do with this patch series?  What would you do if you got it in your
> inbox?

Will do in the next version.

Thanks.

> 
> thanks,
> 
> greg k-h
diff mbox series

Patch

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 5cb2023581d4..23286853d1d0 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -541,6 +541,72 @@  void dev_pm_genpd_synced_poweroff(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dev_pm_genpd_synced_poweroff);
 
+/**
+ * dev_pm_genpd_set_hwmode - Set the HW mode for the device and its PM domain.
+ *
+ * @dev: Device for which the HW-mode should be changed.
+ * @enable: Value to set or unset the HW-mode.
+ *
+ * Some PM domains can rely on HW signals to control the power for a device. To
+ * allow a consumer driver to switch the behaviour for its device in runtime,
+ * which may be beneficial from a latency or energy point of view, this function
+ * may be called.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ *
+ * Returns 0 on success and negative error values on failures.
+ */
+int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
+{
+	struct generic_pm_domain *genpd;
+	int ret = 0;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return -ENODEV;
+
+	if (!genpd->set_hwmode_dev)
+		return -EOPNOTSUPP;
+
+	genpd_lock(genpd);
+
+	if (dev_gpd_data(dev)->hw_mode == enable)
+		goto out;
+
+	ret = genpd->set_hwmode_dev(genpd, dev, enable);
+	if (!ret)
+		dev_gpd_data(dev)->hw_mode = enable;
+
+out:
+	genpd_unlock(genpd);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_set_hwmode);
+
+/**
+ * dev_pm_genpd_get_hwmode - Get the HW mode setting for the device.
+ *
+ * @dev: Device for which the current HW-mode setting should be fetched.
+ *
+ * This helper function allows consumer drivers to fetch the current HW mode
+ * setting of its the device.
+ *
+ * It is assumed that the users guarantee that the genpd wouldn't be detached
+ * while this routine is getting called.
+ */
+bool dev_pm_genpd_get_hwmode(struct device *dev)
+{
+	struct generic_pm_domain *genpd;
+
+	genpd = dev_to_genpd_safe(dev);
+	if (!genpd)
+		return false;
+
+	return dev_gpd_data(dev)->hw_mode;
+}
+EXPORT_SYMBOL_GPL(dev_pm_genpd_get_hwmode);
+
 static int _genpd_power_on(struct generic_pm_domain *genpd, bool timed)
 {
 	unsigned int state_idx = genpd->state_idx;
diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
index f776fb93eaa0..8f60c36851d5 100644
--- a/include/linux/pm_domain.h
+++ b/include/linux/pm_domain.h
@@ -146,6 +146,8 @@  struct generic_pm_domain {
 	int (*set_performance_state)(struct generic_pm_domain *genpd,
 				     unsigned int state);
 	struct gpd_dev_ops dev_ops;
+	int (*set_hwmode_dev)(struct generic_pm_domain *domain,
+			      struct device *dev, bool enable);
 	int (*attach_dev)(struct generic_pm_domain *domain,
 			  struct device *dev);
 	void (*detach_dev)(struct generic_pm_domain *domain,
@@ -208,6 +210,7 @@  struct generic_pm_domain_data {
 	unsigned int performance_state;
 	unsigned int default_pstate;
 	unsigned int rpm_pstate;
+	bool hw_mode;
 	void *data;
 };
 
@@ -237,6 +240,8 @@  int dev_pm_genpd_remove_notifier(struct device *dev);
 void dev_pm_genpd_set_next_wakeup(struct device *dev, ktime_t next);
 ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev);
 void dev_pm_genpd_synced_poweroff(struct device *dev);
+int dev_pm_genpd_set_hwmode(struct device *dev, bool enable);
+bool dev_pm_genpd_get_hwmode(struct device *dev);
 
 extern struct dev_power_governor simple_qos_governor;
 extern struct dev_power_governor pm_domain_always_on_gov;
@@ -305,6 +310,16 @@  static inline ktime_t dev_pm_genpd_get_next_hrtimer(struct device *dev)
 static inline void dev_pm_genpd_synced_poweroff(struct device *dev)
 { }
 
+static inline int dev_pm_genpd_set_hwmode(struct device *dev, bool enable)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline bool dev_pm_genpd_get_hwmode(struct device *dev)
+{
+	return false;
+}
+
 #define simple_qos_governor		(*(struct dev_power_governor *)(NULL))
 #define pm_domain_always_on_gov		(*(struct dev_power_governor *)(NULL))
 #endif