Hi Ulf,
Thanks for your comments!
On 2016-10-07 12:07, Ulf Hansson wrote:
On 19 September 2016 at 12:55, Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
Registers for some clocks might be located in the SOC area, which are under the
power domain. To enable access to those registers respective domain has to be
turned on. Additionally, registers for such clocks will usually loose its
contents when power domain is turned off, so additional saving and restoring of
them might be needed in the clock controller driver.
This patch adds basic infrastructure in the clocks core to allow implementing
driver for such clocks under power domains. Clock provider can supply a
struct device pointer, which is the used by clock core for tracking and managing
clock's controller runtime pm state. Each clk_prepare() operation
will first call pm_runtime_get_sync() on the supplied device, while
clk_unprepare() will do pm_runtime_put() at the end.
Additional calls to pm_runtime_get/put functions are required to ensure that any
register access (like calculating/changing clock rates and unpreparing/disabling
unused clocks on boot) will be done with clock controller in runtime resumend
state.
When one wants to register clock controller, which make use of this feature, he
has to:
1. Provide a struct device to the core when registering the provider and set
CLK_RUNTIME_PM flags for its clocks.
2. It needs to enable runtime PM for that device.
3. It needs to make sure the runtime PM status of the controller device reflects
the HW state.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
drivers/clk/clk.c | 107 +++++++++++++++++++++++++++++++++++++++----
include/linux/clk-provider.h | 1 +
2 files changed, 98 insertions(+), 10 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 820a939fb6bb..096a199b8e46 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -21,6 +21,7 @@
#include <linux/of.h>
#include <linux/device.h>
#include <linux/init.h>
+#include <linux/pm_runtime.h>
#include <linux/sched.h>
#include <linux/clkdev.h>
@@ -46,6 +47,7 @@ struct clk_core {
const struct clk_ops *ops;
struct clk_hw *hw;
struct module *owner;
+ struct device *dev;
struct clk_core *parent;
const char **parent_names;
struct clk_core **parents;
@@ -87,6 +89,26 @@ struct clk {
struct hlist_node clks_node;
};
+/*** runtime pm ***/
+static int clk_pm_runtime_get(struct clk_core *core)
+{
+ int ret = 0;
+
+ if (!core->dev)
+ return 0;
+
+ ret = pm_runtime_get_sync(core->dev);
+ return ret < 0 ? ret : 0;
+}
+
+static void clk_pm_runtime_put(struct clk_core *core)
+{
+ if (!core->dev)
+ return;
+
+ pm_runtime_put(core->dev);
+}
+
/*** locking ***/
static void clk_prepare_lock(void)
{
@@ -150,6 +172,8 @@ static void clk_enable_unlock(unsigned long flags)
static bool clk_core_is_prepared(struct clk_core *core)
{
+ bool status;
+
/*
* .is_prepared is optional for clocks that can prepare
* fall back to software usage counter if it is missing
@@ -157,11 +181,17 @@ static bool clk_core_is_prepared(struct clk_core *core)
if (!core->ops->is_prepared)
return core->prepare_count;
- return core->ops->is_prepared(core->hw);
+ clk_pm_runtime_get(core);
I guess you should assign status to the return code, and check it.
Okay. I assume that in case of any failure from runtime pm, the function
should return false?
+ status = core->ops->is_prepared(core->hw);
+ clk_pm_runtime_put(core);
+
+ return status;
}
static bool clk_core_is_enabled(struct clk_core *core)
{
+ bool status;
+
/*
* .is_enabled is only mandatory for clocks that gate
* fall back to software usage counter if .is_enabled is missing
@@ -169,7 +199,29 @@ static bool clk_core_is_enabled(struct clk_core *core)
if (!core->ops->is_enabled)
return core->enable_count;
- return core->ops->is_enabled(core->hw);
+ /*
+ * Check if runtime pm is enabled before calling .is_enabled callback,
+ * if not assume that clock is disabled, because we might be called
+ * from atomic context, from which pm_runtime_get() is not allowed.
+ * This function is called mainly from clk_disable_unused_subtree,
+ * which ensures proper runtime pm activation of controller before
+ * taking enable spinlock, but the below check is needed if one tries
+ * to call it from other place.
+ */
+ if (core->dev) {
+ pm_runtime_get_noresume(core->dev);
+ if (pm_runtime_suspended(core->dev)) {
I think it's wrong to use pm_runtime_suspended().
What you should be checking, is whether the device is RPM_ACTIVE or if
runtime PM isn't enabled for device.
In other words, you should use pm_runtime_active() to find out whether
it's okay to invoke the ->is_enabled() ops or not.
Accordingly, I think the upper comment you added then needs to be a
rephrased a bit to reflect this.
Okay, I will change it to use pm_runtime_active(). It looks that mentally
I still assume that runtime pm will be disabled in system sleep transitions
phase, so the only check that provided some useful information about
previous runtime pm state was pm_runtime_suspended().
+ status = false;
+ goto done;
+ }
+ }
+
+ status = core->ops->is_enabled(core->hw);
+done:
+ if (core->dev)
+ pm_runtime_put(core->dev);
+
+ return status;
}
/*** helper functions ***/
@@ -489,6 +541,8 @@ static void clk_core_unprepare(struct clk_core *core)
if (core->ops->unprepare)
core->ops->unprepare(core->hw);
+ clk_pm_runtime_put(core);
+
trace_clk_unprepare_complete(core);
clk_core_unprepare(core->parent);
}
@@ -530,10 +584,14 @@ static int clk_core_prepare(struct clk_core *core)
return 0;
if (core->prepare_count == 0) {
- ret = clk_core_prepare(core->parent);
+ ret = clk_pm_runtime_get(core);
if (ret)
return ret;
+ ret = clk_core_prepare(core->parent);
+ if (ret)
+ goto runtime_put;
+
trace_clk_prepare(core);
if (core->ops->prepare)
@@ -541,15 +599,18 @@ static int clk_core_prepare(struct clk_core *core)
trace_clk_prepare_complete(core);
- if (ret) {
- clk_core_unprepare(core->parent);
- return ret;
- }
+ if (ret)
+ goto unprepare;
}
core->prepare_count++;
return 0;
+unprepare:
+ clk_core_unprepare(core->parent);
+runtime_put:
+ clk_pm_runtime_put(core);
+ return ret;
}
static int clk_core_prepare_lock(struct clk_core *core)
@@ -745,6 +806,9 @@ static void clk_unprepare_unused_subtree(struct clk_core *core)
if (core->flags & CLK_IGNORE_UNUSED)
return;
+ if (clk_pm_runtime_get(core) != 0)
You may simplify this:
if (clk_pm_runtime_get(core))
+ return;
+
if (clk_core_is_prepared(core)) {
trace_clk_unprepare(core);
if (core->ops->unprepare_unused)
@@ -753,6 +817,8 @@ static void clk_unprepare_unused_subtree(struct clk_core *core)
core->ops->unprepare(core->hw);
trace_clk_unprepare_complete(core);
}
+
+ clk_pm_runtime_put(core);
}
static void clk_disable_unused_subtree(struct clk_core *core)
@@ -768,6 +834,9 @@ static void clk_disable_unused_subtree(struct clk_core *core)
if (core->flags & CLK_OPS_PARENT_ENABLE)
clk_core_prepare_enable(core->parent);
+ if (clk_pm_runtime_get(core) != 0)
Is there any reason to why you haven't moved this further down in this
function, like just before calling clk_core_is_enabled()?
Yes, clk_enable_lock() takes a spinlock, so I cannot call pm_runtime_get
after it.
You may also simplify this:
if (clk_pm_runtime_get(core))
+ return;
+
You need to restore the call made to clk_core_prepare_enable()
earlier, so please update the error handling to cope with this.
flags = clk_enable_lock();
if (core->enable_count)
@@ -794,6 +863,8 @@ unlock_out:
clk_enable_unlock(flags);
if (core->flags & CLK_OPS_PARENT_ENABLE)
clk_core_disable_unprepare(core->parent);
+
+ clk_pm_runtime_put(core);
}
static bool clk_ignore_unused;
@@ -1563,6 +1634,7 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
{
struct clk_core *top, *fail_clk;
unsigned long rate = req_rate;
+ int ret = 0;
if (!core)
return 0;
@@ -1579,21 +1651,28 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
if (!top)
return -EINVAL;
+ ret = clk_pm_runtime_get(core);
+ if (ret)
+ return ret;
+
/* notify that we are about to change rates */
fail_clk = clk_propagate_rate_change(top, PRE_RATE_CHANGE);
if (fail_clk) {
pr_debug("%s: failed to set %s rate\n", __func__,
fail_clk->name);
clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
- return -EBUSY;
+ ret = -EBUSY;
+ goto err;
}
/* change the rates */
clk_change_rate(top);
core->req_rate = req_rate;
+err:
+ clk_pm_runtime_put(core);
- return 0;
+ return ret;
}
/**
@@ -1824,12 +1903,16 @@ static int clk_core_set_parent(struct clk_core *core, struct clk_core *parent)
p_rate = parent->rate;
}
+ ret = clk_pm_runtime_get(core);
+ if (ret)
+ goto out;
+
/* propagate PRE_RATE_CHANGE notifications */
ret = __clk_speculate_rates(core, p_rate);
/* abort if a driver objects */
if (ret & NOTIFY_STOP_MASK)
- goto out;
+ goto runtime_put;
/* do the re-parent */
ret = __clk_set_parent(core, parent, p_index);
@@ -1842,6 +1925,8 @@ static int clk_core_set_parent(struct clk_core *core, struct clk_core *parent)
__clk_recalc_accuracies(core);
}
+runtime_put:
+ clk_pm_runtime_put(core);
out:
clk_prepare_unlock();
@@ -2546,6 +2631,8 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw)
goto fail_name;
}
core->ops = hw->init->ops;
+ if (dev && (hw->init->flags & CLK_RUNTIME_PM))
+ core->dev = dev;
I guess you need this to play safe, although I am really wondering if
we should try without.
Not that many clocks are currently being registered with a valid
struct device pointer. For the other cases why not try to use runtime
PM as per default?
I've that tried initially, but it causes failure for all the clock
controllers, which don't enable runtime pm. One of such case is max77686
PMIC, which provides 3 clocks. Maybe a negative flag (CLK_NO_RUNTIME_PM)
will be a better solution, so by default the runtime pm calls will be
enabled for every driver providing struct device?
Moreover we anyway rely on the clock provider to enable runtime PM for
the clock device, and when that isn't the case the runtime PM
deployment in the core should still be safe, right!?
I don't get the above comment. Do you want to check if runtime pm has
been enabled during clock registration?
if (dev && dev->driver)
core->owner = dev->driver->owner;
core->hw = hw;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index a39c0c530778..8a131eb71fdf 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -35,6 +35,7 @@
#define CLK_IS_CRITICAL BIT(11) /* do not gate, ever */
/* parents need enable during gate/ungate, set rate and re-parent */
#define CLK_OPS_PARENT_ENABLE BIT(12)
+#define CLK_RUNTIME_PM BIT(13)
struct clk;
struct clk_hw;
--
1.9.1
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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