Some platforms require clock to be always running, e.g. because those clock
supply devices which are not otherwise attached to the system. One example
is a system where the SoC serves as a crystal oscillator replacement for a
programmable logic device. The critical-clock property of a clock controller
allows listing clock which must never be turned off.
The implementation here is similar to "protected-clock", except protected
clock property is currently driver specific. This patch attempts to make
a generic implementation of "critical-clock" instead.
Unlike "assigned-clocks", the "critical-clock" must be parsed much earlier
in __clk_register() to assign CLK_IS_CRITICAL flag to clk_init_data .flags
field. The parsing code obviously need to be cleaned up and factor out into
separate function.
The new match_clkspec() callback is used to determine whether struct clk_hw
that is currently being registered matches the clock specifier in the DT
"critical-clock" property, and if so, then the CLK_IS_CRITICAL is added to
these newly registered clock. This callback is currently driver specific,
although I suspect a common and/or generic version of the callback could
be added. Also, this new callback could possibly be used to replace (*get)
argument of of_clk_add_hw_provider() later on too.
Signed-off-by: Marek Vasut <marex@xxxxxxx>
Cc: Matti Vaittinen <matti.vaittinen@xxxxxxxxxxxxxxxxx>
Cc: Michael Turquette <mturquette@xxxxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
Cc: devicetree@xxxxxxxxxxxxxxx
Cc: linux-power@xxxxxxxxxxxxxxxxx
To: linux-clk@xxxxxxxxxxxxxxx
---
drivers/clk/clk.c | 41 ++++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 3 +++
2 files changed, 44 insertions(+)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8de6a22498e70..1e1686fa76e01 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3872,6 +3872,45 @@ static void clk_core_free_parent_map(struct clk_core *core)
kfree(core->parents);
}
+static void
+__clk_register_critical_clock(struct device_node *np, struct clk_core *core,
+ struct clk_hw *hw)
+{
+ struct of_phandle_args clkspec;
+ u32 clksize, clktotal;
+ int ret, i, index;
+
+ if (!np)
+ return;
+
+ if (!core->ops->match_clkspec)
+ return;
+
+ if (of_property_read_u32(np, "#clock-cells", &clksize))
+ return;
+
+ /* Clock node with #clock-cells = <0> uses critical-clocks; */
+ if (clksize == 0) {
+ if (of_property_read_bool(np, "critical-clocks") &&
+ !core->ops->match_clkspec(hw, &clkspec))
+ core->flags |= CLK_IS_CRITICAL;
+ return;
+ }
+
+ clkspec.np = np;
+ clktotal = of_property_count_u32_elems(np, "critical-clocks");
+ clktotal /= clksize;
+ for (index = 0; index < clktotal; index++) {
+ for (i = 0; i < clksize; i++) {
+ ret = of_property_read_u32_index(np, "critical-clocks",
+ (index * clksize) + i,
+ &(clkspec.args[i]));
+ }
+ if (!core->ops->match_clkspec(hw, &clkspec))
+ core->flags |= CLK_IS_CRITICAL;
+ }
+}
+
static struct clk *
__clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
{
@@ -3916,6 +3955,8 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
core->min_rate = 0;
core->max_rate = ULONG_MAX;
+ __clk_register_critical_clock(np, core, hw);
+
ret = clk_core_populate_parent_map(core, init);
if (ret)
goto fail_parents;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 2faa6f7aa8a87..8bc0eedfeb2fd 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -205,6 +205,8 @@ struct clk_duty {
* directory is provided as an argument. Called with
* prepare_lock held. Returns 0 on success, -EERROR otherwise.
*
+ * @match_clkspec: Check whether clk_hw matches DT clock specifier.
+ * Returns 0 on success, -EERROR otherwise.
*
* The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
* implementations to split any work between atomic (enable) and sleepable
@@ -252,6 +254,7 @@ struct clk_ops {
int (*init)(struct clk_hw *hw);
void (*terminate)(struct clk_hw *hw);
void (*debug_init)(struct clk_hw *hw, struct dentry *dentry);
+ int (*match_clkspec)(struct clk_hw *hw, struct of_phandle_args *clkspec);
};
/**
--
2.34.1
