clk: scmi: Add support for .is_enabled clk_ops

Add support for .is_enabled atomic clk_ops using the related SCMI clock
operation in atomic mode, if available.

Note that the .is_enabled callback will be supported by this SCMI clock
driver only if the configured underlying SCMI transport does support atomic
operations.

CC: Michael Turquette <mturquette@baylibre.com>
CC: Stephen Boyd <sboyd@kernel.org>
CC: linux-clk@vger.kernel.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20230826125308.462328-6-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/clk/clk-scmi.c

@@ -20,6 +20,7 @@ static const struct scmi_clk_proto_ops *scmi_proto_clk_ops;
 
 struct scmi_clk {
 	u32 id;
+	struct device *dev;
 	struct clk_hw hw;
 	const struct scmi_clock_info *info;
 	const struct scmi_protocol_handle *ph;
@@ -105,10 +106,24 @@ static void scmi_clk_atomic_disable(struct clk_hw *hw)
 	scmi_proto_clk_ops->disable(clk->ph, clk->id, ATOMIC);
 }
 
+static int scmi_clk_atomic_is_enabled(struct clk_hw *hw)
+{
+	int ret;
+	bool enabled = false;
+	struct scmi_clk *clk = to_scmi_clk(hw);
+
+	ret = scmi_proto_clk_ops->state_get(clk->ph, clk->id, &enabled, ATOMIC);
+	if (ret)
+		dev_warn(clk->dev,
+			 "Failed to get state for clock ID %d\n", clk->id);
+
+	return !!enabled;
+}
+
 /*
- * We can provide enable/disable atomic callbacks only if the underlying SCMI
- * transport for an SCMI instance is configured to handle SCMI commands in an
- * atomic manner.
+ * We can provide enable/disable/is_enabled atomic callbacks only if the
+ * underlying SCMI transport for an SCMI instance is configured to handle
+ * SCMI commands in an atomic manner.
  *
  * When no SCMI atomic transport support is available we instead provide only
  * the prepare/unprepare API, as allowed by the clock framework when atomic
@@ -132,6 +147,7 @@ static const struct clk_ops scmi_atomic_clk_ops = {
 	.set_rate = scmi_clk_set_rate,
 	.enable = scmi_clk_atomic_enable,
 	.disable = scmi_clk_atomic_disable,
+	.is_enabled = scmi_clk_atomic_is_enabled,
 };
 
 static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk,
@@ -221,6 +237,7 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 
 		sclk->id = idx;
 		sclk->ph = ph;
+		sclk->dev = dev;
 
 		/*
 		 * Note that when transport is atomic but SCMI protocol did not