clk: scmi: Add support for rate change restricted clocks

Some exposed SCMI Clocks could be marked as non-supporting rate changes.
Configure a clk_ops descriptors which does not provide the rate change
callbacks for such clocks when registering with CLK framework.

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>
Link: https://lore.kernel.org/r/20240415163649.895268-4-cristian.marussi@arm.comReviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk-scmi.c

@@ -20,6 +20,7 @@
 enum scmi_clk_feats {
 	SCMI_CLK_ATOMIC_SUPPORTED,
 	SCMI_CLK_STATE_CTRL_SUPPORTED,
+	SCMI_CLK_RATE_CTRL_SUPPORTED,
 	SCMI_CLK_FEATS_COUNT
 };
 
@@ -248,6 +249,7 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
 	ops->recalc_rate = scmi_clk_recalc_rate;
 	ops->round_rate = scmi_clk_round_rate;
 	ops->determine_rate = scmi_clk_determine_rate;
+	if (feats_key & BIT(SCMI_CLK_RATE_CTRL_SUPPORTED))
 		ops->set_rate = scmi_clk_set_rate;
 
 	/* Parent ops */
@@ -302,6 +304,9 @@ scmi_clk_ops_select(struct scmi_clk *sclk, bool atomic_capable,
 	if (!ci->state_ctrl_forbidden)
 		feats_key |= BIT(SCMI_CLK_STATE_CTRL_SUPPORTED);
 
+	if (!ci->rate_ctrl_forbidden)
+		feats_key |= BIT(SCMI_CLK_RATE_CTRL_SUPPORTED);
+
 	if (WARN_ON(feats_key >= db_size))
 		return NULL;