firmware: arm_scmi: Add support for clock parents

SCMI v3.2 spec introduces CLOCK_POSSIBLE_PARENTS_GET, CLOCK_PARENT_SET
and CLOCK_PARENT_GET. Add support for these to enable clock parents
and use them in the clock driver.

Reviewed-by: Cristian Marussi <[e-mail]>
Signed-off-by: Peng Fan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sudeep Holla <[e-mail]>

drivers/firmware/arm_scmi/clock.c

···
 	CLOCK_RATE_NOTIFY = 0x9,
 	CLOCK_RATE_CHANGE_REQUESTED_NOTIFY = 0xA,
 	CLOCK_CONFIG_GET = 0xB,
+	CLOCK_POSSIBLE_PARENTS_GET = 0xC,
+	CLOCK_PARENT_SET = 0xD,
+	CLOCK_PARENT_GET = 0xE,
 };
 
 enum clk_state {
···
 #define SUPPORTS_RATE_CHANGED_NOTIF(x)		((x) & BIT(31))
 #define SUPPORTS_RATE_CHANGE_REQUESTED_NOTIF(x)	((x) & BIT(30))
 #define SUPPORTS_EXTENDED_NAMES(x)		((x) & BIT(29))
+#define SUPPORTS_PARENT_CLOCK(x)		((x) & BIT(28))
 	u8 name[SCMI_SHORT_NAME_MAX_SIZE];
 	__le32 clock_enable_latency;
+};
+
+struct scmi_msg_clock_possible_parents {
+	__le32 id;
+	__le32 skip_parents;
+};
+
+struct scmi_msg_resp_clock_possible_parents {
+	__le32 num_parent_flags;
+#define NUM_PARENTS_RETURNED(x)		((x) & 0xff)
+#define NUM_PARENTS_REMAINING(x)	((x) >> 24)
+	__le32 possible_parents[];
+};
+
+struct scmi_msg_clock_set_parent {
+	__le32 id;
+	__le32 parent_id;
 };
 
 struct scmi_msg_clock_config_set {
···
 	return ret;
 }
 
+struct scmi_clk_ipriv {
+	struct device *dev;
+	u32 clk_id;
+	struct scmi_clock_info *clk;
+};
+
+static void iter_clk_possible_parents_prepare_message(void *message, unsigned int desc_index,
+						      const void *priv)
+{
+	struct scmi_msg_clock_possible_parents *msg = message;
+	const struct scmi_clk_ipriv *p = priv;
+
+	msg->id = cpu_to_le32(p->clk_id);
+	/* Set the number of OPPs to be skipped/already read */
+	msg->skip_parents = cpu_to_le32(desc_index);
+}
+
+static int iter_clk_possible_parents_update_state(struct scmi_iterator_state *st,
+						  const void *response, void *priv)
+{
+	const struct scmi_msg_resp_clock_possible_parents *r = response;
+	struct scmi_clk_ipriv *p = priv;
+	struct device *dev = ((struct scmi_clk_ipriv *)p)->dev;
+	u32 flags;
+
+	flags = le32_to_cpu(r->num_parent_flags);
+	st->num_returned = NUM_PARENTS_RETURNED(flags);
+	st->num_remaining = NUM_PARENTS_REMAINING(flags);
+
+	/*
+	 * num parents is not declared previously anywhere so we
+	 * assume it's returned+remaining on first call.
+	 */
+	if (!st->max_resources) {
+		p->clk->num_parents = st->num_returned + st->num_remaining;
+		p->clk->parents = devm_kcalloc(dev, p->clk->num_parents,
+					       sizeof(*p->clk->parents),
+					       GFP_KERNEL);
+		if (!p->clk->parents) {
+			p->clk->num_parents = 0;
+			return -ENOMEM;
+		}
+		st->max_resources = st->num_returned + st->num_remaining;
+	}
+
+	return 0;
+}
+
+static int iter_clk_possible_parents_process_response(const struct scmi_protocol_handle *ph,
+						      const void *response,
+						      struct scmi_iterator_state *st,
+						      void *priv)
+{
+	const struct scmi_msg_resp_clock_possible_parents *r = response;
+	struct scmi_clk_ipriv *p = priv;
+
+	u32 *parent = &p->clk->parents[st->desc_index + st->loop_idx];
+
+	*parent = le32_to_cpu(r->possible_parents[st->loop_idx]);
+
+	return 0;
+}
+
+static int scmi_clock_possible_parents(const struct scmi_protocol_handle *ph, u32 clk_id,
+				       struct scmi_clock_info *clk)
+{
+	struct scmi_iterator_ops ops = {
+		.prepare_message = iter_clk_possible_parents_prepare_message,
+		.update_state = iter_clk_possible_parents_update_state,
+		.process_response = iter_clk_possible_parents_process_response,
+	};
+
+	struct scmi_clk_ipriv ppriv = {
+		.clk_id = clk_id,
+		.clk = clk,
+		.dev = ph->dev,
+	};
+	void *iter;
+	int ret;
+
+	iter = ph->hops->iter_response_init(ph, &ops, 0,
+					    CLOCK_POSSIBLE_PARENTS_GET,
+					    sizeof(struct scmi_msg_clock_possible_parents),
+					    &ppriv);
+	if (IS_ERR(iter))
+		return PTR_ERR(iter);
+
+	ret = ph->hops->iter_response_run(iter);
+
+	return ret;
+}
+
 static int scmi_clock_attributes_get(const struct scmi_protocol_handle *ph,
 				     u32 clk_id, struct scmi_clock_info *clk,
 				     u32 version)
···
 			clk->rate_changed_notifications = true;
 		if (SUPPORTS_RATE_CHANGE_REQUESTED_NOTIF(attributes))
 			clk->rate_change_requested_notifications = true;
+		if (SUPPORTS_PARENT_CLOCK(attributes))
+			scmi_clock_possible_parents(ph, clk_id, clk);
 	}
 
 	return ret;
···
 	else
 		return 1;
 }
-
-struct scmi_clk_ipriv {
-	struct device *dev;
-	u32 clk_id;
-	struct scmi_clock_info *clk;
-};
 
 static void iter_clk_describe_prepare_message(void *message,
 					      const unsigned int desc_index,
···
 	return ret;
 }
 
+static int
+scmi_clock_set_parent(const struct scmi_protocol_handle *ph, u32 clk_id,
+		      u32 parent_id)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_msg_clock_set_parent *cfg;
+	struct clock_info *ci = ph->get_priv(ph);
+	struct scmi_clock_info *clk;
+
+	if (clk_id >= ci->num_clocks)
+		return -EINVAL;
+
+	clk = ci->clk + clk_id;
+
+	if (parent_id >= clk->num_parents)
+		return -EINVAL;
+
+	ret = ph->xops->xfer_get_init(ph, CLOCK_PARENT_SET,
+				      sizeof(*cfg), 0, &t);
+	if (ret)
+		return ret;
+
+	t->hdr.poll_completion = false;
+
+	cfg = t->tx.buf;
+	cfg->id = cpu_to_le32(clk_id);
+	cfg->parent_id = cpu_to_le32(clk->parents[parent_id]);
+
+	ret = ph->xops->do_xfer(ph, t);
+
+	ph->xops->xfer_put(ph, t);
+
+	return ret;
+}
+
+static int
+scmi_clock_get_parent(const struct scmi_protocol_handle *ph, u32 clk_id,
+		      u32 *parent_id)
+{
+	int ret;
+	struct scmi_xfer *t;
+
+	ret = ph->xops->xfer_get_init(ph, CLOCK_PARENT_GET,
+				      sizeof(__le32), sizeof(u32), &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(clk_id, t->tx.buf);
+
+	ret = ph->xops->do_xfer(ph, t);
+	if (!ret)
+		*parent_id = get_unaligned_le32(t->rx.buf);
+
+	ph->xops->xfer_put(ph, t);
+	return ret;
+}
+
 /* For SCMI clock v2.1 and onwards */
 static int
 scmi_clock_config_set_v2(const struct scmi_protocol_handle *ph, u32 clk_id,
···
 	.state_get = scmi_clock_state_get,
 	.config_oem_get = scmi_clock_config_oem_get,
 	.config_oem_set = scmi_clock_config_oem_set,
+	.parent_set = scmi_clock_set_parent,
+	.parent_get = scmi_clock_get_parent,
 };
 
 static int scmi_clk_rate_notify(const struct scmi_protocol_handle *ph,

include/linux/scmi_protocol.h

···
 			u64 step_size;
 		} range;
 	};
+	int num_parents;
+	u32 *parents;
 };
 
 enum scmi_power_scale {
···
  * @state_get: get the status of the specified clock
  * @config_oem_get: get the value of an OEM specific clock config
  * @config_oem_set: set the value of an OEM specific clock config
+ * @parent_get: get the parent id of a clk
+ * @parent_set: set the parent of a clock
  */
 struct scmi_clk_proto_ops {
 	int (*count_get)(const struct scmi_protocol_handle *ph);
···
 			      bool atomic);
 	int (*config_oem_set)(const struct scmi_protocol_handle *ph, u32 clk_id,
 			      u8 oem_type, u32 oem_val, bool atomic);
+	int (*parent_get)(const struct scmi_protocol_handle *ph, u32 clk_id, u32 *parent_id);
+	int (*parent_set)(const struct scmi_protocol_handle *ph, u32 clk_id, u32 parent_id);
 };
 
 struct scmi_perf_domain_info {