soc/qcom: rpmh: add RPMh read

Implement support for RPMh reads, these allow reading out the
current votes for RPMh controlled resources such as regulators and
interconnects.

Link: https://patch.msgid.link/20260108-rpmh-regulator-fixes-v1-4-d1b5b300b665@linaro.org
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>

drivers/soc/qcom/rpmh-rsc.c

@@ -282,12 +282,15 @@ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
 			       const struct tcs_request *msg)
 {
 	u32 msgid;
-	u32 cmd_msgid = CMD_MSGID_LEN | CMD_MSGID_WRITE;
+	u32 cmd_msgid = CMD_MSGID_LEN;
 	u32 cmd_enable = 0;
 	u32 cmd_complete = 0;
 	struct tcs_cmd *cmd;
 	int i, j;
 
+	if (!msg->is_read)
+		cmd_msgid |= CMD_MSGID_WRITE;
+
 	if (msg->wait_for_compl)
 		cmd_msgid |= CMD_MSGID_RESP_REQ;
 
@@ -302,7 +305,8 @@ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
 
 		write_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_MSGID], tcs_id, j, msgid);
 		write_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_ADDR], tcs_id, j, cmd->addr);
-		write_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_DATA], tcs_id, j, cmd->data);
+		if (!msg->is_read)
+			write_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_DATA], tcs_id, j, cmd->data);
 		debug("tcs(%d): [%s] cmd_id: %d: msgid: %#x addr: %#x data: %#x complete: %#x\n",
 		      tcs_id, msg->state == RPMH_ACTIVE_ONLY_STATE ? "active" : "?", j, msgid,
 		      cmd->addr, cmd->data, cmd_complete);
@@ -418,6 +422,12 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
 		udelay(1);
 	}
 
+	/* U-Boot: read the response now we know it's available */
+	if (msg->is_read) {
+		msg->cmds[0].data = read_tcs_cmd(drv, drv->regs[RSC_DRV_CMD_RESP_DATA], tcs_id, 0);
+		log_debug("data response: %#x\n", msg->cmds[0].data);
+	}
+
 	__tcs_set_trigger(drv, tcs_id, false);
 
 	/* Reclaim the TCS */

drivers/soc/qcom/rpmh.c

@@ -68,7 +68,7 @@ static int __rpmh_write(const struct udevice *dev, enum rpmh_state state,
 }
 
 static int __fill_rpmh_msg(struct rpmh_request *req, enum rpmh_state state,
-			   const struct tcs_cmd *cmd, u32 n)
+			   const struct tcs_cmd *cmd, u32 n, bool is_read)
 {
 	if (!cmd || !n || n > MAX_RPMH_PAYLOAD)
 		return -EINVAL;
@@ -78,12 +78,45 @@ static int __fill_rpmh_msg(struct rpmh_request *req, enum rpmh_state state,
 	req->msg.state = state;
 	req->msg.cmds = req->cmd;
 	req->msg.num_cmds = n;
+	req->msg.is_read = is_read;
 
 	debug("rpmh_msg: %d, %d cmds [first %#x/%#x]\n", state, n, cmd->addr, cmd->data);
 
 	return 0;
 }
 
+/**
+ * rpmh_read: Read a resource value
+ *
+ * @dev: The device making the request
+ * @cmd: The payload having address of resource to read
+ *
+ * Reads the value for the resource address given in tcs_cmd->addr
+ * and returns the tcs_cmd->data filled with same.
+ *
+ * May sleep. Do not call from atomic contexts.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+int rpmh_read(const struct udevice *dev, enum rpmh_state state, struct tcs_cmd *cmd)
+{
+	DEFINE_RPMH_MSG_ONSTACK(dev, state, rpm_msg);
+	int ret;
+
+	ret = __fill_rpmh_msg(&rpm_msg, state, cmd, 1, true);
+	if (ret)
+		return ret;
+
+	ret = __rpmh_write(dev, state, &rpm_msg);
+	if (ret)
+		return ret;
+
+	/* Read back the response into the cmd data structure */
+	cmd->data = rpm_msg.cmd[0].data;
+
+	return (ret > 0) ? 0 : ret;
+}
+
 /**
  * rpmh_write: Write a set of RPMH commands and block until response
  *
@@ -100,7 +133,7 @@ int rpmh_write(const struct udevice *dev, enum rpmh_state state,
 	DEFINE_RPMH_MSG_ONSTACK(dev, state, rpm_msg);
 	int ret;
 
-	ret = __fill_rpmh_msg(&rpm_msg, state, cmd, n);
+	ret = __fill_rpmh_msg(&rpm_msg, state, cmd, n, false);
 	if (ret)
 		return ret;
 

include/soc/qcom/rpmh.h

@@ -13,12 +13,14 @@
 #if IS_ENABLED(CONFIG_QCOM_RPMH)
 int rpmh_write(const struct udevice *dev, enum rpmh_state state,
 	       const struct tcs_cmd *cmd, u32 n);
-
+int rpmh_read(const struct udevice *dev, enum rpmh_state state, struct tcs_cmd *cmd);
 #else
 
 static inline int rpmh_write(const struct device *dev, enum rpmh_state state,
 			     const struct tcs_cmd *cmd, u32 n)
 { return -ENODEV; }
+static inline int rpmh_read(const struct udevice *dev, struct tcs_cmd *cmd)
+{ return -ENODEV; }
 
 #endif /* CONFIG_QCOM_RPMH */
 

include/soc/qcom/tcs.h

@@ -55,6 +55,7 @@ struct tcs_cmd {
  */
 struct tcs_request {
 	enum rpmh_state state;
+	bool is_read;
 	u32 wait_for_compl;
 	u32 num_cmds;
 	struct tcs_cmd *cmds;