soc: qcom: rpmh: Add support to read back resource settings

All rpmh_*() APIs so far have supported placing votes for various resource
settings but the H/W also have option to read resource settings.

Add new rpmh_read() API to allow clients to read back resource setting
from H/W. This will be useful for clients like regulators, which currently
don't have a way to know the settings applied during bootloader stage.

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Maulik Shah <maulik.shah@oss.qualcomm.com>
Signed-off-by: Kamal Wadhwa <kamal.wadhwa@oss.qualcomm.com>
Link: https://patch.msgid.link/20260801-b4-read-rpmh-v5-v6-1-9fcb54928523@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/soc/qcom/rpmh-rsc.c

@@ -443,6 +443,7 @@ static irqreturn_t tcs_tx_done(int irq, void *p)
 	int i;
 	unsigned long irq_status;
 	const struct tcs_request *req;
+	u32 reg;
 
 	irq_status = readl_relaxed(drv->tcs_base + drv->regs[RSC_DRV_IRQ_STATUS]);
 
@@ -453,6 +454,11 @@ static irqreturn_t tcs_tx_done(int irq, void *p)
 
 		trace_rpmh_tx_done(drv, i, req);
 
+		if (req->is_read) {
+			reg = drv->regs[RSC_DRV_CMD_RESP_DATA];
+			req->cmds[0].data = read_tcs_reg(drv, reg, i);
+		}
+
 		/* Clear AMC trigger & enable modes and
 		 * disable interrupt for this TCS
 		 */
@@ -493,13 +499,15 @@ 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;
 	struct tcs_cmd *cmd;
 	int i, j;
 
 	/* Convert all commands to RR when the request has wait_for_compl set */
 	cmd_msgid |= msg->wait_for_compl ? CMD_MSGID_RESP_REQ : 0;
+	if (!msg->is_read)
+		cmd_msgid |= CMD_MSGID_WRITE;
 
 	for (i = 0, j = cmd_id; i < msg->num_cmds; i++, j++) {
 		cmd = &msg->cmds[i];
@@ -513,7 +521,8 @@ 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);
 		trace_rpmh_send_msg(drv, tcs_id, msg->state, j, msgid, cmd);
 	}
 

drivers/soc/qcom/rpmh.c

@@ -175,6 +175,9 @@ static int __rpmh_write(const struct device *dev, enum rpmh_state state,
 	struct cache_req *req;
 	int i;
 
+	if (rpm_msg->msg.is_read)
+		goto send_data;
+
 	/* Cache the request in our store and link the payload */
 	for (i = 0; i < rpm_msg->msg.num_cmds; i++) {
 		req = cache_rpm_request(ctrlr, state, &rpm_msg->msg.cmds[i]);
@@ -182,6 +185,7 @@ static int __rpmh_write(const struct device *dev, enum rpmh_state state,
 			return PTR_ERR(req);
 	}
 
+send_data:
 	if (state == RPMH_ACTIVE_ONLY_STATE) {
 		ret = rpmh_rsc_send_data(ctrlr_to_drv(ctrlr), &rpm_msg->msg);
 	} else {
@@ -194,7 +198,7 @@ static int __rpmh_write(const struct device *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;
@@ -204,10 +208,45 @@ 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;
 
 	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.
+ *
+ * Context: May sleep. Do not call from atomic contexts.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+int rpmh_read(const struct device *dev, struct tcs_cmd *cmd)
+{
+	DECLARE_COMPLETION_ONSTACK(compl);
+	DEFINE_RPMH_MSG_ONSTACK(dev, RPMH_ACTIVE_ONLY_STATE, &compl, rpm_msg);
+	int ret;
+
+	ret = __fill_rpmh_msg(&rpm_msg, RPMH_ACTIVE_ONLY_STATE, cmd, 1, true);
+	if (ret)
+		return ret;
+
+	ret = __rpmh_write(dev, RPMH_ACTIVE_ONLY_STATE, &rpm_msg);
+	if (ret)
+		return ret;
+
+	ret = wait_for_completion_timeout(&compl, RPMH_TIMEOUT_MS);
+	cmd[0].data = rpm_msg.cmd[0].data;
+
+	return (ret > 0) ? 0 : -ETIMEDOUT;
+}
+EXPORT_SYMBOL_GPL(rpmh_read);
+
 /**
  * rpmh_write_async: Write a set of RPMH commands
  *
@@ -230,7 +269,7 @@ int rpmh_write_async(const struct device *dev, enum rpmh_state state,
 		return -ENOMEM;
 	rpm_msg->needs_free = true;
 
-	ret = __fill_rpmh_msg(rpm_msg, state, cmd, n);
+	ret = __fill_rpmh_msg(rpm_msg, state, cmd, n, false);
 	if (ret) {
 		kfree(rpm_msg);
 		return ret;
@@ -257,7 +296,7 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
 	DEFINE_RPMH_MSG_ONSTACK(dev, state, &compl, 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;
 
@@ -352,7 +391,7 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
 	rpm_msgs = req->rpm_msgs;
 
 	for (i = 0; i < count; i++) {
-		__fill_rpmh_msg(rpm_msgs + i, state, cmd, n[i]);
+		__fill_rpmh_msg(rpm_msgs + i, state, cmd, n[i], false);
 		cmd += n[i];
 	}
 

include/soc/qcom/rpmh.h

@@ -11,6 +11,8 @@
 
 
 #if IS_ENABLED(CONFIG_QCOM_RPMH)
+int rpmh_read(const struct device *dev, struct tcs_cmd *cmd);
+
 int rpmh_write(const struct device *dev, enum rpmh_state state,
 	       const struct tcs_cmd *cmd, u32 n);
 
@@ -24,6 +26,9 @@ void rpmh_invalidate(const struct device *dev);
 
 #else
 
+static inline int rpmh_read(const struct device *dev, struct tcs_cmd *cmd)
+{ return -ENODEV; }
+
 static inline int rpmh_write(const struct device *dev, enum rpmh_state state,
 			     const struct tcs_cmd *cmd, u32 n)
 { return -ENODEV; }

include/soc/qcom/tcs.h

@@ -51,6 +51,7 @@ struct tcs_cmd {
  * struct tcs_request: A set of tcs_cmds sent together in a TCS
  *
  * @state:          state for the request.
+ * @is_read:        set for read only requests
  * @wait_for_compl: wait until we get a response from the h/w accelerator
  *                  (same as setting cmd->wait for all commands in the request)
  * @num_cmds:       the number of @cmds in this request
@@ -58,6 +59,7 @@ struct tcs_cmd {
  */
 struct tcs_request {
 	enum rpmh_state state;
+	bool is_read;
 	u32 wait_for_compl;
 	u32 num_cmds;
 	struct tcs_cmd *cmds;