[RFC] SCMI drivers: generic changes + Arm SMCCC transport + drafted OP-TEE transport

Documentation/devicetree/bindings/arm/arm,scmi.txt

@@ -10,21 +10,44 @@ the SCMI as described in ARM document number ARM DEN 0056A ("ARM System Control
 and Management Interface Platform Design Document")[0] provide for OSPM in
 the device tree.
 
+The SCMI agent node with its properties shall be under the /firmware/ node.
+
+Each protocol supported by an agent be defined by a sub-node in the SCMI
+agent node as described in the following sections.
+
+For a given SCMI agent node, the communication channel properties, as defined
+by related SCMI tranport compatible bindings, can be either defined in the
+root node of the SCMI device or in the subnode of the related SCMI protocol
+supported by the device. In the former case, the communcation propoerties
+are shared by all protocol. In the later case, each protocol node must
+define all communication configuration expected by the related transport
+channel.
+
+Required properties common to all SCMI agent node:
+
+- #address-cells : should be '1' if the device has sub-nodes, maps to
+	  protocol identifier for a given sub-node.
+- #size-cells : should be '0' as 'reg' property doesn't have any size
+	  associated with it.
+
+SCMI Agent over Mailbox transport channel
+-----------------------------------------
+
+SCMI messages can be exchange between agent and the SCMI server using a
+mailbox device for message notification and a piece of shared memory for
+message payload and protocol data transfer.
+
 Required properties:
 
-The scmi node with the following properties shall be under the /firmware/ node.
+- compatible : "arm,scmi"
 
-- compatible : shall be "arm,scmi"
 - mboxes: List of phandle and mailbox channel specifiers. It should contain
 	  exactly one or two mailboxes, one for transmitting messages("tx")
 	  and another optional for receiving the notifications("rx") if
 	  supported.
+
 - shmem : List of phandle pointing to the shared memory(SHM) area as per
 	  generic mailbox client binding.
-- #address-cells : should be '1' if the device has sub-nodes, maps to
-	  protocol identifier for a given sub-node.
-- #size-cells : should be '0' as 'reg' property doesn't have any size
-	  associated with it.
 
 Optional properties:
 
@@ -37,11 +60,42 @@ The mailbox is the only permitted method of calling the SCMI firmware.
 Mailbox doorbell is used as a mechanism to alert the presence of a
 messages and/or notification.
 
-Each protocol supported shall have a sub-node with corresponding compatible
-as described in the following sections. If the platform supports dedicated
-communication channel for a particular protocol, the 3 properties namely:
-mboxes, mbox-names and shmem shall be present in the sub-node corresponding
-to that protocol.
+SCMI Agent over Arm SMCCC transport channel
+-------------------------------------------
+
+On Arm based systems that support secure world invocation through secure
+monitor, SCMI messages can be exchange between agent and the SCMI server
+using an Arm SMC or HVC instruction for message notification and a piece
+of shared memory for message payload and protocol data transfer.
+
+Required properties:
+
+- compatible : "arm,scmi-smc"
+
+- shmem : List of phandle pointing to the shared memory(SHM) area as per
+	  generic mailbox client binding.
+
+- arm,smc-id : function identifier used a argument to the SMC/HVC instruction
+               as defined in Arm SMCCC specification [6].
+
+- method : "smc" or "hvc"
+            Optional property defining the conduit method for to be used
+	    for invoking the SCMI server in secure world.
+	    "smc" states instruction SMC #0 is used whereas "hvc" states
+	    instruction HVC #0 is used.
+
+SCMI Agent over on OP-TEE Service
+---------------------------------
+
+On systems that support OP-TEE, SCMI messages can be exchange between agent
+and the SCMI server using an OP-TEE invocation.
+
+Required properties:
+
+- compatible : "linaro,scmi-optee"
+
+- agent-id : agent identifier assigned to the agent/channel and known from
+	  the SCMI server in OP-TEE.
 
 Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
 ------------------------------------------------------------
@@ -104,6 +158,7 @@ Required sub-node properties:
 [3] Documentation/devicetree/bindings/thermal/thermal.txt
 [4] Documentation/devicetree/bindings/sram/sram.yaml
 [5] Documentation/devicetree/bindings/reset/reset.txt
+[6] https://developer.arm.com/docs/den0028/latest
 
 Example:
 

drivers/firmware/Kconfig

@@ -9,7 +9,7 @@ menu "Firmware Drivers"
 config ARM_SCMI_PROTOCOL
 	bool "ARM System Control and Management Interface (SCMI) Message Protocol"
 	depends on ARM || ARM64 || COMPILE_TEST
-	depends on MAILBOX
+	depends on MAILBOX || HAVE_ARM_SMCCC || OPTEE
 	help
 	  ARM System Control and Management Interface (SCMI) protocol is a
 	  set of operating system-independent software interfaces that are

drivers/firmware/arm_scmi/Makefile

@@ -2,6 +2,9 @@
 obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o scmi-transport.o
 scmi-bus-y = bus.o
 scmi-driver-y = driver.o
-scmi-transport-y = mailbox.o shmem.o
+scmi-transport-y = shmem.o
+scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
+scmi-transport-$(CONFIG_HAVE_ARM_SMCCC) += smc.o
+scmi-transport-$(CONFIG_OPTEE) += optee_service.o
 scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o
 obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o

drivers/firmware/arm_scmi/common.h

@@ -6,6 +6,8 @@
  *
  * Copyright (C) 2018 ARM Ltd.
  */
+#ifndef ARM_SCMI_COMMON_H
+#define ARM_SCMI_COMMON_H
 
 #include <linux/bitfield.h>
 #include <linux/completion.h>
@@ -172,7 +174,6 @@ struct scmi_chan_info {
 /**
  * struct scmi_transport_ops - Structure representing a SCMI transport ops
  *
- * @chan_available: Callback to check if channel is available or not
  * @chan_setup: Callback to allocate and setup a channel
  * @chan_free: Callback to free a channel
  * @send_message: Callback to send a message
@@ -181,7 +182,6 @@ struct scmi_chan_info {
  * @poll_done: Callback to poll transfer status
  */
 struct scmi_transport_ops {
-	bool (*chan_available)(struct device *dev, int idx);
 	int (*chan_setup)(struct scmi_chan_info *cinfo, struct device *dev,
 			  bool tx);
 	int (*chan_free)(int id, void *p, void *data);
@@ -210,6 +210,8 @@ struct scmi_desc {
 };
 
 extern const struct scmi_desc scmi_mailbox_desc;
+extern const struct scmi_desc scmi_smc_desc;
+extern const struct scmi_desc scmi_optee_desc;
 
 void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr);
 void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);
@@ -224,3 +226,5 @@ void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
 			  struct scmi_xfer *xfer);
 bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
 		     struct scmi_xfer *xfer);
+
+#endif /* ARM_SCMI_COMMON_H */

drivers/firmware/arm_scmi/driver.c

@@ -261,13 +261,17 @@ void scmi_xfer_put(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 
 #define SCMI_MAX_POLL_TO_NS	(100 * NSEC_PER_USEC)
 
-static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo,
-				      struct scmi_xfer *xfer, ktime_t stop)
+static bool scmi_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
 {
 	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
 
-	return info->desc->ops->poll_done(cinfo, xfer) ||
-	       ktime_after(ktime_get(), stop);
+	return info->desc->ops->poll_done(cinfo, xfer);
+}
+
+static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo,
+				      struct scmi_xfer *xfer, ktime_t stop)
+{
+	return scmi_poll_done(cinfo, xfer) || ktime_after(ktime_get(), stop);
 }
 
 /**
@@ -297,7 +301,7 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 			      xfer->hdr.poll_completion);
 
 	ret = info->desc->ops->send_message(cinfo, xfer);
-	if (ret < 0) {
+	if (ret) {
 		dev_dbg(dev, "Failed to send message %d\n", ret);
 		return ret;
 	}
@@ -307,7 +311,7 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 
 		spin_until_cond(scmi_xfer_done_no_timeout(cinfo, xfer, stop));
 
-		if (ktime_before(ktime_get(), stop))
+		if (scmi_poll_done(cinfo, xfer))
 			info->desc->ops->fetch_response(cinfo, xfer);
 		else
 			ret = -ETIMEDOUT;
@@ -566,6 +570,14 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 	return 0;
 }
 
+/* SCMI root node has no reg property */
+static bool node_is_scmi_root_node(const struct device_node *np)
+{
+	u32 protocol_id;
+
+	return of_property_read_u32(np, "reg", &protocol_id);
+}
+
 static int scmi_chan_setup(struct scmi_info *info, struct device *dev,
 			   int prot_id, bool tx)
 {
@@ -582,7 +594,8 @@ static int scmi_chan_setup(struct scmi_info *info, struct device *dev,
 	if (cinfo)
 		return 0;
 
-	if (!info->desc->ops->chan_available(dev, idx)) {
+	/* Channels are defined in SCMI device root node */
+	if (!node_is_scmi_root_node(dev->of_node)) {
 		cinfo = idr_find(idr, SCMI_PROTOCOL_BASE);
 		if (unlikely(!cinfo)) /* Possible only if platform has no Rx */
 			return -EINVAL;
@@ -826,7 +839,15 @@ ATTRIBUTE_GROUPS(versions);
 
 /* Each compatible listed below must have descriptor associated with it */
 static const struct of_device_id scmi_of_match[] = {
+#ifdef CONFIG_MAILBOX
 	{ .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
+#endif
+#ifdef CONFIG_HAVE_ARM_SMCCC
+	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
+#endif
+#ifdef CONFIG_OPTEE
+	{ .compatible = "arm,scmi-optee", .data = &scmi_optee_desc },
+#endif
 	{ /* Sentinel */ },
 };
 

drivers/firmware/arm_scmi/mailbox.c

@@ -46,12 +46,6 @@ static void rx_callback(struct mbox_client *cl, void *m)
 	scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem));
 }
 
-static bool mailbox_chan_available(struct device *dev, int idx)
-{
-	return !of_parse_phandle_with_args(dev->of_node, "mboxes",
-					   "#mbox-cells", idx, NULL);
-}
-
 static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
 			      bool tx)
 {
@@ -167,7 +161,6 @@ mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
 }
 
 static struct scmi_transport_ops scmi_mailbox_ops = {
-	.chan_available = mailbox_chan_available,
 	.chan_setup = mailbox_chan_setup,
 	.chan_free = mailbox_chan_free,
 	.send_message = mailbox_send_message,