[PATCH v8 16/17] firmware: arm_scmi: Add Raw mode coexistence support

[Cristian Marussi]

When Raw support is enabled and configured in coexistence mode the normal
SCMI drivers are allowed to register with the SCMI core and operate as
usual alongside the Raw operations.

SCMI Normal and Raw messages will be kept segregated from each other, but
only at the transaction level: any further possible interference at the
protocol layer will have instead to be handled by the user to attain
reliable results while using Raw transactions.

Signed-off-by: Cristian Marussi <cristian.marussi at arm.com>
---
v7 --> v8
- refactor to fit new scmi_debugfs_raw_mode_setup helper
v5 --> v6
- fix error path for RAW Coex on scmi_probe
---
 drivers/firmware/arm_scmi/Kconfig    | 10 ++++++++++
 drivers/firmware/arm_scmi/bus.c      |  3 ++-
 drivers/firmware/arm_scmi/driver.c   | 16 ++++++++++++----
 drivers/firmware/arm_scmi/raw_mode.c |  5 ++++-
 4 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig
index 3b4f9e92b1e3..ea0f5083ac47 100644
--- a/drivers/firmware/arm_scmi/Kconfig
+++ b/drivers/firmware/arm_scmi/Kconfig
@@ -45,6 +45,16 @@ config ARM_SCMI_RAW_MODE_SUPPORT
 	  order to avoid unexpected interactions with the SCMI Raw message
 	  flow. If unsure say N.
 
+config ARM_SCMI_RAW_MODE_SUPPORT_COEX
+	bool "Allow SCMI Raw mode coexistence with normal SCMI stack"
+	depends on ARM_SCMI_RAW_MODE_SUPPORT
+	help
+	  Allow SCMI Raw transmission mode to coexist with normal SCMI stack.
+
+	  This will allow regular SCMI drivers to register with the core and
+	  operate normally, thing which could make an SCMI test suite using the
+	  SCMI Raw mode support unreliable. If unsure, say N.
+
 config ARM_SCMI_HAVE_TRANSPORT
 	bool
 	help
diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 8601d75f5b9b..68cc4b4290c1 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -59,7 +59,8 @@ static int scmi_protocol_device_request(const struct scmi_device_id *id_table)
 	pr_debug("Requesting SCMI device (%s) for protocol %x\n",
 		 id_table->name, id_table->protocol_id);
 
-	if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT)) {
+	if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
+	    !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX)) {
 		pr_warn("SCMI Raw mode active. Rejecting '%s'/0x%02X\n",
 			id_table->name, id_table->protocol_id);
 		return -EINVAL;
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index ad4e53f0c342..282d7737cb8f 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -2616,7 +2616,6 @@ static int scmi_debugfs_raw_mode_setup(struct scmi_info *info)
 	info->raw = scmi_raw_mode_init(&info->handle, info->dbg->top_dentry,
 				       info->id, info->desc,
 				       info->tx_minfo.max_msg);
-
 	if (IS_ERR(info->raw)) {
 		dev_err(info->dev, "Failed to initialize SCMI RAW Mode !\n");
 		ret = PTR_ERR(info->raw);
@@ -2706,11 +2705,20 @@ static int scmi_probe(struct platform_device *pdev)
 			dev_warn(dev, "Failed to setup SCMI debugfs.\n");
 
 		if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT)) {
+			bool coex =
+			      IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX);
+
 			ret = scmi_debugfs_raw_mode_setup(info);
-			if (ret)
-				goto clear_dev_req_notifier;
+			if (!coex) {
+				if (ret)
+					goto clear_dev_req_notifier;
+
+				/* Bail out anyway when coex enabled */
+				return ret;
+			}
 
-			return 0;
+			/* Coex enabled, carry on in any case. */
+			dev_info(dev, "SCMI RAW Mode COEX enabled !\n");
 		}
 	}
 
diff --git a/drivers/firmware/arm_scmi/raw_mode.c b/drivers/firmware/arm_scmi/raw_mode.c
index a33ef0eaffe5..037ef9c14fae 100644
--- a/drivers/firmware/arm_scmi/raw_mode.c
+++ b/drivers/firmware/arm_scmi/raw_mode.c
@@ -26,7 +26,10 @@
  * In order to avoid possible interferences between the SCMI Raw transactions
  * originated from a test-suite and the normal operations of the SCMI drivers,
  * when Raw mode is enabled, by default, all the regular SCMI drivers are
- * inhibited.
+ * inhibited, unless CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX is enabled: in this
+ * latter case the regular SCMI stack drivers will be loaded as usual and it is
+ * up to the user of this interface to take care of manually inhibiting the
+ * regular SCMI drivers in order to avoid interferences during the test runs.
  *
  * The exposed API is as follows.
  *
-- 
2.34.1