firmware: arm_scmi: Implement arm,no-completion-irq property

Implement new property arm,no-completion-irq, which sets all SCMI
operation into poll mode. This is meant to work around uncooperative
SCP implementations, which do not generate completion interrupts.
This applies to mbox/shmem based implementations.

With this property set, such implementations which do not generate
interrupts can be interacted with, until they are fixed to generate
interrupts properly.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Message-Id: <20260117010241.186685-2-marek.vasut+renesas@mailbox.org>
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

Author: Marek Vasut

drivers/firmware/arm_scmi/common.h

@@ -235,6 +235,9 @@ struct scmi_transport_ops {
  *		      to have an execution latency lesser-equal to the threshold
  *		      should be considered for atomic mode operation: such
  *		      decision is finally left up to the SCMI drivers.
+ * @no_completion_irq: Flag to indicate that this transport has no completion
+ *		       interrupt and has to be polled. This is similar to the
+ *		       force_polling below, except this is set via DT property.
  * @force_polling: Flag to force this whole transport to use SCMI core polling
  *		   mechanism instead of completion interrupts even if available.
  * @sync_cmds_completed_on_ret: Flag to indicate that the transport assures
@@ -254,6 +257,7 @@ struct scmi_desc {
 	int max_msg;
 	int max_msg_size;
 	unsigned int atomic_threshold;
+	bool no_completion_irq;
 	const bool force_polling;
 	const bool sync_cmds_completed_on_ret;
 	const bool atomic_enabled;

drivers/firmware/arm_scmi/driver.c

@@ -2735,6 +2735,7 @@ static int scmi_chan_setup(struct scmi_info *info, struct device_node *of_node,
 	cinfo->is_p2a = !tx;
 	cinfo->rx_timeout_ms = info->desc->max_rx_timeout_ms;
 	cinfo->max_msg_size = info->desc->max_msg_size;
+	cinfo->no_completion_irq = info->desc->no_completion_irq;
 
 	/* Create a unique name for this transport device */
 	snprintf(name, 32, "__scmi_transport_device_%s_%02X",
@@ -3150,6 +3151,9 @@ static const struct scmi_desc *scmi_transport_setup(struct device *dev)
 	if (ret && ret != -EINVAL)
 		dev_err(dev, "Malformed arm,max-msg DT property.\n");
 
+	trans->desc.no_completion_irq = of_property_read_bool(dev->of_node,
+							      "arm,no-completion-irq");
+
 	dev_info(dev,
 		 "SCMI max-rx-timeout: %dms / max-msg-size: %dbytes / max-msg: %d\n",
 		 trans->desc.max_rx_timeout_ms, trans->desc.max_msg_size,