[PATCH v3 2/2] firmware: arm_scmi: Implement arm,no-completion-irq property

Marek Vasut
2026-01-15T00:49:39Z

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>
---
Cc: Conor Dooley <conor+dt@kernel.org>
Cc: Cristian Marussi <cristian.marussi@arm.com>
Cc: Florian Fainelli <florian.fainelli@broadcom.com>
Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: arm-scmi@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-renesas-soc@vger.kernel.org
---
V2: Drop no IRQ handling from SMC transport and update commit message
V3: Rename property from arm,poll-transport to arm,no-completion-irq
---
drivers/firmware/arm_scmi/common.h | 4 ++++
drivers/firmware/arm_scmi/driver.c | 4 ++++
2 files changed, 8 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 7c35c95fddbaf..7c9617d080a02 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/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;
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 3e76a3204ba4f..f167194f7cf67 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/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,
--
2.51.0