Re: [PATCH v4 2/2] firmware: arm_scmi: Implement arm,no-completion-irq property

[Cristian Marussi <cristian.marussi@arm.com>]

On Sat, Jan 17, 2026 at 02:02:29AM +0100, Marek Vasut wrote:
> 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
> V4: No change
> ---
>  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,

LGTM.

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>

Thanks,
Cristian