Re: [PATCH v2 2/2] firmware: arm_scmi: Implement arm,poll-transport property

[Sudeep Holla <sudeep.holla@arm.com>]

On Wed, Dec 31, 2025 at 10:29:19PM +0100, Marek Vasut wrote:
> Implement new property arm,poll-transport, 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
> ---
>  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;

My preference would be to reuse `force_polling` for this. We need to drop
const but that should be OK. Anyways I would like to know if Cristian thinks
otherwise for any reasons I might be missing to see.

-- 
Regards,
Sudeep