Re: [PATCH v4 6/8] firmware: smccc: lfa: Register DT interrupt

[Sudeep Holla <sudeep.holla@kernel.org>]

On Fri, Sep 18, 2026 at 04:11:09PM +0200, Andre Przywara wrote:
> The Arm Live Firmware Activation spec describes an asynchronous
> notification mechanism, where the platform can notify the host OS about
> newly pending image updates.
> In the absence of the ACPI notification mechanism also a simple
> devicetree node can describe an interrupt.
> 
> Add code to find the respective DT node and register the specified
> interrupt, to trigger the activation if needed.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  drivers/firmware/smccc/lfa_fw.c | 39 +++++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/firmware/smccc/lfa_fw.c b/drivers/firmware/smccc/lfa_fw.c
> index 7a55b4a6785d8..a23df331ffde9 100644
> --- a/drivers/firmware/smccc/lfa_fw.c
> +++ b/drivers/firmware/smccc/lfa_fw.c
> @@ -16,6 +16,8 @@
>  #include <linux/list.h>
>  #include <linux/module.h>
>  #include <linux/nmi.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
>  #include <linux/psci.h>
>  #include <linux/stop_machine.h>
>  #include <linux/string.h>
> @@ -871,6 +873,37 @@ static void lfa_remove_acpi(struct device *dev)
>  }
>  #endif
>  
> +static irqreturn_t lfa_irq_handler_thread(int irq, void *dev_id)
> +{
> +	int ret;
> +
> +	while (!(ret = activate_pending_image()))
> +		;

Yet again trusting firmware too much!

> +
> +	if (ret != -ENOENT)
> +		pr_warn("notified image activation failed: %d\n", ret);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int lfa_register_dt(struct device *dev)
> +{
> +	struct device_node *np;
> +	unsigned int irq;
> +
> +	np = of_find_compatible_node(NULL, NULL, "arm,lfa");
> +	if (!np)
> +		return -ENODEV;
> +
> +	irq = irq_of_parse_and_map(np, 0);
> +	of_node_put(np);
> +	if (!irq)
> +		return -ENODEV;
> +
> +	return devm_request_threaded_irq(dev, irq, NULL, lfa_irq_handler_thread,
> +					 IRQF_COND_ONESHOT, NULL, NULL);

And where can I find free_irq() ? Yes devm_() can do that for you but how
does that work with races around removal of device for example. I prefer
to have free_irq() at the very beginning of lfa_remove().

> +}
> +
>  static int lfa_smccc_probe(struct arm_smccc_device *sdev)
>  {
>  	struct arm_smccc_1_2_regs reg = { 0 };
> @@ -913,6 +946,12 @@ static int lfa_smccc_probe(struct arm_smccc_device *sdev)
>  			pr_info("registered LFA ACPI notification\n");
>  		if (err != -ENODEV)
>  			return err;
> +	} else {
> +		err = lfa_register_dt(&sdev->dev);
> +		if (!err)
> +			pr_info("registered LFA DT notification interrupt\n");
> +		if (err != -ENODEV)
> +			return err;

More code addition with absolutely no error handling 🙁.


>  	}
>  
>  	return 0;
> -- 
> 2.43.0
> 

-- 
Regards,
Sudeep