Re: [PATCH v3 3/8] firmware: smccc: lfa: Add timeout and trigger watchdog

[Nirmoy Das <nirmoyd@nvidia.com>]

On Mon, 6 Jul 2026 15:44:43 +0200, Andre Przywara wrote:

Hi Andre,

> From: Vedashree Vidwans <vvidwans@nvidia.com>
>
> Enhance PRIME/ACTIVATION functions to touch watchdog and implement
> timeout mechanism. This update ensures that any potential hangs are
> detected promptly and that the LFA process is allocated sufficient
> execution time before the watchdog timer expires. These changes improve
> overall system reliability by reducing the risk of undetected process
> stalls and unexpected watchdog resets.
>
> Signed-off-by: Vedashree Vidwans <vvidwans@nvidia.com>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  drivers/firmware/smccc/lfa_fw.c | 43 ++++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/smccc/lfa_fw.c b/drivers/firmware/smccc/lfa_fw.c
> index b333b1e28c0d..357e41f95206 100644
> --- a/drivers/firmware/smccc/lfa_fw.c
> +++ b/drivers/firmware/smccc/lfa_fw.c
> @@ -6,11 +6,14 @@
>  #include <linux/arm-smccc.h>
>  #include <linux/arm-smccc-bus.h>
>  #include <linux/array_size.h>
> +#include <linux/delay.h>
>  #include <linux/fs.h>
>  #include <linux/init.h>
>  #include <linux/kobject.h>
> +#include <linux/ktime.h>
>  #include <linux/list.h>
>  #include <linux/module.h>
> +#include <linux/nmi.h>
>  #include <linux/psci.h>
>  #include <linux/stop_machine.h>
>  #include <linux/string.h>
> @@ -27,6 +30,11 @@
>  #define LFA_PRIME_CALL_AGAIN		BIT(0)
>  #define LFA_ACTIVATE_CALL_AGAIN		BIT(0)
>  
> +#define LFA_PRIME_BUDGET_MS		30000		/* 30s cap */
> +#define LFA_PRIME_DELAY_MS		10		/* 10ms between polls */
> +#define LFA_ACTIVATE_BUDGET_MS		10000		/* 10s cap */
> +#define LFA_ACTIVATE_DELAY_MS		10		/* 10ms between polls */
> +
>  /* LFA return values */
>  #define LFA_SUCCESS			0
>  #define LFA_NOT_SUPPORTED		1
> @@ -276,6 +284,7 @@ static int call_lfa_activate(void *data)
>  	struct fw_image *image = data;
>  	struct arm_smccc_1_2_regs reg = { 0 }, res;
>  
> +	touch_nmi_watchdog();
>  	reg.a0 = ARM_SMCCC_LFA_ACTIVATE;
>  	reg.a1 = image->fw_seq_id;
>  	/*
> @@ -299,6 +308,7 @@ static int call_lfa_activate(void *data)
>  
>  static int activate_fw_image(struct fw_image *image)
>  {
> +	ktime_t end = ktime_add_ms(ktime_get(), LFA_ACTIVATE_BUDGET_MS);
>  	int ret;
>  
>  retry:
> @@ -314,8 +324,14 @@ static int activate_fw_image(struct fw_image *image)
>  	}
>  
>  	/* SMC returned with call_again flag set, or with LFA_BUSY */
> -	if (ret == -LFA_CALL_AGAIN || ret == -LFA_BUSY)
> -		goto retry;
> +	if (ret == -LFA_CALL_AGAIN || ret == -LFA_BUSY) {
> +		if (ktime_before(ktime_get(), end)) {
> +			msleep_interruptible(LFA_ACTIVATE_DELAY_MS);
> +			goto retry;
> +		}
> +
> +		ret = -LFA_TIMED_OUT;
> +	}

msleep_interruptible()'s return is ignored (here and in the PRIME
loop), so a pending signal can turn this into premature retries.

>  
>  	lfa_cancel(image);
>  
> @@ -328,6 +344,7 @@ static int activate_fw_image(struct fw_image *image)
>  static int prime_fw_image(struct fw_image *image)
>  {
>  	struct arm_smccc_1_2_regs reg = { 0 }, res;
> +	ktime_t end = ktime_add_ms(ktime_get(), LFA_PRIME_BUDGET_MS);
>  
>  	if (image->may_reset_cpu) {
>  		pr_err("CPU reset not supported by kernel driver\n");
> @@ -335,6 +352,8 @@ static int prime_fw_image(struct fw_image *image)
>  		return -EINVAL;
>  	}
>  
> +	touch_nmi_watchdog();
> +
>  	reg.a0 = ARM_SMCCC_LFA_PRIME;
>  retry:
>  	/*
> @@ -353,8 +372,24 @@ static int prime_fw_image(struct fw_image *image)
>  		return res.a0;
>  	}
>  
> -	if (res.a1 & LFA_PRIME_CALL_AGAIN)
> -		goto retry;
> +	if (res.a1 & LFA_PRIME_CALL_AGAIN) {
> +		int ret;
> +
> +		/* SMC returned with call_again flag set */
> +		if (ktime_before(ktime_get(), end)) {
> +			msleep_interruptible(LFA_PRIME_DELAY_MS);
> +			goto retry;
> +		}
> +
> +		pr_err("LFA_PRIME for image %s timed out",
> +		       get_image_name(image));
> +
> +		ret = lfa_cancel(image);
> +		if (ret != 0)
> +			return ret;
> +
> +		return -ETIMEDOUT;
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.43.0

Regards,
Nirmoy