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

[Andre Przywara]

Hi,

On 7/10/26 12:08, Nirmoy Das wrote:
> On Mon, 6 Jul 2026 15:44:43 +0200, Andre Przywara wrote:
>
> Hi Andre,
>
> > From: Vedashree Vidwans <vvidwans@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > ---
> >   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.

Ah, thanks, that's a good point. I fixed that now. I don't think it 
really matters for the 10ms delay here, but it would break the outer 
timeout as well, which is a couple of seconds.

Cheers,
Andre

> >   
> >   	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