linux-kernel - Re: [PATCH 1/2] firmware: smccc: add timeout, touch wdt

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Message-ID: <cb7f90b5-6e13-4659-a448-1f621b89c71a@oss.qualcomm.com>
Date: Tue, 10 Feb 2026 15:10:21 -0800
From: Trilok Soni <trilokkumar.soni@....qualcomm.com>
To: Vedashree Vidwans <vvidwans@...dia.com>, salman.nabi@....com,
        sudeep.holla@....com, andre.przywara@....com, lpieralisi@...nel.org,
        mark.rutland@....com
Cc: ardb@...nel.org, chao.gao@...el.com, linux-arm-kernel@...ts.infradead.org,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        sdonthineni@...dia.com, vsethi@...dia.com, vwadekar@...dia.com
Subject: Re: [PATCH 1/2] firmware: smccc: add timeout, touch wdt

On 2/10/2026 2:40 PM, Vedashree Vidwans wrote:
> 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@...dia.com>
> ---
>  drivers/firmware/smccc/lfa_fw.c | 40 +++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/drivers/firmware/smccc/lfa_fw.c b/drivers/firmware/smccc/lfa_fw.c
> index da6b54fe1685..b0ace6fc8dac 100644
> --- a/drivers/firmware/smccc/lfa_fw.c
> +++ b/drivers/firmware/smccc/lfa_fw.c
> @@ -17,6 +17,9 @@
>  #include <linux/array_size.h>
>  #include <linux/list.h>
>  #include <linux/mutex.h>
> +#include <linux/nmi.h>
> +#include <linux/ktime.h>
> +#include <linux/delay.h>
>  
>  #undef pr_fmt
>  #define pr_fmt(fmt) "Arm LFA: " fmt
> @@ -37,6 +40,14 @@
>  #define LFA_PRIME_CALL_AGAIN		BIT(0)
>  #define LFA_ACTIVATE_CALL_AGAIN		BIT(0)
>  
> +/* Prime loop limits, TODO: tune after testing */

Do you want to keep this TODO? Your patches are not marked as RFC. 

> +#define LFA_PRIME_BUDGET_US		30000000	/* 30s cap */
> +#define LFA_PRIME_POLL_DELAY_US		10		/* 10us between polls */

Are these values going to be tunable from the userspace or kernel module parameters? 

> +
> +/* Activation loop limits, TODO: tune after testing */

Ditto.

> +#define LFA_ACTIVATE_BUDGET_US		20000000	/* 20s cap */
> +#define LFA_ACTIVATE_POLL_DELAY_US	10		/* 10us between polls */
...

---Trilok Soni