linux-kernel - Re: [PATCH 1/2] clocksource/drivers/timer-tegra186: Avoid 64-bit divide operation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aFq29Fr5c2TAZOYO@mai.linaro.org>
Date: Tue, 24 Jun 2025 16:32:20 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
	Pohsun Su <pohsuns@...dia.com>, Robert Lin <robelin@...dia.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 1/2] clocksource/drivers/timer-tegra186: Avoid 64-bit
 divide operation

On Sat, Jun 14, 2025 at 10:55:55AM -0700, Guenter Roeck wrote:
> Building the driver on xtensa fails with
> 
> tensa-linux-ld: drivers/clocksource/timer-tegra186.o:
> 	in function `tegra186_timer_remove':
> timer-tegra186.c:(.text+0x350):
> 	undefined reference to `__udivdi3'
> 
> Avoid the problem by rearranging the offending code to avoid the 64-bit
> divide operation.
> 

Hi Guenter,

Arnd posted a version which seems more complete.

https://lore.kernel.org/all/20250620111939.3395525-1-arnd@kernel.org/

> Fixes: 28c842c8b0f5 ("clocksource/drivers/timer-tegra186: Add WDIOC_GETTIMELEFT support")
> Cc: Pohsun Su <pohsuns@...dia.com>
> Cc: Robert Lin <robelin@...dia.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/clocksource/timer-tegra186.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-tegra186.c b/drivers/clocksource/timer-tegra186.c
> index e5394f98a02e..7b506de65438 100644
> --- a/drivers/clocksource/timer-tegra186.c
> +++ b/drivers/clocksource/timer-tegra186.c
> @@ -267,7 +267,7 @@ static unsigned int tegra186_wdt_get_timeleft(struct watchdog_device *wdd)
>  	 * counter value to the time of the counter expirations that
>  	 * remain.
>  	 */
> -	timeleft += (((u64)wdt->base.timeout * USEC_PER_SEC) / 5) * (4 - expiration);
> +	timeleft += ((u64)wdt->base.timeout * (USEC_PER_SEC / 5)) * (4 - expiration);
>  
>  	/*
>  	 * Convert the current counter value to seconds,
> -- 
> 2.45.2
> 

-- 

 <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog