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

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Message-ID: <75496de8-51fd-4e27-9f92-babaa0e22c14@nvidia.com>
Date: Thu, 19 Jun 2025 08:17:12 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: Guenter Roeck <linux@...ck-us.net>,
 Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
 Thierry Reding <thierry.reding@...il.com>, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org, Pohsun Su <pohsuns@...dia.com>,
 Robert Lin <robelin@...dia.com>
Subject: Re: [PATCH 1/2] clocksource/drivers/timer-tegra186: Avoid 64-bit
 divide operation


On 14/06/2025 18:55, 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.
> 
> 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,


Reviewed-by: Jon Hunter <jonathanh@...dia.com>

Thanks!
Jon

-- 
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