netdev - RE: [PATCH] enic: fix adaptive irq coalescing on 32-bit

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Date:	Fri, 23 May 2014 08:29:52 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Arnd Bergmann' <arnd@...db.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	Sujith Sankar <ssujith@...co.com>, Neel Patel <neepatel@...co.com>,
	Govindarajulu Varadarajan <_govind@....com>,
	"David S. Miller" <davem@...emloft.net>,
	Christian Benvenuti <benve@...co.com>
Subject: RE: [PATCH] enic: fix adaptive irq coalescing on 32-bit

From: Arnd Bergmann
> 7c2ce6e60f703 "enic: Add support for adaptive interrupt coalescing"
> introduced a 64-bit division that causes a link error on all 32-bit
> machines:
> 
> drivers/built-in.o: In function `enic_poll_msix':
> :(.text+0x54ff00): undefined reference to `__aeabi_uldivmod'
> 
> Since we are dividing another 32-bit value and are only interested
> in the approximate range here, it should always be safe to limit
> the delta to an u32 value.
...
>  	traffic <<= 3;
> -	traffic /= delta;
> +	traffic /= min_t(u32, delta, UINT_MAX);

I suspect that doesn't have the desired effect.
I think it is the same as:
	traffic /= (u32)delta;
If you was the correct value for large 'delta' then maybe:
	traffic = delta > UINT_MAX ? 0 : traffic / (u32)delta;

	David



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