linux-kernel - Re: [PATCH v2] drm/pl111: Use 64-bit arithmetic instead of 32-bit

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Date:   Tue, 17 Jul 2018 11:40:07 -0700
From:   Eric Anholt <eric@...olt.net>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: Re: [PATCH v2] drm/pl111: Use 64-bit arithmetic instead of 32-bit

"Gustavo A. R. Silva" <gustavo@...eddedor.com> writes:

> Add suffix ULL to constant 1000 in order to give the compiler complete
> information about the proper arithmetic to use.
>
> Notice that such constant is used in a context that expects an
> expression of type u64 (64 bits, unsigned) and the following
> expression is currently being evaluated using 32-bit arithmetic:
>
> mode->clock * 1000
>
> Addresses-Coverity-ID: 1466139 ("Unintentional integer overflow")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

This is silly.  The clock won't be over 4ghz -- we haven't seen anything
over 1024x768 on this hardware as far as I know.  The u64 is for the
multiplication by width/height below.

I've still applied the patch to shut up the tool.

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