linux-kernel - [problem on 32-bit systems] changing the type of clk

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Message-ID: <CAK7LNAQL=G7hkVDgcGCM60Lq4Omx25-qb=TkXUKOO2CzeargTg@mail.gmail.com>
Date:   Sat, 15 Oct 2016 11:55:38 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     linux-clk <linux-clk@...r.kernel.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [problem on 32-bit systems] changing the type of clk_rate to "long long"?

Hi.

When I was testing my clk driver + generic cpufreq driver,
I was hit by a problem.

Everything worked fine on my 64-bit SoCs,
but not on 32-bit SoCs.

I found the cause of the problem was
that the type of clk_rate is "long".

It is long enough on 64-bit systems,
but only 32-bit wide on 32-bit systems.

The CPU clocks on my SoCs
are derived from a 2.4GHz PLL.

The .round_rate() callback tries to return 2400000000,
but it does not fit in a signed 32-bit-wide variable
and it is treated as -1894967296, which is an error.

In order to handle clock frequency safely,
shall we use "long long" instead?
(It is guaranteed to have 64-bit width)

-- 
Best Regards
Masahiro Yamada