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From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Mike Turquette <mturquette@linaro.org>,
	Wolfram Sang <wsa@the-dreams.de>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Ulrich Hecht <ulrich.hecht+renesas@gmail.com>,
	Wolfram Sang <wsa@sang-engineering.com>,
	linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] clk: shmobile: div6: Avoid division by zero in .round_rate()
Date: Fri, 06 Feb 2015 14:12:13 +0300	[thread overview]
Message-ID: <54D4A18D.3010504@cogentembedded.com> (raw)
In-Reply-To: <4034374.lq5RZGeRAm@avalon>

Hello.

On 2/5/2015 8:19 PM, Laurent Pinchart wrote:

>>>>>>> Anyone may call clk_round_rate() with a zero rate value, so we have to
>>>>>>> protect against that.

>>>>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

>>>>>> Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

>>>>>> I agree that this should not be fixed in the core because the fixup is
>>>>>> really driver dependant.

>>>>> Dunno, zero frequency seems generally insane to me.

>>>> It is useful to find the lowest frequency a clock can support. Basically
>>>> it is a search for the floor frequency.

>>> Why not just use 1? Or are you assuming that some hardware could actually
>>> support 0 Hz?

>> Replying to myself: yes, this has happened to me, when I forgot to override
>> the EXTAL frequency in the board .dts file (default was 0).

> So it was a good thing that the driver crashed, it let you find a bug ;-)

    None of the clock drivers crashed, but the SDHI driver hanged instead, and 
I spent much time tracing it in order to find where it hanged. :-/

WBR, Sergei


  parent reply	other threads:[~2015-02-06 11:12 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-04 12:27 Geert Uytterhoeven
2015-02-04 13:31 ` Sergei Shtylyov
2015-02-04 13:50   ` Laurent Pinchart
2015-02-04 17:32 ` Wolfram Sang
2015-02-04 17:45   ` Sergei Shtylyov
2015-02-04 22:01     ` Mike Turquette
2015-02-04 22:04       ` Sergei Shtylyov
2015-02-04 22:14         ` Sergei Shtylyov
2015-02-05 17:19           ` Laurent Pinchart
2015-02-05 17:46             ` Mike Turquette
2015-02-06 11:12             ` Sergei Shtylyov [this message]
2015-02-04 22:05   ` Mike Turquette

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