From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Date: Thu, 05 Feb 2015 17:19:14 +0000 Subject: Re: [PATCH] clk: shmobile: div6: Avoid division by zero in .round_rate() Message-Id: <4034374.lq5RZGeRAm@avalon> List-Id: References: <1423052841-15194-1-git-send-email-geert+renesas@glider.be> <54D29760.4010009@cogentembedded.com> <54D299D6.7060809@cogentembedded.com> In-Reply-To: <54D299D6.7060809@cogentembedded.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Sergei Shtylyov Cc: Mike Turquette , Wolfram Sang , Geert Uytterhoeven , Stephen Boyd , Ulrich Hecht , Wolfram Sang , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org Hi Sergei, On Thursday 05 February 2015 01:14:46 Sergei Shtylyov wrote: > On 02/05/2015 01:04 AM, Sergei Shtylyov wrote: > >>>>> Anyone may call clk_round_rate() with a zero rate value, so we have to > >>>>> protect against that. > >>>>> > >>>>> Signed-off-by: Geert Uytterhoeven > >>>> > >>>> Acked-by: Wolfram Sang > >>>> > >>>> 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 ;-) Jokes aside, a zero frequency is the usual way to find the lowest frequency, but I agree that there aren't many integers between 0 and 1. Mike, do you have an opinion ? -- Regards, Laurent Pinchart