netdev - Re: [PATCH 1/2] can: rcar_can: Add r8a7795 support

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Date:	Mon, 29 Feb 2016 11:00:09 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Ramesh Shanmugasundaram <ramesh.shanmugasundaram@...renesas.com>,
	"wg@...ndegger.com" <wg@...ndegger.com>,
	"horms@...ge.net.au" <horms@...ge.net.au>,
	"magnus.damm@...il.com" <magnus.damm@...il.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>
Cc:	"linux-renesas-soc@...r.kernel.org" 
	<linux-renesas-soc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Chris Paterson <Chris.Paterson2@...esas.com>
Subject: Re: [PATCH 1/2] can: rcar_can: Add r8a7795 support

On 02/29/2016 10:56 AM, Ramesh Shanmugasundaram wrote:
>> On 02/29/2016 10:21 AM, Ramesh Shanmugasundaram wrote:
>>> Added r8a7795 SoC support.
>>>
>>> For smoother bit timing calculation, the rounded clock frequency is
>> used.
>>
>> Why this? From my point of view this introduces a clock error.
> 
> Thanks for the comments. 
> 
> Without the rounded clock, can_calc_bittiming returns different BRP
> values and reports high sampling error percentage. However, the
> rounded clock shows no such issues and it works fine for all
> bitrates.
> 
> Below is an e.g. from my board for an input clock differs by 2Hz.

I think it's better to fix the algorithm. I'll look into it.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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