From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Holt Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source. Date: Tue, 9 Aug 2011 07:49:19 -0500 Message-ID: <20110809124919.GS4926@sgi.com> References: <20110808144424.GY4926@sgi.com> <4E3FF9EA.6030601@grandegger.com> <4E3FFD5B.7080000@pengutronix.de> <4E4001E1.3030508@grandegger.com> <4E403097.4020306@pengutronix.de> <9C64B7751C3BCA41B64A68E23005A7BE1B9D6C@039-SN1MPN1-002.039d.mgd.msft.net> <4E40F09F.60305@grandegger.com> <9C64B7751C3BCA41B64A68E23005A7BE1BDF8C@039-SN1MPN1-004.039d.mgd.msft.net> <4E41108F.1090104@grandegger.com> <9C64B7751C3BCA41B64A68E23005A7BE1C3552@039-SN1MPN1-002.039d.mgd.msft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: "socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org" , "netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "Devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , Marc Kleine-Budde , Wolfgang Grandegger To: U Bhaskar-B22300 Return-path: Content-Disposition: inline In-Reply-To: <9C64B7751C3BCA41B64A68E23005A7BE1C3552-TcFNo7jSaXPiTqIcKZ1S2K4g8xLGJsHaLnY5E4hWTkheoWH0uzbU5w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: socketcan-core-bounces-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org Errors-To: socketcan-core-bounces-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org List-Id: netdev.vger.kernel.org On Tue, Aug 09, 2011 at 12:41:39PM +0000, U Bhaskar-B22300 wrote: > > > > -----Original Message----- > > From: Wolfgang Grandegger [mailto:wg-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org] > > Sent: Tuesday, August 09, 2011 4:19 PM > > To: U Bhaskar-B22300 > > Cc: Marc Kleine-Budde; socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org; > > netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > > Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source. > > > > On 08/09/2011 11:27 AM, U Bhaskar-B22300 wrote: > > > > > > > > >> -----Original Message----- > > >> From: Wolfgang Grandegger [mailto:wg-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org] > > >> Sent: Tuesday, August 09, 2011 2:03 PM > > >> To: U Bhaskar-B22300 > > >> Cc: Marc Kleine-Budde; socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org; > > >> netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; Devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org > > >> Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source. > > >> > > >> Hi Bhaskar, > > >> > > >> On 08/09/2011 09:57 AM, U Bhaskar-B22300 wrote: > > >>> > > >>> > > >>>> -----Original Message----- > > >>>> From: Marc Kleine-Budde [mailto:mkl-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org] > > >>>> Sent: Tuesday, August 09, 2011 12:23 AM > > >>>> To: Wolfgang Grandegger > > >>>> Cc: socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org; netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; U > > >>>> Bhaskar- B22300 > > >>>> Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source. > > >>>> > > >>>> On 08/08/2011 05:33 PM, Wolfgang Grandegger wrote: > > >>>>>> ACK - The device tree bindings as in mainline's Documentation is > > >>>>>> a > > >>>> mess. > > >>>>>> If the powerpc guys are happy with a clock interfaces based > > >>>>>> approach somewhere in arch/ppc, I'm more than happy to remove: > > >>>>>> - fsl,flexcan-clock-source (not implemented, even in the fsl > > >>>>>> driver) > > >>> [Bhaskar]I have pushed the FlexCAN series of patches, It contains > > >>> the usage of all the fields posted in the FlexCAN bindings at > > >>> http://git.kernel.org/?p=linux/kernel/git/stable/linux-3.0.y.git;a=b > > >>> lo > > >>> b;f=Documentation/devicetree/bindings/net/can/fsl-flexcan.txt;h=1a72 > > >>> 9f > > >>> 089866259ef82d0db5893ff7a8c54d5ccf;hb=94ed5b4788a7cdbe68bc7cb8516972 > > >>> cb > > >>> ebdc8274 > > >> > > >> As Marc already pointed out, Robin already has a much more advanced > > >> patch stack in preparation. Especially your patches do not care about > > >> the already existing Flexcan core on the Freescale's ARM socks. > > > [Bhaskar] No, the patches are taking care of the existing ARM > > functionality. > > > I have not tested on the ARM based board, but the patches are made > > in a > > > Manner that it should not break the ARM based functionality. > > >> > > >>>>>> > > >>>>>> - fsl,flexcan-clock-divider \__ replace with code in arch/ppc, or > > >>>>>> - clock-frequency / a single clock-frequency attribute > > >>>>> > > >>>>> In the "net-next-2.6" tree there is also: > > >>>>> > > >>>>> $ grep flexcan arch/powerpc/boots/dts/*.dts > > >>>>> p1010rdb.dts: fsl,flexcan-clock-source = > > >> "platform"; > > >>>>> p1010rdb.dts: fsl,flexcan-clock-source = > > >> "platform"; > > >>>>> p1010si.dtsi: compatible = "fsl,flexcan-v1.0"; > > >>>>> p1010si.dtsi: fsl,flexcan-clock-divider = <2>; > > >>>>> p1010si.dtsi: compatible = "fsl,flexcan-v1.0"; > > >>>>> p1010si.dtsi: fsl,flexcan-clock-divider = <2>; > > >>>>> > > >>>>> Especially the fsl,flexcan-clock-divider = <2>; might make people > > >>>>> think, that they could set something else. > > >>>> > > >>> [Bhaskar] As it is mentioned in the Flexcan bindings, the need of > > >> fsl,flexcan-clock-divider = <2>; > > >>> But I kept it as "2" because FlexCan clock source is the > > >> platform clock and it is CCB/2 > > >>> If the "2" is misleading, the bindings can be changed or some > > >> text can be written to make the meaning of "2" > > >>> Understandable , Please suggest .. > > >> > > >> The clock source and frequency is fixed. Why do we need an extra > > >> properties for that. We have panned to remove these bogus bindings > > >> from the Linux kernel, which sneaked in *without* any review on the > > >> relevant mailing lists (at least I have not realized any posting). We > > >> do not think they are really needed. They just confuse the user. We > > >> also prefer to use the compatibility string "fsl,flexcan" instead > > >> "fsl,flexcan-v1.0". It's unusual to add a version number, which is > > >> for the Flexcan on the PowerPC cores only, I assume, but there will > > >> be device tree for ARM soon. A proper compatibility string would be > > >> "fsl,p1010-flexcan" if we really need to distinguish. > > >> > > > [Bhaskar] About clock source.. There can be two sources of clock for > > the CAN. > > > Oscillator or the platform clock, but at present only platform > > clock is supported > > > in P1010.If we remove the fsl,flexcan-clock-source property, we > > will lost the flexibility > > > of changing the clock source .. > > > > > > About clock-frequency... it is also not fixed. It depends on > > the platform clock which in turns > > > Depends on the CCB clock. So it will be better to keep clock- > > frequency property which is getting fixed via u-boot. > > > > The frequency is fixed to CCB-frequency / 2. Will that ever change? What > > can we expect from future Flexcan hardware? Will it support further clock > > sources? > [Bhaskar] Yes the frequency will always be CCB-frequency/2.Even if the CCB gets changed that will be taken care by the u-boot fixup code for > clock-frequency. clock-frequency is not filled by somebody in the dts file. It will be done by u-boot. > For clock source,I can't say right now, that's why I have kept a property for this in the can node. So that in future, we need to fill it > appropriately Speaking of the dts file, I have left the p1010si.dtsi file with the fsl,flexcan-v1.0 .compatible definition. The flexcan folks (IIRC Wolfgang) objected to that as it does not follow the standard which should be just fsl,flexcan. How would you like to change that? Should I add it as part of this patch, add another patch to the series, or let you take care of it? Also, I assume the uboot project will need to be changed as well to reflect the corrected name. Thanks, Robin