> -----Original Message----- > From: Wolfgang Grandegger [mailto:w...@grandegger.com] > Sent: Tuesday, August 09, 2011 4:19 PM > To: U Bhaskar-B22300 > Cc: Marc Kleine-Budde; socketcan-core@lists.berlios.de; > net...@vger.kernel.org; devicetree-disc...@lists.ozlabs.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:w...@grandegger.com] > >> Sent: Tuesday, August 09, 2011 2:03 PM > >> To: U Bhaskar-B22300 > >> Cc: Marc Kleine-Budde; socketcan-core@lists.berlios.de; > >> net...@vger.kernel.org; devicetree-disc...@lists.ozlabs.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:m...@pengutronix.de] > >>>> Sent: Tuesday, August 09, 2011 12:23 AM > >>>> To: Wolfgang Grandegger > >>>> Cc: socketcan-core@lists.berlios.de; net...@vger.kernel.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 > > Wolfgang.
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