On Thu, Jul 03, 2014 at 11:20:27AM +0200, Marc Kleine-Budde wrote:
> On 07/03/2014 11:09 AM, Dong Aisheng wrote:
> > On Thu, Jul 03, 2014 at 11:04:36AM +0200, Marc Kleine-Budde wrote:
> >> On 07/03/2014 10:48 AM, Dong Aisheng wrote:
> >>> On Thu, Jul 03, 2014 at 09:12:49AM +0200, Marc Kleine-Budde wrote:
> >>>> On 07/03/2014 05:48 AM, Dong Aisheng wrote:
> >>>>> On Wed, Jul 02, 2014 at 09:13:07PM +0200, Marc Kleine-Budde wrote:
> >>>>>> On 07/02/2014 07:54 PM, Oliver Hartkopp wrote:
> >>>>>>> I'm not really familiar with the naming concept in device trees.
> >>>>>>>
> >>>>>>> What is your opinion about the remarks below?
> >>>>>>
> >>>>>> The entries in the DT, at least on freescale baords, follow the naming
> >>>>>> scheme of the reference manual. E.g. on the mx25 it's can1 and can2:
> >>>>>>
> >>>>>> can1: can@43f88000 { ... }
> >>>>>> can2: can@43f8c000 { ... }
> >>>>>>
> >>>>>> And on the mx28, its:
> >>>>>>
> >>>>>> can0: can@80032000 { ... }
> >>>>>> can1: can@80034000 { ... }
> >>>>>>
> >>>>>> Because the imx25 datasheet uses a "1" based counting scheme, while the
> >>>>>> imx28 uses a "0" based one.
> >>>>>>
> >>>>>> So it's best practise to follow the naming and numbering scheme of the
> >>>>>> hardware reference manual.....and if you have access to the
> >>>>>> documentation of the m_can core, use clock names of the m_can core for
> >>>>>> the clock-names property.
> >>>>>>
> >>>>>
> >>>>> Based on my knowledge, device tree allows define phandle name according to
> >>>>> the real device name of HW according spec while the device node name should
> >>>>> be general(e.g can@80032000 rather than flexcan@80032000).
> >>>>> For imx6sx, there are already following entries in
> >>>>> arch/arm/boot/dts/imx6sx.dtsi
> >>>>> flexcan1: can@02090000 {...}
> >>>>> flexcan2: can@02094000 {...}
> >>>>> So i'd prefer to define as:
> >>>>> m_can1: canfd@020e8000 {...}
> >>>>> m_can2: canfd@020f0000 {...}
> >>>>>
> >>>>>
> >>>>> One problem is there're can alias already.
> >>>>> aliases {
> >>>>> can0 = &flexcan1;
> >>>>> can1 = &flexcan2;
> >>>>> ...
> >>>>> }
> >>>>> I'm not sure adding can2&can3 for mcan is properly:
> >>>>> aliases {
> >>>>> can0 = &flexcan1;
> >>>>> can1 = &flexcan2;
> >>>>> can2 = &m_can1;
> >>>>> can3 = &m_can2;
> >>>>> ...
> >>>>> }
> >>>>> Since the m_can driver does not need to use aliases,
> >>>>> so i will not add them.
> >>>>
> >>>> IMHO It's fine too add the can{2,3} aliases to m_can, too.
> >>>>
> >>>
> >>> I think the main problem for doing this way is that the meaning of id
> >>> return by of_alias_get_id may be not persistent.
> >>> e.g
> >>> For MX6SX
> >>> aliases {
> >>> can0 = &flexcan1;
> >>> can1 = &flexcan2;
> >>> can2 = &m_can1;
> >>> can3 = &m_can2;
> >>> ...
> >>> }
> >>>
> >>> For other platform, it could be:
> >>> aliases {
> >>> can0 = &m_can1;
> >>> can1 = &m_can2;
> >>> ...
> >>> }
> >>> It's hard for driver to use.
> >>
> >> The driver doesn't make use of it, does it?
> >>
> >>> And actually the M_CAN driver does not need to use the alias.
> >>> So i wonder if it makes sense to add the alias for m_can devices
> >>> like that.
> >>
> >> For example the imx53 has two different SPI units, in the alias section
> >> we see:
> >>
> >> spi0 = &ecspi1;
> >> spi1 = &ecspi2;
> >> spi2 = &cspi;
> >
> > Thanks for the info.
> > I'm not clear what's our purpose adding alias like this?
> > Can you help explain it a bit?
>
> You can use the alias in your dts to refer to the node instead of the
> more complicate name.
> Further you bring a order to all devices of the
> same type and you can make use of the number in the alias for other
> purposes, which is however not used for CAN afaik.
>
> > Do we need adding alias for all exist devices?
>
> Have a look at the existing imx*.dtsi files. If there are already
> aliases for a given device type, then it makes sense to add new devices
> of that type to the alias aswell.
>
Okay, clear now, thanks for the information.
Regards
Dong Aisheng
> 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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