Hi Stephen, On 05/29/2013 05:27 PM, Stephen Warren wrote: > On 05/29/2013 02:39 AM, Benoit Cousson wrote: >> Hi Afzal, >> >> On 05/29/2013 10:06 AM, Mohammed, Afzal wrote: >>> Hi Jon, >>> >>> On Wed, May 29, 2013 at 03:35:10, Stephen Warren wrote: >>>> On 05/28/2013 03:25 PM, Jon Hunter wrote: >>> >>>>>> ti,am335x-timer (applicable to AM335x devices) >>>>>> ti,am335x-timer-1ms (applicable to AM335x devices) >>>>>> + "ti,am4372-timer-1ms", "ti,am335x-timer-1ms" for AM43x 1ms timer >>>>>> + "ti,am4372-timer", "ti,am335x-timer" for AM43x timers other than 1ms one >>> >>>>> If you are adding more compatibility strings, then this implies that the >>>>> AM43x timers are not 100% compatible with any other device listed (such >>>>> as am335x or any omap device). That's fine but you should state that in >>>>> the changelog. If the AM43x timer registers are 100% compatible with >>>>> existing devices you should not add these. >>>> >>>> I'm not sure that's true; .dts files should always include a compatible >>>> value that describes the most specific model of the HW, plus any >>>> baseline compatible value that the HW is compatible with. This allows >>>> any required quirks/fixes/... to be applied for the specific HW model >>>> later even if nobody knows right now they'll be needed. Hence, defining >>>> new compatible values doesn't necessarily mean incompatible HW. >>> >>> Stephen took words out of my finger ;) >>> >>> Some explanations,I don;t >>> >>> 1. first compatible should be exact device [A], followed by compatible >>> model (if one) >>> 2. Minor effort in getting DT right the first time may help prevent >>> difficult effort later modifying it (if a necessity comes), considering >>> the fact that DT sources has to move out of Kernel at some point of >>> time. And DT is not supposed to be modified, which may cause difficulty >>> for the users (I had been a minor victim of this during rebase). >>> >>> As we both were in GPMC land earlier, an example, >>> >>> If my memory is right, GPMC IP in am335x is rev 6, and IP has 8 chip >>> select, but one is not pinned out. Now assume that same IP is integrated >>> in another SoC (probably OMAP4 has rev 6). Here if we use same compatible >>> for both, driver cannot handle it properly (w/o knowledge about platform). >>> But if exact compatible is mentioned, without modifying DT (which should >>> be considered as a firmware) just by modifying Kernel, deciding based on >>> compatible would help achieve what is required. >> >> That's true for the DTS itself, but here your are changing the binding >> documentation which is supposed to reflect the driver "interface" in the >> Device Tree model description. >> >> Since the driver does not support any new compatible string, you should >> not update the binding. > > I don't agree here; the DT binding should define all the required and/or > allowed values that must/should/can be present in the DT - the entire > legal schema. The set of all compatible values is included in that, > irrespective of whether a particular value actually (currently) defines > a different HW interface or not. Well, I tend to agree on the principle, but so far it was never really done like that. That's not necessarily a good excuse, but if we start adding new bindings for the huge number of OMAP|AM variants TI has been introduced for 10 years, I'd rather use a wildcard than a exhaustive list of all the devices. Something like ti,[omap|am]*-timer for example . Regards, Benoit -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
