From: swarren@wwwdotorg•org (Stephen Warren)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer
Date: Wed, 29 May 2013 09:27:28 -0600 [thread overview]
Message-ID: <51A61E60.4070708@wwwdotorg.org> (raw)
In-Reply-To: <51A5BEB6.6070809@ti.com>
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.
next prev parent reply other threads:[~2013-05-29 15:27 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-27 14:33 [PATCH v2 00/14] ARM: OMAP2+: AM43x initial support Afzal Mohammed
2013-05-27 14:35 ` [PATCH v2 01/14] ARM: OMAP2+: separate out OMAP4 restart Afzal Mohammed
2013-05-27 14:35 ` [PATCH v2 02/14] ARM: OMAP2+: AM43x: Kconfig Afzal Mohammed
2013-06-12 17:12 ` Tony Lindgren
2013-06-13 6:58 ` Mohammed, Afzal
2013-06-13 9:54 ` Tony Lindgren
2013-06-13 10:02 ` Mohammed, Afzal
2013-06-13 10:17 ` Tony Lindgren
2013-05-27 14:35 ` [PATCH v2 03/14] ARM: OMAP2+: AM43x: kbuild Afzal Mohammed
2013-05-27 14:35 ` [PATCH v2 04/14] ARM: OMAP2+: AM43x: soc_is support Afzal Mohammed
2013-05-27 14:36 ` [PATCH v2 05/14] ARM: OMAP2+: AM437x: SoC revision detection Afzal Mohammed
2013-05-27 14:36 ` [PATCH v2 06/14] ARM: OMAP2+: AM43x: static mapping Afzal Mohammed
2013-05-27 14:36 ` [PATCH v2 07/14] ARM: OMAP2+: AM43x: early init Afzal Mohammed
2013-06-12 17:14 ` Tony Lindgren
2013-05-27 14:36 ` [PATCH v2 08/14] ARM: OMAP2+: AM43x: GP or HS ? Afzal Mohammed
2013-05-27 14:36 ` [PATCH v2 09/14] ARM: OMAP2+: AM43x: SRAM base and size Afzal Mohammed
2013-05-27 14:36 ` [PATCH v2 10/14] ARM: OMAP2+: AM43x: basic dt support Afzal Mohammed
2013-05-27 14:37 ` [PATCH v2 11/14] Documentation: dt: binding: omap: am43x timer Afzal Mohammed
2013-05-28 21:25 ` Jon Hunter
2013-05-28 22:05 ` Stephen Warren
2013-05-29 8:06 ` Mohammed, Afzal
2013-05-29 8:39 ` Benoit Cousson
2013-05-29 9:58 ` Mohammed, Afzal
2013-05-29 13:35 ` Benoit Cousson
2013-06-03 7:49 ` Mohammed, Afzal
2013-06-03 9:53 ` Benoit Cousson
2013-05-29 15:27 ` Stephen Warren [this message]
2013-05-30 11:44 ` Benoit Cousson
2013-05-29 20:17 ` Jon Hunter
2013-05-27 14:37 ` [PATCH v2 12/14] Documentation: dt: binding: omap: am43x counter Afzal Mohammed
2013-05-28 21:26 ` Jon Hunter
2013-05-29 8:08 ` Mohammed, Afzal
2013-05-27 14:37 ` [PATCH v2 13/14] Documentation: dt: binding: serial: omap: am43x Afzal Mohammed
2013-05-27 14:37 ` [PATCH v2 14/14] ARM: dts: AM43x: initial support Afzal Mohammed
2013-05-29 8:53 ` Benoit Cousson
2013-05-29 8:57 ` Florian Vaussard
2013-05-29 9:05 ` Benoit Cousson
2013-06-04 11:25 ` [PATCH v2 00/14] ARM: OMAP2+: AM43x " Mohammed, Afzal
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