[PATCH v2 3/5] dt/bindings: ti, edma: Remove redundant properties from documentation

Sekhar Nori nsekhar at ti.com
Thu May 15 02:00:23 PDT 2014

+ DT bindings maintainers

On Thursday 15 May 2014 01:48 PM, Peter Ujfalusi wrote:
> On 05/15/2014 11:01 AM, Arnd Bergmann wrote:
>> On Tuesday 13 May 2014 13:30:30 Peter Ujfalusi wrote:
>>> From CCCFG register of eDMA3 we can get all the needed information for the
>>> driver about the IP:
>>> Number of channels: NUM_DMACH
>>> Number of regions: NUM_REGN
>>> Number of slots (PaRAM sets): NUM_PAENTRY
>>> Number of TC/EQ: NUM_EVQUE
>>> The ti,edma-regions; ti,edma-slots and dma-channels in DT are
>>> redundant since the very same information can be obtained from the HW.
>>> The mentioned properties can be removed from the binding document.
>>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
>> I wonder if we should keep them listed as "optional" properties so you
>> can have a dtb file that still works with older kernels which need them.
>> What you do is an incompatible change to the binding, which we shouldn't
>> do lightly. Any new dts files don't need this information of course, but
>> as a general rule, I'd rather keep things like this around unless we
>> already have to enforce an ABI break that is well documented.
> We could keep them as optional, or to be precise: ignored properties since we
> are not going to even look at them in the future.
> But I do not really see the reason to do so. With this change new kernels will
> boot with old DTB - if it can not be changed which I have not seen yet. Sure
> old kernel would not boot with this change, but why would you downgrade the
> kernel and update the DTB on a board?
> Bisecting is not a good reason since the bug you might be hunting for could be
> in the DTS or in the kernel code so you need to update both of them to be sure
> you reach the commit you are looking for.

Agree with Peter here. The bisecting corner case can hopefully be
handled by appended DTB even if the original DTB was ROMed.


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