[PATCH 2/3] powerpc/esdhc: add property to disable the CMD23

[Kumar Gala]

On Sep 17, 2012, at 8:09 PM, Huang Changming-R66093 wrote:

>> On Sep 17, 2012, at 7:36 AM, Chris Ball wrote:
>> 
>>> Hi,
>>> 
>>> On Thu, Sep 13 2012, Kumar Gala wrote:
>>>>>> Can you list out which SoCs support it and which don't.  Having
>>>>>> this list will be useful in understanding which controller versions
>> supported it.
>>>>>> 
>>>>> P1020, p1021, p1022, p1024, p1015 and p4080 can't support it.
>>>>> Mpc8536, p2020, and the other current DPAA silicon (e.g. p5020, p3041)
>> support it.
>>>> 
>>>> Based on this, why don't we use the HOSTVER register to detect instead
>> of device tree:
>>> 
>>> I've got a mild preference for handling quirk assignment in the DT
>>> rather than in driver code, so I'd prefer to just push the original
>>> patch to mmc-next as-is.  Does that sound okay?
>> 
>> Why?  I only ask because I agree with Scott that this means you have to
>> update your device tree to get proper functionality.
>> 
> When the new silicon does not support CMD23,
> if we don't update the device tree, then we must update the SDHC driver.
> I prefer to add the property in device tree,
> because we just add this property in new device tree, we don't need more effort to modify driver.
> 

Jerry,

I think doing it driver makes more sense because:

1. means older device tree's still work
2. odds that CMD23 not being supported in future devices is near 0%
   (Now that we support AutoCMD23 [and thus CMD23] we aren't likely to stop supporting it in future)
3. If IP changes you are going to have to update driver anyways for new features

I really think we should NOT utilize device tree for this.

- k