Tegra DRM device tree bindings

[Stephen Warren]

On 06/28/2012 12:18 AM, Hiroshi Doyu wrote:
> On Wed, 27 Jun 2012 16:44:14 +0200
> Thierry Reding <thierry.reding at avionic-design.de> wrote:
> 
>>> I think that "coherent_pool" can be used only when the amount of
>>> contiguous memory is short in your system. Otherwise even unnecessary.
>>>
>>> Could you explain a bit more why you want carveout size on per-board basis?
>>
>> In the ideal case I would want to not have a carveout size at all.
>> However there may be situations where you need to make sure some driver
>> can allocate a given amount of memory. Having to specify this using a
>> kernel command-line parameter is cumbersome because it may require
>> changes to the bootloader or whatever. So if you know that a particular
>> board always needs 128 MiB of carveout, then it makes sense to specify
>> it on a per-board basis.
> 
> Hm...I could understand somewhat;) but DT can also specify "bootargs"
> in dts file, which can support per-board-wide spec too, like the above
> sum of carveout needed from all drivers. I just want to avoid
> introducing a new parameter additionaly if we can make use of the
> existing mechanism.

The bootargs in the DT file is usually provided by (over-written by) the
bootloader. If we start requiring lots of random kernel command-line
arguments, that makes it more effort for the user of the bootloader
(e.g. distribution bootloader scripts, etc.) to create the kernel
command-line. I'd prefer to avoid that as much as possible. That said,
using a standardized command-line option that is (or will be) used by
all (ARM?) SoCs for the same purpose is reasonable, because there's
commonality there.