Tegra DRM device tree bindings

Thierry Reding thierry.reding at avionic-design.de
Sat Jun 30 11:04:13 PDT 2012


On Thu, Jun 28, 2012 at 10:46:58AM -0600, Stephen Warren wrote:
> 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.

I propose we stick with the default CMA settings for now and see where
we end up. No need to jump the gun.

Thierry
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