[PATCH] s5pv210: Change the base ram address to 0x3000'0000

[Ben Dooks]

On Fri, May 28, 2010 at 11:35:59AM +0900, Kyungmin Park wrote:
> s5pc110 (aka s5pv210) has 2 DRAM port and used it both usually.
> Assume DMC0 starts with 0x2000'0000 with 128MiB.
> DMC1 starts with 0x4000'0000 with 128MiB.
> Note that DMC1 has to start address 0x4000'0000 at least.
> 
> Then there's too much memory hole 0x1800'0000 (128MiB + 256MiB)
> 
> To reduce memory waste, the DMC0 start with 0x3000'0000.
> 
> Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
> ---
> diff --git a/arch/arm/mach-s5pv210/Makefile.boot b/arch/arm/mach-s5pv210/Makefile.boot
> index ff90aa1..b0909e3 100644
> --- a/arch/arm/mach-s5pv210/Makefile.boot
> +++ b/arch/arm/mach-s5pv210/Makefile.boot
> @@ -1,2 +1,2 @@
> -   zreladdr-y	:= 0x20008000
> -params_phys-y	:= 0x20000100
> +   zreladdr-y	:= 0x30008000
> +params_phys-y	:= 0x30000100

Apart from the technical comments that have been in this thread, I would
like to share notes about making changes like these that affect the entire
SoC kernel build.

Firstly, changing this effects the rest of the users, not everyone is
using the same device with same layout. This configuration boots on
both S5PC110 and S5PV210 devices. Some of these _have_ to support 1GiB
of memory. Some of them have their bootloaders programemd to start at
0x20... So please think of how this will affect everyone else.

Secondly, if you have thought about point 1, then please let us know in
the commit messages.  The commit message isn't just a log of what the
patch does, it can also be used to show any necessary working about what
is happening and side-effects of it.

Thirdly, the kernel's default configuration for a SoC/arch isn't meant to 
be the best-fit for your board(s) or development practicies. It is meant
to cover as many devices as possible, to allow build testing and to have
something that people can test with. If it is not the most efficient on
the board, then make your own defconfig that is a best fit for your
purposes.

So, sometimes when this sort of change is required there may be a case of
making it configurable so that your own defconfig/boardconfig can select
it for your own projects.


Please keep in mind that other people have/are using the kernel and that
some changes have an affect on other projects as well as your own. This
is why user-space facing changes are the most debated and difficult to
do, kernel internals shift quite easily, whilst the data exported to
userspace is kept as stable as possible.

-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.