[U-Boot] [PATCH 3/3] mx6sl: Add initial support for mx6slevk board

[Dirk Behme]

Am 06.04.2013 16:15, schrieb Fabio Estevam:
> On Sat, Apr 6, 2013 at 10:52 AM, Dirk Behme <dirk.behme at gmail.com> wrote:
>
>> Most probably it would be sufficient to enable only the clocks needed for
>> booting ;) And not all clocks. On the other boards we do
>>
>> /* set the default clock gate to save power */
>> DATA 4 0x020c4068 0x00C03F3F
>> DATA 4 0x020c406c 0x0030FC03
>> DATA 4 0x020c4070 0x0FFFC000
>> DATA 4 0x020c4074 0x3FF00000
>> DATA 4 0x020c4078 0x00FFF300
>> DATA 4 0x020c407c 0x0F0000C3
>> DATA 4 0x020c4080 0x000003FF
>>
>> http://git.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=blob;f=board/freescale/imx/ddr/mx6q_4x_mt41j128.cfg;h=f4cae5eeb9899ab4ba937ae286e004d6861f1d43;hb=refs/heads/master#l161
>>
>> Do you like to try anything similar here, too?
>
> No, sorry. It is possible to turn some clocks off, for sure,  but I do
> not see real benefit by doing this on this solo-lite board.
>
> U-boot runs only for few seconds (or ms), so not much of power savings
> we can do in the bootloader.

To my understanding what we do above is not about saving power in the 
bootloader ...

> I am just setting the clocks to the default states, so it is up to the
> kernel to manage the clocks as needed.

... but saving power over the whole (kernel) runtime. I might be 
wrong, but to my understanding the kernel doesn't *disable* unneeded 
clocks?

So it's up to the bootloader to enable only the peripherals (clocks) 
really needed for booting. And then it's up to the kernel's driver 
init functions to enable the needed clocks for the subsystem once it's 
needed.

But as I won't use this board I won't care about the power consumption 
here. If you think it's fine for the use cases of this board to enable 
all clocks by default, then this shouldn't stop applying this patch.

Best regards

Dirk