On Mon, Jul 9, 2012 at 8:40 PM, Vincent Guittot
[off-list ref] wrote:

On 9 July 2012 16:37, Shilimkar, Santosh [off-list ref] wrote:

quoted

On Mon, Jul 9, 2012 at 8:06 PM, Vincent Guittot
[off-list ref] wrote:

quoted

On 9 July 2012 15:00, Shilimkar, Santosh [off-list ref] wrote:

quoted

On Mon, Jul 9, 2012 at 6:02 PM, Vincent Guittot
[off-list ref] wrote:

quoted

On 9 July 2012 12:55, Shilimkar, Santosh [off-list ref] wrote:

quoted

Vincent,
On Mon, Jul 9, 2012 at 2:57 PM, Vincent Guittot
[off-list ref] wrote:

quoted

Use cpu compatibility field and clock-frequency field of DT to
estimate the capacity of each core of the system and to update
the cpu_power field accordingly.
This patch enables to put more running tasks on big cores than
on LITTLE ones. But this patch doesn't ensure that long running
tasks will run on big cores and short ones on LITTLE cores.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
---
 arch/arm/kernel/topology.c |  153 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)

Sorry for not giving this comment on previous version but we should also
have a way to provide the big.LITTLE information without Device Tree.
May be a platform device/data.

Hi Santosh,

I had thought of adding such additional way to set cpu_power of
big.LITTLE but my conclusion was
-it's a new platform so it should come with DT
-DT is already required by other patches linked to big.LITTLE
(http://lists.infradead.org/pipermail/linux-arm-kernel/2012-January/080873.html)
-There is no device that can be easily used to get such information at
this early boot stage.

I see. Its new processor but it is just 1 one of the IP in an entire SOC.
As mentioned below I was talking about full SOC support including
all the driver subsystem with DT.

quoted

quoted

I know we are moving DT way, but remember apart from core kernel
infrastructure, to have a complete product build with DT means all the
drivers must be already supporting DT which is not the case with
many huge driver sub-systems like USB, display subsystem, Audio etc.

Having that support would greatly help for the SOC's which have not yet
reached to stage where entire SOC is DT compliant and want to use
big.LITTLE infrastructure.

Can't you support both type of devices on your platform ? You can move
your device to DT mode when it is supported ?

That is what eventually people end up doing who don't have
DT ready for entire SOC. I was trying to ask whether at least some
method is proposed(need not be merged in mainline) to have
the big.LITTLE information parsing without DT.

Ok, IIUC, you need a temporary methods, which doesn't need to be
merged in mainline, to set the cpu_scale field ?

Yep.

You could use set_power_scale in your platform code to set the
cpu_power of your CPUs until DT is ready for your platform.

Thanks for the clarification. Will try that out.

Regards
Santosh