On Mon, Jul 9, 2012 at 6:02 PM, Vincent Guittot vincent.guittot@linaro.org wrote:
On 9 July 2012 12:55, Shilimkar, Santosh santosh.shilimkar@ti.com wrote:
Vincent, On Mon, Jul 9, 2012 at 2:57 PM, Vincent Guittot vincent.guittot@linaro.org wrote:
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.ht...) -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.
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.
Regards Santosh