[Skiboot] [PATCH v2] SLW: Remove stop1_lite and stop2_lite

[Balbir Singh]

On Wed, May 23, 2018 at 6:17 PM, Akshay Adiga
<akshay.adiga at linux.vnet.ibm.com> wrote:
> stop1_lite has been removed since it adds no additional benefit
> over stop0_lite. stop2_lite has been removed since currently it adds
> minimal benefit over stop2. However, the benefit is eclipsed by the time
> required to ungate the clocks
>
> Moreover, Lite states don't give up the SMT resources, can potentially
> have a performance impact on sibling threads.
>
> Signed-off-by: Akshay Adiga <akshay.adiga at linux.vnet.ibm.com>
> ---
>  hw/slw.c | 36 ++++++++----------------------------
>  1 file changed, 8 insertions(+), 28 deletions(-)
>
> diff --git a/hw/slw.c b/hw/slw.c
> index 2b305db..ff6e2a4 100644
> --- a/hw/slw.c
> +++ b/hw/slw.c
> @@ -529,20 +529,9 @@ static struct cpu_idle_states power9_cpu_idle_states[] = {
>                                  | OPAL_PM_PSSCR_ESL \
>                                  | OPAL_PM_PSSCR_EC,
>                 .pm_ctrl_reg_mask = OPAL_PM_PSSCR_MASK },
> -       {
> -               .name = "stop1_lite", /* Enter stop1 with no state loss */
> -               .latency_ns = 4900,
> -               .residency_ns = 49000,

How did we come up with the latency and residency values for
stop1_lite, stop2_lite? It sounds like the values are roughtly 2% of
the corresponding non lite states? Are these values empirical,
guesses, retrofitted to the OS?

Balbir Singh