[Skiboot] [PATCH] occ: Skip setting cores to nominal frequency in P9

[Vaidyanathan Srinivasan]

* Shilpa Bhat <shilpa.bhat at linux.vnet.ibm.com> [2017-04-01 14:59:39]:

> In P9, once OCC is up, it is supposed to setup the cores to nominal
> frequency. So skip this step in OPAL.
> 
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat at linux.vnet.ibm.com>
Acked-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
Tested-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>

> ---
>  hw/occ.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)

Tested on Zaius platform.  OCC is enabled and we need the following
patch to skip setting nominal frequency in skiboot. This will be done
by OCC on P9 and future platforms.

We save few 10s of milli-seconds in bootup where we have to do xscoms
and wait for transitions and switch control back to host.  This task
is best done by OCC when it boots up.

--Vaidy

> diff --git a/hw/occ.c b/hw/occ.c
> index 2ffb677..b222521 100644
> --- a/hw/occ.c
> +++ b/hw/occ.c
> @@ -897,11 +897,14 @@ void occ_pstates_init(void)
>  		return;
>  	}
> 
> -	/* Setup host based pstates and set nominal frequency */
> -	for_each_chip(chip) {
> -		for_each_available_core_in_chip(c, chip->id) {
> -			cpu_pstates_prepare_core(chip, c, pstate_nom);
> -		}
> +	/*
> +	 * Setup host based pstates and set nominal frequency only in
> +	 * P8.
> +	 */
> +	if (proc_gen == proc_gen_p8) {
> +		for_each_chip(chip)
> +			for_each_available_core_in_chip(c, chip->id)
> +				cpu_pstates_prepare_core(chip, c, pstate_nom);
>  	}
> 
>  	/* Add opal_poller to poll OCC throttle status of each chip */
> -- 
> 1.8.3.1
>