Re: [PATCH 2/3] drm/xe/lnl: Enable GuC SLPC DCC task

["Belgaumkar, Vinay" <vinay.belgaumkar@intel.com>]

On 10/9/2024 11:36 AM, Rodrigo Vivi wrote:
> Enable DCC (Duty Cycle Control) in Lunar Lake.
>
> DCC is the SLPC task that tries to keep
> the GT from operating inefficiently when thermally constrained.
>
> Although the recommendation is to enable it, LNL GuC is leaving
> it disabled by default on LNL.
>
> It would minimize the GT frequency oscilation on throttled
> scenarios, what could potentially reduce latencies.
>
> Cc: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_guc_pc.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
> index 4b38523c49e9..d141165e016b 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
> @@ -948,6 +948,16 @@ static int pc_init_freqs(struct xe_guc_pc *pc)
>   	return ret;
>   }
>   
> +static int slpc_set_policies(struct xe_guc_pc *pc)
> +{
> +	struct xe_device *xe = pc_to_xe(pc);
> +
> +	if (xe->info.platform == XE_LUNARLAKE)
> +		return pc_action_set_param(pc, SLPC_PARAM_TASK_ENABLE_DCC, 1);
> +
> +	return 0;
> +}
> +
>   /**
>    * xe_guc_pc_start - Start GuC's Power Conservation component
>    * @pc: Xe_GuC_PC instance
> @@ -983,6 +993,10 @@ int xe_guc_pc_start(struct xe_guc_pc *pc)
>   	if (ret)
>   		goto out;
>   
> +	ret = slpc_set_policies(pc);
> +	if (ret)
> +		goto out;
> +

Might be better to call set_policies after the wait_for_pc_state below? 
Since we just did a reset. Although, pc_action_set_param() also does a 
wait for running state, so we have some redundancy here.

Thanks,

Vinay,

>   	if (wait_for_pc_state(pc, SLPC_GLOBAL_STATE_RUNNING)) {
>   		xe_gt_err(gt, "GuC PC Start failed\n");
>   		ret = -EIO;