Re: [PATCH] drm/xe/guc: Eliminate RPe caching for SLPC parameter handling

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

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On 10/12/2025 11:42 PM, Sk Anirban wrote:
> RPe is runtime-determined by PCODE and caching it caused stale values,
> leading to incorrect GuC SLPC parameter settings.
> Drop the cached rpe_freq field and query fresh values from hardware
> on each use to ensure GuC SLPC parameters reflect current RPe.
>
> v2: Remove cached RPe frequency field (Rodrigo)
>
> Closes:https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5166
> Signed-off-by: Sk Anirban<sk.anirban@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_guc_pc.c       | 36 +++++++++++++++-------------
>   drivers/gpu/drm/xe/xe_guc_pc_types.h |  2 --
>   2 files changed, 20 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
> index 3c0feb50a1e2..2d1d5121555e 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc.c
> +++ b/drivers/gpu/drm/xe/xe_guc_pc.c
> @@ -330,7 +330,7 @@ static int pc_set_min_freq(struct xe_guc_pc *pc, u32 freq)
>   	 * Our goal is to have the admin choices respected.
>   	 */
>   	pc_action_set_param(pc, SLPC_PARAM_IGNORE_EFFICIENT_FREQUENCY,
> -			    freq < pc->rpe_freq);
> +			    freq < xe_guc_pc_get_rpe_freq(pc));
>   
>   	return pc_action_set_param(pc,
>   				   SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
> @@ -375,7 +375,7 @@ static void mtl_update_rpa_value(struct xe_guc_pc *pc)
>   	pc->rpa_freq = decode_freq(REG_FIELD_GET(MTL_RPA_MASK, reg));
>   }
>   
> -static void mtl_update_rpe_value(struct xe_guc_pc *pc)
> +static u32 mtl_get_rpe_value(struct xe_guc_pc *pc)
while we are here, can we rename these local functions to 
mtl_get_rpe_*freq*() and tgl_get_rpe_*freq*(), since both these 
functions return the decoded freq?
>   {
>   	struct xe_gt *gt = pc_to_gt(pc);
>   	u32 reg;
> @@ -385,7 +385,7 @@ static void mtl_update_rpe_value(struct xe_guc_pc *pc)
>   	else
>   		reg = xe_mmio_read32(&gt->mmio, MTL_GT_RPE_FREQUENCY);
>   
> -	pc->rpe_freq = decode_freq(REG_FIELD_GET(MTL_RPE_MASK, reg));
> +	return decode_freq(REG_FIELD_GET(MTL_RPE_MASK, reg));
>   }
>   
>   static void tgl_update_rpa_value(struct xe_guc_pc *pc)
> @@ -408,7 +408,7 @@ static void tgl_update_rpa_value(struct xe_guc_pc *pc)
>   	}
>   }
>   
> -static void tgl_update_rpe_value(struct xe_guc_pc *pc)
> +static u32 tgl_get_rpe_value(struct xe_guc_pc *pc)
>   {
>   	struct xe_gt *gt = pc_to_gt(pc);
>   	struct xe_device *xe = gt_to_xe(gt);
> @@ -421,10 +421,10 @@ static void tgl_update_rpe_value(struct xe_guc_pc *pc)
>   	 */
>   	if (xe->info.platform == XE_PVC) {
>   		reg = xe_mmio_read32(&gt->mmio, PVC_RP_STATE_CAP);
> -		pc->rpe_freq = REG_FIELD_GET(RP1_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
> +		return REG_FIELD_GET(RP1_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
>   	} else {
>   		reg = xe_mmio_read32(&gt->mmio, FREQ_INFO_REC);
> -		pc->rpe_freq = REG_FIELD_GET(RPE_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
> +		return REG_FIELD_GET(RPE_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
>   	}
>   }
>   
> @@ -433,20 +433,17 @@ static void pc_update_rp_values(struct xe_guc_pc *pc)
>   	struct xe_gt *gt = pc_to_gt(pc);
>   	struct xe_device *xe = gt_to_xe(gt);
>   
> -	if (GRAPHICS_VERx100(xe) >= 1270) {
> +	if (GRAPHICS_VERx100(xe) >= 1270)
>   		mtl_update_rpa_value(pc);
> -		mtl_update_rpe_value(pc);
> -	} else {
> +	else
>   		tgl_update_rpa_value(pc);
> -		tgl_update_rpe_value(pc);
> -	}
>   
>   	/*
>   	 * RPe is decided at runtime by PCODE. In the rare case where that's
>   	 * smaller than the fused min, we will trust the PCODE and use that
>   	 * as our minimum one.
>   	 */
> -	pc->rpn_freq = min(pc->rpn_freq, pc->rpe_freq);
> +	pc->rpn_freq = min(pc->rpn_freq, xe_guc_pc_get_rpe_freq(pc));
>   }
>   
>   /**
> @@ -560,9 +557,16 @@ u32 xe_guc_pc_get_rpa_freq(struct xe_guc_pc *pc)
>    */
>   u32 xe_guc_pc_get_rpe_freq(struct xe_guc_pc *pc)
>   {
> -	pc_update_rp_values(pc);
> +	struct xe_gt *gt = pc_to_gt(pc);
> +	struct xe_device *xe = gt_to_xe(gt);
> +	u32 rpe_freq;
> +
> +	if (GRAPHICS_VERx100(xe) >= 1270)
> +		rpe_freq = mtl_get_rpe_value(pc);

just return mtl_get_rpe_value(pc) instead of storing in a local var?

Other than that,

LGTM,

Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>

> +	else
> +		rpe_freq = tgl_get_rpe_value(pc);
>   
> -	return pc->rpe_freq;
> +	return rpe_freq;
>   }
>   
>   /**
> @@ -1021,7 +1025,7 @@ static int pc_set_mert_freq_cap(struct xe_guc_pc *pc)
>   	/*
>   	 * Ensure min and max are bound by MERT_FREQ_CAP until driver loads.
>   	 */
> -	ret = pc_set_min_freq(pc, min(pc->rpe_freq, pc_max_freq_cap(pc)));
> +	ret = pc_set_min_freq(pc, min(xe_guc_pc_get_rpe_freq(pc), pc_max_freq_cap(pc)));
>   	if (!ret)
>   		ret = pc_set_max_freq(pc, min(pc->rp0_freq, pc_max_freq_cap(pc)));
>   
> @@ -1339,7 +1343,7 @@ static void xe_guc_pc_fini_hw(void *arg)
>   	XE_WARN_ON(xe_guc_pc_stop(pc));
>   
>   	/* Bind requested freq to mert_freq_cap before unload */
> -	pc_set_cur_freq(pc, min(pc_max_freq_cap(pc), pc->rpe_freq));
> +	pc_set_cur_freq(pc, min(pc_max_freq_cap(pc), xe_guc_pc_get_rpe_freq(pc)));
>   
>   	xe_force_wake_put(gt_to_fw(pc_to_gt(pc)), fw_ref);
>   }
> diff --git a/drivers/gpu/drm/xe/xe_guc_pc_types.h b/drivers/gpu/drm/xe/xe_guc_pc_types.h
> index 5e4ea53fbee6..f27c05d81706 100644
> --- a/drivers/gpu/drm/xe/xe_guc_pc_types.h
> +++ b/drivers/gpu/drm/xe/xe_guc_pc_types.h
> @@ -21,8 +21,6 @@ struct xe_guc_pc {
>   	u32 rp0_freq;
>   	/** @rpa_freq: HW RPa frequency - The Achievable one */
>   	u32 rpa_freq;
> -	/** @rpe_freq: HW RPe frequency - The Efficient one */
> -	u32 rpe_freq;
>   	/** @rpn_freq: HW RPN frequency - The Minimum one */
>   	u32 rpn_freq;
>   	/** @user_requested_min: Stash the minimum requested freq by user */

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