Re: [PATCH v5 1/2] drm/xe/guc: Eliminate RPe caching for SLPC parameter handling

["Anirban, Sk" <sk.anirban@intel.com>]

Hi,

On 29-10-2025 23:34, Rodrigo Vivi wrote:
> On Wed, Oct 29, 2025 at 04:50:16PM +0530, 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)
>> v3: Remove extra variable (Vinay)
>>      Modify function name (Vinay)
>> v4: Maintain a separate function for PVC (Rodrigo)
>> v5: Update RPn while fetching RPe frequency
>>
>> 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       | 75 ++++++++++++++++------------
>>   drivers/gpu/drm/xe/xe_guc_pc_types.h |  2 -
>>   2 files changed, 42 insertions(+), 35 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_guc_pc.c b/drivers/gpu/drm/xe/xe_guc_pc.c
>> index 3c0feb50a1e2..08deaa64aa85 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_freq(struct xe_guc_pc *pc)
>>   {
>>   	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)
>> @@ -408,24 +408,22 @@ static void tgl_update_rpa_value(struct xe_guc_pc *pc)
>>   	}
>>   }
>>   
>> -static void tgl_update_rpe_value(struct xe_guc_pc *pc)
>> +static u32 pvc_get_rpe_freq(struct xe_guc_pc *pc)
>>   {
>>   	struct xe_gt *gt = pc_to_gt(pc);
>> -	struct xe_device *xe = gt_to_xe(gt);
>>   	u32 reg;
>>   
>> -	/*
>> -	 * For PVC we still need to use fused RP1 as the approximation for RPe
>> -	 * For other platforms than PVC we get the resolved RPe directly from
>> -	 * PCODE at a different register
>> -	 */
>> -	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;
>> -	} else {
>> -		reg = xe_mmio_read32(&gt->mmio, FREQ_INFO_REC);
>> -		pc->rpe_freq = REG_FIELD_GET(RPE_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
>> -	}
>> +	reg = xe_mmio_read32(&gt->mmio, PVC_RP_STATE_CAP);
>> +	return REG_FIELD_GET(RP1_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
>> +}
>> +
>> +static u32 tgl_get_rpe_freq(struct xe_guc_pc *pc)
>> +{
>> +	struct xe_gt *gt = pc_to_gt(pc);
>> +	u32 reg;
>> +
>> +	reg = xe_mmio_read32(&gt->mmio, FREQ_INFO_REC);
>> +	return REG_FIELD_GET(RPE_MASK, reg) * GT_FREQUENCY_MULTIPLIER;
>>   }
>>   
>>   static void pc_update_rp_values(struct xe_guc_pc *pc)
>> @@ -433,20 +431,10 @@ 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);
>>   }
>>   
>>   /**
>> @@ -560,9 +548,30 @@ 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 freq;
>>   
>> -	return pc->rpe_freq;
>> +	/*
>> +	 * For PVC we still need to use fused RP1 as the approximation for RPe
>> +	 * For other platforms than PVC we get the resolved RPe directly from
>> +	 * PCODE at a different register
>> +	 */
>> +	if (xe->info.platform == XE_PVC)
> I believe it would be better to convert this to the graphics version here
> instead of the platform name. But no block since it was already a platform check
> above.
sure, I will look into this.
>> +		freq = pvc_get_rpe_freq(pc);
>> +	else if (GRAPHICS_VERx100(xe) >= 1270)
>> +		freq = mtl_get_rpe_freq(pc);
>> +	else
>> +		freq = tgl_get_rpe_freq(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, freq);
> setting rpn_freq inside this get_rpe function makes no sense.
>
> I'm sorry I forgot about this when I told you to kill the other function.
> It should stay there, but be called update_rpn instead...
Since RPn updates depend on RPe, my intention was to update RPn whenever 
RPe is fetched.
Alternatively, I can maintain a separate update_rpn() function, but in 
either case, it will be invoked during initialization and while 
retrieving RPe frequencies.
Another option could be to simply rename the function to 
xe_guc_pc_get_rpe_rpn_freq() to reflect its dual purpose.
What are your thoughts on this approach?

Thanks,
Anirban
>> +
>> +	return freq;
>>   }
>>   
>>   /**
>> @@ -1021,7 +1030,7 @@ 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 +1348,7 @@ 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 */
>> -- 
>> 2.43.0
>>