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

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

Hi,

On 30-10-2025 02:07, Belgaumkar, Vinay wrote:
>
> On 10/29/2025 12:58 PM, Vivi, Rodrigo wrote:
>> On Thu, 2025-10-30 at 00:05 +0530, Anirban, Sk wrote:
>>> 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?
>> I think you need to get to the drawing board and think on another
>> proposal. This is becoming to get really messier.
>>
>> update_rp simply update them all before the actual get.
>>
>> you don't update another thing inside a get of a specific thing
>> of interest.
>>
>> think of what are the cases where the rpn update is really needed.
>> think if we should have a constant workqueue refreshing it if not
>> idle/suspended. Think about all the consequences of the updates
>> and removal that you are proposing. And always making sure that
>> that that igt freq test is reliably passing.
>>
>> But something is strange in the current proposal.
>
> Agreed. The issue was we needed to get updated RPe. Why do we need to 
> update RPn? That is a fused value and never changes. SLPC min freq 
> changes with RPe. So we need to ensure we read SLPC min every time (if 
> we are not doing that already).
>
> Thanks,
>
> Vinay.
>
In that case the current implementation of updating RPn wrt Rpe is not 
required anymore, I will remove that. So we will update RPe only & while 
reading
>>
>>> 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
>>>>>