On Mon, 16 May 2022, Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx> wrote:
> On Sat, 14 May 2022, Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx> wrote:
>> SLPC min/max frequency updates require H2G calls. We are seeing
>> timeouts when GuC channel is backed up and it is unable to respond
>> in a timely fashion causing warnings and affecting CI.
>>
>> This is seen when waitboosting happens during a stress test.
>> this patch updates the waitboost path to use a non-blocking
>> H2G call instead, which returns as soon as the message is
>> successfully transmitted.
>>
>> v2: Use drm_notice to report any errors that might occur while
>> sending the waitboost H2G request (Tvrtko)
>>
>> Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c | 44 +++++++++++++++++----
>> 1 file changed, 36 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
>> index 1db833da42df..e5e869c96262 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c
>> @@ -98,6 +98,30 @@ static u32 slpc_get_state(struct intel_guc_slpc *slpc)
>> return data->header.global_state;
>> }
>>
>> +static int guc_action_slpc_set_param_nb(struct intel_guc *guc, u8 id, u32 value)
>> +{
>> + u32 request[] = {
>
> static const
*sigh*
-ENOCOFFEE, please ignore the mail.
BR,
Jani.
>
>> + GUC_ACTION_HOST2GUC_PC_SLPC_REQUEST,
>> + SLPC_EVENT(SLPC_EVENT_PARAMETER_SET, 2),
>> + id,
>> + value,
>> + };
>> + int ret;
>> +
>> + ret = intel_guc_send_nb(guc, request, ARRAY_SIZE(request), 0);
>> +
>> + return ret > 0 ? -EPROTO : ret;
>> +}
>> +
>> +static int slpc_set_param_nb(struct intel_guc_slpc *slpc, u8 id, u32 value)
>> +{
>> + struct intel_guc *guc = slpc_to_guc(slpc);
>> +
>> + GEM_BUG_ON(id >= SLPC_MAX_PARAM);
>> +
>> + return guc_action_slpc_set_param_nb(guc, id, value);
>> +}
>> +
>> static int guc_action_slpc_set_param(struct intel_guc *guc, u8 id, u32 value)
>> {
>> u32 request[] = {
>
> Ditto here, and the whole gt/uc directory seems to have tons of these
> u32 action/request array variables on stack, with the required
> initialization, that could be in rodata.
>
> Please fix all of them.
>
> BR,
> Jani.
>
>> @@ -208,12 +232,10 @@ static int slpc_force_min_freq(struct intel_guc_slpc *slpc, u32 freq)
>> */
>>
>> with_intel_runtime_pm(&i915->runtime_pm, wakeref) {
>> - ret = slpc_set_param(slpc,
>> - SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
>> - freq);
>> - if (ret)
>> - i915_probe_error(i915, "Unable to force min freq to %u: %d",
>> - freq, ret);
>> + /* Non-blocking request will avoid stalls */
>> + ret = slpc_set_param_nb(slpc,
>> + SLPC_PARAM_GLOBAL_MIN_GT_UNSLICE_FREQ_MHZ,
>> + freq);
>> }
>>
>> return ret;
>> @@ -222,6 +244,8 @@ static int slpc_force_min_freq(struct intel_guc_slpc *slpc, u32 freq)
>> static void slpc_boost_work(struct work_struct *work)
>> {
>> struct intel_guc_slpc *slpc = container_of(work, typeof(*slpc), boost_work);
>> + struct drm_i915_private *i915 = slpc_to_i915(slpc);
>> + int err;
>>
>> /*
>> * Raise min freq to boost. It's possible that
>> @@ -231,8 +255,12 @@ static void slpc_boost_work(struct work_struct *work)
>> */
>> mutex_lock(&slpc->lock);
>> if (atomic_read(&slpc->num_waiters)) {
>> - slpc_force_min_freq(slpc, slpc->boost_freq);
>> - slpc->num_boosts++;
>> + err = slpc_force_min_freq(slpc, slpc->boost_freq);
>> + if (!err)
>> + slpc->num_boosts++;
>> + else
>> + drm_notice(&i915->drm, "Failed to send waitboost request (%d)\n",
>> + err);
>> }
>> mutex_unlock(&slpc->lock);
>> }
--
Jani Nikula, Intel Open Source Graphics Center
