[Intel-gfx] [RFC PATCH 15/97] drm/i915/guc: Relax CTB response timeout

[Michal Wajdeczko]

On 25.05.2021 20:08, Matthew Brost wrote:
> On Thu, May 06, 2021 at 12:13:29PM -0700, Matthew Brost wrote:
>> From: Michal Wajdeczko <michal.wajdeczko at intel.com>
>>
>> In upcoming patch we will allow more CTB requests to be sent in
>> parallel to the GuC for procesing, so we shouldn't assume any more
>> that GuC will always reply without 10ms.
>>
>> Use bigger value from CONFIG_DRM_I915_HEARTBEAT_INTERVAL instead.
>>
> 
> I think this should be its own config option or we combine it with a
> config option suggested in patch 37.
> 
> What do you think Michal? If you agree I can fix this up in the post of
> these patches.

+ Tvrtko

yep, use of dedicated GuC CONFIG is what we also agree internally,
existing HEARTBEAT_INTERVAL was just fastest way to bypass 10ms

so, yes, please go ahead and do it right

> 
> Matt
> 
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko at intel.com>
>> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
>> ---
>>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> index c87a0a8bef26..a4b2e7fe318b 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> @@ -436,17 +436,23 @@ static int ct_write(struct intel_guc_ct *ct,
>>   */
>>  static int wait_for_ct_request_update(struct ct_request *req, u32 *status)
>>  {
>> +	long timeout;
>>  	int err;
>>  
>>  	/*
>>  	 * Fast commands should complete in less than 10us, so sample quickly
>>  	 * up to that length of time, then switch to a slower sleep-wait loop.
>>  	 * No GuC command should ever take longer than 10ms.
>> +	 *
>> +	 * However, there might be other CT requests in flight before this one,
>> +	 * so use @CONFIG_DRM_I915_HEARTBEAT_INTERVAL as backup timeout value.
>>  	 */
>> +	timeout = max(10, CONFIG_DRM_I915_HEARTBEAT_INTERVAL);
>> +
>>  #define done INTEL_GUC_MSG_IS_RESPONSE(READ_ONCE(req->status))
>>  	err = wait_for_us(done, 10);
>>  	if (err)
>> -		err = wait_for(done, 10);
>> +		err = wait_for(done, timeout);
>>  #undef done
>>  
>>  	if (unlikely(err))
>> -- 
>> 2.28.0
>>
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