Re: [Intel-gfx] [RFC PATCH 18/97] drm/i915/guc: Don't receive all G2H messages in irq handler

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On 25.05.2021 20:15, Matthew Brost wrote:
> On Thu, May 06, 2021 at 12:13:32PM -0700, Matthew Brost wrote:
>> From: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
>>
>> In irq handler try to receive just single G2H message, let other
>> messages to be received from tasklet.
>>
>> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
>> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
>> ---
>>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 67 ++++++++++++++++-------
>>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h |  3 +
>>  2 files changed, 50 insertions(+), 20 deletions(-)
>>
>> 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 cb58fa7f970c..d630ec32decf 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
>> @@ -81,6 +81,7 @@ enum { CTB_SEND = 0, CTB_RECV = 1 };
>>  
>>  enum { CTB_OWNER_HOST = 0 };
>>  
>> +static void ct_receive_tasklet_func(unsigned long data);
>>  static void ct_incoming_request_worker_func(struct work_struct *w);
>>  
>>  /**
>> @@ -95,6 +96,7 @@ void intel_guc_ct_init_early(struct intel_guc_ct *ct)
>>  	INIT_LIST_HEAD(&ct->requests.pending);
>>  	INIT_LIST_HEAD(&ct->requests.incoming);
>>  	INIT_WORK(&ct->requests.worker, ct_incoming_request_worker_func);
>> +	tasklet_init(&ct->receive_tasklet, ct_receive_tasklet_func, (unsigned long)ct);
> 
> This function is deprecated. tasklet_setup should be used.
> I can fix this up when I post the CTB patches.

I didn't notice that, but yes, passing struct to callback will be
cleaner, so please fix it

Thanks,
Michal

> 
>>  }
>>  
>>  static inline const char *guc_ct_buffer_type_to_str(u32 type)
>> @@ -244,6 +246,7 @@ void intel_guc_ct_fini(struct intel_guc_ct *ct)
>>  {
>>  	GEM_BUG_ON(ct->enabled);
>>  
>> +	tasklet_kill(&ct->receive_tasklet);
>>  	i915_vma_unpin_and_release(&ct->vma, I915_VMA_RELEASE_MAP);
>>  	memset(ct, 0, sizeof(*ct));
>>  }
>> @@ -629,7 +632,7 @@ static int ct_read(struct intel_guc_ct *ct, u32 *data)
>>  	CT_DEBUG(ct, "received %*ph\n", 4 * len, data);
>>  
>>  	desc->head = head * 4;
>> -	return 0;
>> +	return available - len;
>>  
>>  corrupted:
>>  	CT_ERROR(ct, "Corrupted descriptor addr=%#x head=%u tail=%u size=%u\n",
>> @@ -665,10 +668,10 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)
>>  	u32 status;
>>  	u32 datalen;
>>  	struct ct_request *req;
>> +	unsigned long flags;
>>  	bool found = false;
>>  
>>  	GEM_BUG_ON(!ct_header_is_response(header));
>> -	GEM_BUG_ON(!in_irq());
>>  
>>  	/* Response payload shall at least include fence and status */
>>  	if (unlikely(len < 2)) {
>> @@ -688,7 +691,7 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)
>>  
>>  	CT_DEBUG(ct, "response fence %u status %#x\n", fence, status);
>>  
>> -	spin_lock(&ct->requests.lock);
>> +	spin_lock_irqsave(&ct->requests.lock, flags);
>>  	list_for_each_entry(req, &ct->requests.pending, link) {
>>  		if (unlikely(fence != req->fence)) {
>>  			CT_DEBUG(ct, "request %u awaits response\n",
>> @@ -707,7 +710,7 @@ static int ct_handle_response(struct intel_guc_ct *ct, const u32 *msg)
>>  		found = true;
>>  		break;
>>  	}
>> -	spin_unlock(&ct->requests.lock);
>> +	spin_unlock_irqrestore(&ct->requests.lock, flags);
>>  
>>  	if (!found)
>>  		CT_ERROR(ct, "Unsolicited response %*ph\n", msgsize, msg);
>> @@ -821,31 +824,55 @@ static int ct_handle_request(struct intel_guc_ct *ct, const u32 *msg)
>>  	return 0;
>>  }
>>  
>> +static int ct_receive(struct intel_guc_ct *ct)
>> +{
>> +	u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
>> +	unsigned long flags;
>> +	int ret;
>> +
>> +	spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
>> +	ret = ct_read(ct, msg);
>> +	spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if (ct_header_is_response(msg[0]))
>> +		ct_handle_response(ct, msg);
>> +	else
>> +		ct_handle_request(ct, msg);
>> +
>> +	return ret;
>> +}
>> +
>> +static void ct_try_receive_message(struct intel_guc_ct *ct)
>> +{
>> +	int ret;
>> +
>> +	if (GEM_WARN_ON(!ct->enabled))
>> +		return;
>> +
>> +	ret = ct_receive(ct);
>> +	if (ret > 0)
>> +		tasklet_hi_schedule(&ct->receive_tasklet);
>> +}
>> +
>> +static void ct_receive_tasklet_func(unsigned long data)
>> +{
> 
> As mentioned above tasklet_init is deprecated. The callback now accepts
> the tasklet structure and ct can be looked up via container_of macro.
> 
> Everything else looks good.
> 
> With that and changing to the new tasklet API:
> Reviewed-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> 
>> +	struct intel_guc_ct *ct = (struct intel_guc_ct *)data;
>> +
>> +	ct_try_receive_message(ct);
>> +}
>> +
>>  /*
>>   * When we're communicating with the GuC over CT, GuC uses events
>>   * to notify us about new messages being posted on the RECV buffer.
>>   */
>>  void intel_guc_ct_event_handler(struct intel_guc_ct *ct)
>>  {
>> -	u32 msg[GUC_CT_MSG_LEN_MASK + 1]; /* one extra dw for the header */
>> -	unsigned long flags;
>> -	int err = 0;
>> -
>>  	if (unlikely(!ct->enabled)) {
>>  		WARN(1, "Unexpected GuC event received while CT disabled!\n");
>>  		return;
>>  	}
>>  
>> -	do {
>> -		spin_lock_irqsave(&ct->ctbs.recv.lock, flags);
>> -		err = ct_read(ct, msg);
>> -		spin_unlock_irqrestore(&ct->ctbs.recv.lock, flags);
>> -		if (err)
>> -			break;
>> -
>> -		if (ct_header_is_response(msg[0]))
>> -			err = ct_handle_response(ct, msg);
>> -		else
>> -			err = ct_handle_request(ct, msg);
>> -	} while (!err);
>> +	ct_try_receive_message(ct);
>>  }
>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> index bc52dc479a14..cb222f202301 100644
>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.h
>> @@ -6,6 +6,7 @@
>>  #ifndef _INTEL_GUC_CT_H_
>>  #define _INTEL_GUC_CT_H_
>>  
>> +#include <linux/interrupt.h>
>>  #include <linux/spinlock.h>
>>  #include <linux/workqueue.h>
>>  
>> @@ -55,6 +56,8 @@ struct intel_guc_ct {
>>  		struct intel_guc_ct_buffer recv;
>>  	} ctbs;
>>  
>> +	struct tasklet_struct receive_tasklet;
>> +
>>  	struct {
>>  		u32 last_fence; /* last fence used to send request */
>>  
>> -- 
>> 2.28.0
>>
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