Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence implementation for fences

["Christian König" <christian.koenig@amd.com>]

Hi Maarten,

try to implement this as a replacement for specifying the 
RADEON_FENCE_JIFFIES_TIMEOUT on wait_event_*. And reset the timeout 
every time radeon_fence_process is called and not only when any of the 
sequences increment.

I don't have the time right now to look deeper into it or help with the 
patch, but the general approach sounds valid to me.

Regards,
Christian.

Am 23.07.2014 16:05, schrieb Maarten Lankhorst:
> op 23-07-14 15:16, Maarten Lankhorst schreef:
>> op 23-07-14 14:36, Christian König schreef:
>>> Am 23.07.2014 12:52, schrieb Daniel Vetter:
>>>> On Wed, Jul 23, 2014 at 12:13 PM, Christian König
>>>> <christian.koenig@amd.com> wrote:
>>>>>> And the dma-buf would still have fences belonging to both drivers, and it
>>>>>> would still call from outside the driver.
>>>>> Calling from outside the driver is fine as long as the driver can do
>>>>> everything necessary to complete it's work and isn't forced into any ugly
>>>>> hacks and things that are not 100% reliable.
>>>>>
>>>>> So I don't see much other approach as integrating recovery code for not
>>>>> firing interrupts and some kind of lockup handling into the fence code as
>>>>> well.
>>>> That approach doesn't really work at that well since every driver has
>>>> it's own reset semantics. And we're trying to move away from global
>>>> reset to fine-grained reset. So stop-the-world reset is out of
>>>> fashion, at least for i915. As you said, reset is normal in gpus and
>>>> we're trying to make reset less invasive. I really don't see a point
>>>> in imposing a reset scheme upon all drivers and I think you have about
>>>> as much motivation to convert radeon to the scheme used by i915 as
>>>> I'll have for converting to the one used by radeon. If it would fit at
>>>> all.
>>> Oh my! No, I didn't wanted to suggest any global reset infrastructure.
>>>
>>> My idea was more that the fence framework provides a fence->process_signaling callback that is periodically called after enable_signaling is called to trigger manual signal processing in the driver.
>>>
>>> This would both be suitable as a fallback in case of not working interrupts as well as a chance for any driver to do necessary lockup handling.
>> I managed to do it without needing it to be part of the interface? I'm not sure whether radeon_fence_driver_recheck needs exclusive_lock, but if so it's a small change..
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
>> index 7fbfd41479f1..51b646b9c8bb 100644
>> --- a/drivers/gpu/drm/radeon/radeon.h
>> +++ b/drivers/gpu/drm/radeon/radeon.h
>> @@ -345,6 +345,9 @@ struct radeon_fence_driver {
>>   	uint64_t			sync_seq[RADEON_NUM_RINGS];
>>   	atomic64_t			last_seq;
>>   	bool				initialized;
>> +	struct delayed_work		work;
>> +	struct radeon_device *rdev;
>> +	unsigned ring;
>>   };
>>   
>>   struct radeon_fence_cb {
>> diff --git a/drivers/gpu/drm/radeon/radeon_fence.c b/drivers/gpu/drm/radeon/radeon_fence.c
>> index da83f36dd708..955c825946ad 100644
>> --- a/drivers/gpu/drm/radeon/radeon_fence.c
>> +++ b/drivers/gpu/drm/radeon/radeon_fence.c
>> @@ -231,6 +231,9 @@ static bool __radeon_fence_process(struct radeon_device *rdev, int ring)
>>   		}
>>   	} while (atomic64_xchg(&rdev->fence_drv[ring].last_seq, seq) > seq);
>>   
>> +	if (!wake && last_seq < last_emitted)
>> +		schedule_delayed_work(&rdev->fence_drv[ring].work, jiffies_to_msecs(10));
>> +
>>
> When trying this: if (seq < last_emitted) is probably a better check.
>
> ~Maarten
>