[PATCH] drm/amdgpu: defer test IBs on the rings at boot

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Am 13.04.2018 um 09:01 schrieb S, Shirish:
>
>
> On 4/13/2018 11:53 AM, Christian König wrote:
>> Am 13.04.2018 um 06:07 schrieb Shirish S:
>>> amdgpu_ib_ring_tests() runs test IB's on rings at boot
>>> contributes to ~500 ms of amdgpu driver's boot time.
>>>
>>> This patch defers it and adds a check to report
>>> in amdgpu_info_ioctl() if it was scheduled or not.
>>
>> That is rather suboptimal, but see below.
>>
> Which part is sub-optimal, deferring or checking if the work is 
> scheduled?

That was about the check. We should wait for the test to finish instead 
of printing an error and continuing.

>>>
>>> Signed-off-by: Shirish S <shirish.s at amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  2 ++
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 20 +++++++++++++++++---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c    |  3 +++
>>>   3 files changed, 22 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> index 5734871..ae8f722 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>> @@ -1611,6 +1611,8 @@ struct amdgpu_device {
>>>         /* delayed work_func for deferring clockgating during resume */
>>>       struct delayed_work     late_init_work;
>>> +    /* delayed work_func to defer testing IB's on rings during boot */
>>> +    struct delayed_work     late_init_test_ib_work;
>>
>> You must put the IB test into the late_init_work as well, otherwise 
>> the two delayed workers can race with each other.
>>
> I thought  from the comment above the declaration, its clear why i am 
> creating 2 work structures.
> late_init_work is to optimize resume time and late_init_test_ib_work 
> is to optimize the boot time.
> There cant be race as the context in which they are called are totally 
> different.

Late init enables power and clock gating. If I'm not completely mistaken 
we don't do the power/clock gating earlier because we had to wait for 
the IB test to finish.

Could be that modern ASICs have additional logic to prevent that, but 
the last time I worked on this power gating a block while you run 
something on it could even crash the whole system.

>>>         struct amdgpu_virt    virt;
>>>       /* firmware VRAM reservation */
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> index 1762eb4..e65a5e6 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> @@ -63,6 +63,7 @@ MODULE_FIRMWARE("amdgpu/vega12_gpu_info.bin");
>>>   MODULE_FIRMWARE("amdgpu/raven_gpu_info.bin");
>>>     #define AMDGPU_RESUME_MS        2000
>>> +#define AMDGPU_IB_TEST_SCHED_MS        2000
>>>     static const char *amdgpu_asic_name[] = {
>>>       "TAHITI",
>>> @@ -2105,6 +2106,16 @@ bool amdgpu_device_asic_has_dc_support(enum 
>>> amd_asic_type asic_type)
>>>       }
>>>   }
>>>   +static void amdgpu_device_late_init_test_ib_func_handler(struct 
>>> work_struct *work)
>>> +{
>>> +    struct amdgpu_device *adev =
>>> +        container_of(work, struct amdgpu_device, 
>>> late_init_test_ib_work.work);
>>> +    int r = amdgpu_ib_ring_tests(adev);
>>> +
>>> +    if (r)
>>> +        DRM_ERROR("ib ring test failed (%d).\n", r);
>>> +}
>>> +
>>>   /**
>>>    * amdgpu_device_has_dc_support - check if dc is supported
>>>    *
>>> @@ -2212,6 +2223,8 @@ int amdgpu_device_init(struct amdgpu_device 
>>> *adev,
>>>       INIT_LIST_HEAD(&adev->ring_lru_list);
>>>       spin_lock_init(&adev->ring_lru_list_lock);
>>>   +    INIT_DELAYED_WORK(&adev->late_init_test_ib_work,
>>> +              amdgpu_device_late_init_test_ib_func_handler);
>>>       INIT_DELAYED_WORK(&adev->late_init_work,
>>>                 amdgpu_device_ip_late_init_func_handler);
>>>   @@ -2374,9 +2387,9 @@ int amdgpu_device_init(struct amdgpu_device 
>>> *adev,
>>>           goto failed;
>>>       }
>>>   -    r = amdgpu_ib_ring_tests(adev);
>>> -    if (r)
>>> -        DRM_ERROR("ib ring test failed (%d).\n", r);
>>> +    /* Schedule amdgpu_ib_ring_tests() */
>>> +    mod_delayed_work(system_wq, &adev->late_init_test_ib_work,
>>> +            msecs_to_jiffies(AMDGPU_IB_TEST_SCHED_MS));
>>
>> That doesn't work like you intended. mod_delayed_work() overrides the 
>> existing handler.
>>
>> What you wanted to use is queue_delayed_work(), but as I said we 
>> should only have one delayed worker.
> mod_delayed_work() is safer and optimal method that replaces 
> cancel_delayed_work() followed by queue_delayed_work().
> (https://lkml.org/lkml/2011/2/3/175)
> But if you strongly insist i don't mind changing it.

Well, mod_delayed_work() does NOT replace queue_delayed_work(). Those 
two functions are for different use cases.

The link you posted actually explains it quite well:
> So, cancel_delayed_work() followed by queue_delayed_work() schedules
> the work to be executed at the specified time regardless of the
> current pending state while queue_delayed_work() takes effect iff
> currently the work item is not pending.

queue_delayed_work() takes only effect if the work item is not already 
pending/executing.

In other words with queue_delayed_work() you don't risk executing things 
twice when the work is already executing.

While with mod_delayed_work() you absolutely make sure to execute things 
twice when it is already running.

If I'm not completely mistaken it should not matter in this case, but 
queue_delayed_work() is used more commonly I think.

>>
>>>         if (amdgpu_sriov_vf(adev))
>>>           amdgpu_virt_init_data_exchange(adev);
>>> @@ -2469,6 +2482,7 @@ void amdgpu_device_fini(struct amdgpu_device 
>>> *adev)
>>>       }
>>>       adev->accel_working = false;
>>>       cancel_delayed_work_sync(&adev->late_init_work);
>>> + cancel_delayed_work_sync(&adev->late_init_test_ib_work);
>>>       /* free i2c buses */
>>>       if (!amdgpu_device_has_dc_support(adev))
>>>           amdgpu_i2c_fini(adev);
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> index 487d39e..057bd9a 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
>>> @@ -279,6 +279,9 @@ static int amdgpu_info_ioctl(struct drm_device 
>>> *dev, void *data, struct drm_file
>>>       if (!info->return_size || !info->return_pointer)
>>>           return -EINVAL;
>>>   +    if (delayed_work_pending(&adev->late_init_test_ib_work))
>>> +        DRM_ERROR("IB test on ring not executed\n");
>>> +
>>
>> Please use flush_delayed_work() instead of issuing and error here.
>>
> Agree, wasn't sure of what to do here :).
> So i will re-spin with the flush part added. Hope this reply clarifies 
> your comments.
> Thanks.
> Regards,
> Shirish S
>> Regards,
>> Christian.
>>
>>>       switch (info->query) {
>>>       case AMDGPU_INFO_ACCEL_WORKING:
>>>           ui32 = adev->accel_working;
>>
>



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