[PATCH] drm/amdkfd: Disable Packet Manager in non HWS mode except Hawaii

[Kuehling, Felix]

If you want to optimize driver init time, you should check what actually 
takes the most time. Randomly micro-optimizing things that may not even 
matter only increases complexity for no benefit.

Typically the things that make initialization slow are points where we 
synchronize with the GPU or random sleeps or delays to allow the 
hardware to complete something. A few lines of code that only run on the 
CPU will not make an appreciable difference.

Regards,
   Felix

On 2019-04-17 5:17 p.m., Zhao, Yong wrote:
> I can fix that cosmetic line. I did not measure the difference, but
> driver initialization usually takes a longer time, that's why I am
> trying to reduce it. Also, it means one less thing to worry about during
> non HWS mode bringup, because we don't need to deal with HIQ any more.
> With that, what do you think now?
>
> Regards,
>
> Yong
>
> On 2019-04-17 5:06 p.m., Kuehling, Felix wrote:
>> On 2019-04-17 4:54 p.m., Zhao, Yong wrote:
>>> The packet manager is only needed for HWS mode, as well as Hawaii in non
>>> HWS mode. So only initialize it under those scenarios. This is useful
>>> especially for emulation environment when things are slow.
>> I never thought of packet manager initialization as something expensive.
>> Why does this matter? In emulation, the GPU is slow, but the CPU should
>> be OK. Packet manager initialization doesn't do any waiting for the GPU,
>> so I don't see how this would have any measurable impact.
>>
>> Anyway, see one cosmetic comment inline.
>>
>>
>>> Change-Id: Iedfa07c94241e3252463e1e5ea537543c2ccef03
>>> Signed-off-by: Yong Zhao <Yong.Zhao at amd.com>
>>> ---
>>>     .../gpu/drm/amd/amdkfd/kfd_device_queue_manager.c   | 13 +++++++++++--
>>>     1 file changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
>>> index 1d6b15788ebf..ec83914d9867 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
>>> @@ -911,13 +911,22 @@ static void uninitialize(struct device_queue_manager *dqm)
>>>     
>>>     static int start_nocpsch(struct device_queue_manager *dqm)
>>>     {
>>> +	int ret = 0;
>> checkpatch.pl would complain that there should be an empty line after
>> variable declarations.
>>
>>
>>>     	init_interrupts(dqm);
>>> -	return pm_init(&dqm->packets, dqm);
>>> +	/* Cache flushing on Hawaii in non HWS mode is done through packet
>>> +	 * manager (PM), so we need to initialize PM for Hawaii.
>>> +	 */
>>> +	if (dqm->dev->device_info->asic_family == CHIP_HAWAII)
>>> +		ret = pm_init(&dqm->packets, dqm);
>>> +
>>> +	return ret;
>>>     }
>>>     
>>>     static int stop_nocpsch(struct device_queue_manager *dqm)
>>>     {
>>> -	pm_uninit(&dqm->packets);
>>> +	if (dqm->dev->device_info->asic_family == CHIP_HAWAII)
>>> +		pm_uninit(&dqm->packets);
>>> +
>>>     	return 0;
>>>     }
>>>     
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