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

[Zhao, Yong]

Okay, I will abandon it.

Yong

On 2019-04-17 5:44 p.m., Kuehling, Felix wrote:
> 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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