[PATCH v5 10/10] drm/amdgpu: add delay after userqueue mapping

[Shashank Sharma]

On 06/07/2023 19:41, Alex Deucher wrote:
> On Thu, Jul 6, 2023 at 8:36 AM Shashank Sharma <shashank.sharma at amd.com> wrote:
>> It has been observed that the MES FW needs 250-300us to map the gfx
>> userqueue, and if the user rings the doorbell before this duration,
>> the FW never recognizes the work. This patch adds the delay of 300
>> us after the queue mapping.
>>
>> V1: Moved the delay from userspace IOCTL to kernel (Alex).
>>
>> Cc: Alex Deucher <alexander.deucher at amd.com>
>> Cc: Christian Koenig <christian.koenig at amd.com>
>> Signed-off-by: Shashank Sharma <shashank.sharma at amd.com>
>> Signed-off-by: Arvind Yadav <arvind.yadav at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
>> index 8edb020683a1..78b58c5d0fd8 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v11_0.c
>> @@ -25,6 +25,7 @@
>>   #include <linux/firmware.h>
>>   #include <linux/module.h>
>>   #include <linux/pci.h>
>> +#include <linux/delay.h>
>>   #include "amdgpu.h"
>>   #include "amdgpu_gfx.h"
>>   #include "amdgpu_psp.h"
>> @@ -6749,6 +6750,12 @@ static int gfx_v11_0_userq_mqd_create(struct amdgpu_userq_mgr *uq_mgr,
>>                  goto free_ctx;
>>          }
>>
>> +       /*
>> +        * It has been observed that HWS needs appx 250-300us to map the queue, and the
>> +        * user needs to wait this duration before ringing the doorbell, or else the FW
>> +        * will never recognize the work.
>> +        */
>> +       udelay(300);
> Is there a way we can query the MES to verify that the queue is mapped
> and ready?  We should talk to the MES team.  This is hacky and may
> fail if the MES is busy, etc.

So far I have not received any input on this, I can restart a discussion.

- Shashank

> Alex
>
>
>>          return 0;
>>
>>   free_ctx:
>> --
>> 2.40.1
>>