[RFC] Host1x/TegraDRM UAPI

[Mikko Perttunen]

On 6/25/20 1:33 AM, Dmitry Osipenko wrote:
> 23.06.2020 15:09, Mikko Perttunen пишет:
>> struct drm_tegra_submit_relocation {
>>          /* [in] Index of GATHER or GATHER_UPTR command in commands. */
>>          __u32 gather_command_index;
>>
>>          /*
>>           * [in] Mapping handle (obtained through CHANNEL_MAP) of the memory
>>           *   the address of which will be patched in.
>>           */
>>          __u32 mapping_id;
>>
>>          /*
>>           * [in] Offset in the gather that will be patched.
>>           */
>>          __u64 gather_offset;
>>
>>          /*
>>           * [in] Offset in target buffer whose paddr/IOVA will be written
>>           *   to the gather.
>>           */
>>          __u64 target_offset;
>>
>>          /*
>>           * [in] Number of bits the resulting address will be logically
>>           *   shifted right before writing to gather.
>>           */
>>          __u32 shift;
>>
>>          __u32 reserved[1];
>> };
> 
> We will also need read/write direction flag here for the
> DMA-reservations set up, it will be used for the implicit BO fencing by
> the job's scheduler.
> 

Ideally on newer chips with context isolation, we no longer know what 
DMA-BUFs are being used by the job at submit time - they would just be 
pointers after being MAPped.

Do you know how other GPUs deal with DMA reservations - I expect 
separate MAP and SUBMIT steps would be pretty common? Do you have to 
pass the DMA-BUF to both steps (i.e. do IOMMU mapping during MAP, and 
manage reservations at SUBMIT)?

Mikko