Re: [RFC,libdrm 1/3] tegra: Add stream library

[Mark Zhang <nvmarkzhang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 12/28/2012 03:45 PM, Arto Merilainen wrote:
> On 12/28/2012 08:47 AM, Mark Zhang wrote:
>>> +int tegra_fence_is_valid(const struct tegra_fence *fence)
>>> +{
>>> +    int valid = fence ? 1 : 0;
>>> +    valid = valid && fence->id != (uint32_t) -1;
>>> +    valid = valid && fence->id < 32;
>>
>> Hardcode here. Assume always has 32 syncpts.
>> Change to a micro wrapped with tegra version ifdef will be better.
>>
> 
> You are correct. I will fix this.
> 
>>> +    return valid;
>>> +}
>>> +
>> [...]
>>> +
>>> +    /* Add fences */
>>> +    if (num_fences) {
>>> +
>>> +        tegra_stream_push(stream,
>>> +            nvhost_opcode_setclass(NV_HOST1X_CLASS_ID,
>>> +            host1x_uclass_wait_syncpt_r(), num_fences));
>>> +
>>> +        for (; num_fences; num_fences--, fence++) {
>>> +            assert(tegra_fence_is_valid(fence));
>>
>> This is useless. We already add "1 + num_fences" to num_words above. So
>> move this "assert" before adding "1 + num_fences" to num_words makes
>> sense.
>>
> 
> The assertion checks the validity of a single fence - not if there is
> room in the command buffer.
> 
> The goal is to prevent having invalid fences in the command stream. If
> this check were not here it would be possible to initialise a fence with
> tegra_fence_clear() and put that fence into the stream.

My idea is, if one fence is invalid, then we should not count this in
"num_words". In current code, if one fence is invalid, then this fence
will not be pushed into the command stream, and the "num_words" shows a
wrong command buffer size.

So I think we should:
- validate the fences, remove the invalid fence
- update num_words
- then you don't need to check fence here - I mean, before push a host1x
syncpt wait command into the active buffer of stream.

> 
>>> +
>>> +            tegra_stream_push(stream,
>>> nvhost_class_host_wait_syncpt(fence->id,
>>> +                fence->value));
>>> +        }
>>> +    }
>>> +
>>> +    if (class_id)
>>> +        tegra_stream_push(stream, nvhost_opcode_setclass(class_id,
>>> 0, 0));
>>> +
>>> +    return 0;
>>> +}
>>> +
>> [...]
>>> +
>>> +#endif /* TEGRA_DRMIF_H */
>>>
> 
> - Arto