[Freedreno] [PATCH 10/13] drm/msm: Support multiple ringbuffers

[Rob Clark]

On Thu, May 25, 2017 at 1:25 PM, Jordan Crouse <jcrouse at codeaurora.org> wrote:
> On Mon, May 08, 2017 at 02:35:06PM -0600, Jordan Crouse wrote:
>> -#define rbmemptr(adreno_gpu, member)  \
>> +#define _sizeof(member) \
>> +     sizeof(((struct adreno_rbmemptrs *) 0)->member[0])
>> +
>> +#define _base(adreno_gpu, member)  \
>>       ((adreno_gpu)->memptrs_iova + offsetof(struct adreno_rbmemptrs, member))
>>
>> +#define rbmemptr(adreno_gpu, index, member) \
>> +     (_base((adreno_gpu), member) + ((index) * _sizeof(member)))
>> +
>>  struct adreno_rbmemptrs {
>> -     volatile uint32_t rptr;
>> -     volatile uint32_t fence;
>> +     volatile uint32_t rptr[MSM_GPU_MAX_RINGS];
>> +     volatile uint32_t fence[MSM_GPU_MAX_RINGS];
>>  };
>
> I'm looking for opinions on moving this to a per-ring buffer object. It would be
> a lot simpler to understand but it would cost us a page per ring as opposed
> to the 1 page we use now.

Well, I guess sub-allocation is an option.. we don't *have* to do a
page-per memptrs struct just to have separate struct per pring.

Just turn the single rbmemptrs allocation into an memptrs[MAX_RINGS]..

BR,
-R

> Looking ahead we are going to want to start using trace messages in conjunction
> with tools like systrace:
>
> (https://developer.android.com/studio/profile/systrace-commandline.html)
>
> This will involve tracking the always on counter value at start/retire for each
> outstanding submit on each ring. I *think* we could fit those values into the
> existing rmemptrs buffer if we wanted to but I can't imagine these would be the
> last runtime statistics we would gather.
>
> I guess I'm leaning toward the per-ring solution but I'll listen to anybody
> argue that the memory usage isn't worth it.
>
> Jordan
>
> --
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