Re: [EARLY RFC][PATCH] dma-buf: Add dma-buf heaps framework

["Andrew F. Davis" <afd@ti.com>]

On 2/26/19 5:40 PM, John Stultz wrote:
> On Tue, Feb 26, 2019 at 11:21 AM John Stultz <john.stultz@linaro.org> wrote:
>>
>> On Tue, Feb 26, 2019 at 6:47 AM Andrew F. Davis <afd@ti.com> wrote:
>>> On 2/26/19 12:20 AM, John Stultz wrote:
>>>> It boots w/ AOSP, and allocations seem to work, but there's something
>>>> wrong with the dmabuf mmaping which casues the homescreen to crash
>>>> over and over.
>>>> (userland patches updated here:
>>>> https://android-review.googlesource.com/c/device/linaro/hikey/+/909436)
>>>>
>>>
>>> Interesting, I wonder if the caching stuff is not right here, I'll see
>>> if I can get this working on my side (AOSP on Beagle x15).
>>>
>>
>> Let me know if you figure anything out, I'll also be looking at this today.
>>
> 
> Ok. Figured out the issue. There was a missing:
>   len = PAGE_ALIGN(len)
> assignment that the core used to do before calling the heap alloc op.
> 

Ah, that was my bad then, I dropped that line thinking the heaps should
take care of it, forcing allocation to the page length does make sense
though, we cant pass any less back to userspace.

> Adding that into the heap alloc op got it booting ok w/ AOSP.
> 
> I've updated the patches here:
> kernel: https://git.linaro.org/people/john.stultz/android-dev.git/log/?h=dev/dma-buf-heap
> userland: https://android-review.googlesource.com/c/device/linaro/hikey/+/909436
> 
> 
>> I also realized some of Benajmin's error path improvements are going
>> to be hard to fix w/ my current code, specifically having the allocate
>> op do the allocation of the dma_heap_buffer (since we don't have a
>> free op, if something fails creating the dmabuf fd in the core, we
>> don't have a hook to release the dma_heap_buffer and heap private
>> data).
> 

We can always add back the free op, the alternative is to have the heap
export the fd.

I'm not sure either is needed though, when we
dma_buf_put(buffer->dmabuf) on the error path it should trigger the
release op, and that can cleanup the allocations in the heap.

> I also realized doing my development and testing against my
> hikey960-mainline-WIP branch, I accidentally folded in an ion hack I
> was using to reduce cache operations, so I'll need to undo that in the
> heap-helpers.c.  But at least we have a rough validation point for the
> design.
> 

Great! The details of the heap-helpers can always get fixed up at a
later point, validation of the core working is really good to hear.

Thanks,
Andrew

> thanks
> -john
> 
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