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Enabling ION with CMA heap on imx6
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Carlos Rafael Giani
On i.MX6 machines, it is currently not possible to use the ION allocator. However, there is no hardware limitation that requires ION to be disabled.
If ION were enabled, with a CMA heap, then it would be possible for userspace to allocate DMA-BUF buffers. I could then enable the ion packageconfig in the libimxdmabuffer recipe. The defconfig only needs these additions: CONFIG_ION=y CONFIG_ION_SYSTEM_HEAP=y CONFIG_ION_CMA_HEAP=y I tried it out, worked fine. Using DMA-BUF for allocating physically contiguous memory (via CMA) is preferable over using other allocators (like the ones from the VPU, IPU etc.) since it allows for proper buffer sharing, ownership transfer, is based on FDs (though physical address are accessible via an NXP extension), and there are extensions in OpenCL, OpenGL etc. for importing DMA-BUF. V4L2 also has DMA-BUF support. Opinions?
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Otavio Salvador
Hello Carlos,
Em ter., 20 de out. de 2020 às 05:19, Carlos Rafael Giani via lists.yoctoproject.org <crg7475=mailbox.org@...> escreveu: On i.MX6 machines, it is currently not possible to use the IONPlease prepare the PR for it; also see if i.MX8 couldn't also benefit from it. -- Otavio Salvador O.S. Systems http://www.ossystems.com.br http://code.ossystems.com.br Mobile: +55 (53) 9 9981-7854 Mobile: +1 (347) 903-9750
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Andrey Zhizhikin
On Tue, Oct 20, 2020 at 10:19 AM Carlos Rafael Giani via
lists.yoctoproject.org <crg7475=mailbox.org@...> wrote: From the past experience I had with ION allocators in the past, I would try to refrain from using it. It is still residing in staging folder, which means that the API compatibility is not guaranteed. I had an experience where Application used ION in 4.4.y kernel, and should be re-written when 4.9.y kernel has been released due to significant changes in the ION UAPI. I would personally not recommend using it until it would be moved from staging to drivers. If one plans to base development on ION API - this should be taken into consideration. -- Regards, Andrey.
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Carlos Rafael Giani
For i.MX8 it is enabled already.
On 20.10.20 13:31, Otavio Salvador
wrote:
Hello Carlos, Em ter., 20 de out. de 2020 às 05:19, Carlos Rafael Giani via lists.yoctoproject.org <crg7475=mailbox.org@...> escreveu:On i.MX6 machines, it is currently not possible to use the ION allocator. However, there is no hardware limitation that requires ION to be disabled. If ION were enabled, with a CMA heap, then it would be possible for userspace to allocate DMA-BUF buffers. I could then enable the ion packageconfig in the libimxdmabuffer recipe. The defconfig only needs these additions: CONFIG_ION=y CONFIG_ION_SYSTEM_HEAP=y CONFIG_ION_CMA_HEAP=y I tried it out, worked fine. Using DMA-BUF for allocating physically contiguous memory (via CMA) is preferable over using other allocators (like the ones from the VPU, IPU etc.) since it allows for proper buffer sharing, ownership transfer, is based on FDs (though physical address are accessible via an NXP extension), and there are extensions in OpenCL, OpenGL etc. for importing DMA-BUF. V4L2 also has DMA-BUF support. Opinions?Please prepare the PR for it; also see if i.MX8 couldn't also benefit from it.
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Carlos Rafael Giani
Yes, this happened in the past. However, the benefits of DMA-BUF outweigh this IMO. I also have the libimxdmabuffer library to encapsulate such details.
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The alternative is to rely on IPU/VPU/etc. specific allocators, which come with more significant downsides.
On 20.10.20 13:38, Andrey Zhizhikin wrote:
On Tue, Oct 20, 2020 at 10:19 AM Carlos Rafael Giani via
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