How to share texture memory between CPU/GPU for firefly's/rk3288 fbdev Mali-T764

Hi, I have the same issue, with slightly different parameters: I'm running Android 4.4.4 on my Firefly and wish to render ultra high resolution video (3840 x 2160) at 60 fps. Any sort of copy would make this unfeasible.

Based on research on the net and these forums, it seems this task can be accomplished with zero copy by directly accessing the physical pointer to the texture memory via UMP or DMABUF. Is there documentation on how to go about achieving this?

EDIT: Seems I can answer my own question as Android implementation of GraphicsBuffer provides this.

Using direct textures on Android

Using GL_OES_EGL_image_external on Android

Hi mac_l1,

You are right: on Android you would use a GraphicBuffer:

android::sp<android::GraphicBuffer> pGraphicBuffer = new android::GraphicBuffer(width,height, ...);
eglImage = eglCreateImageKHR(eglDisplay, EGL_NO_CONTEXT, EGL_NATIVE_BUFFER_ANDROID, (EGLClientBuffer)pGraBuf->getNativeBuffer(), NULL);

For FBdev. because it's not a full window system things are a bit more hacky, you need to define a secret structure and use some secret color formats (Let me know which one you need and I'll give you the magic value):

/* This is a magic value expected by the driver: let me know if you need a different format */
#define YUYV_FORMAT  0x001022A88LL


struct fbdev_pixmap
{
  int width, height;


  struct
  {
  /** @brief The line stride of each plane.
  * For each plane required by the format, the number of bytes from one line of samples to the next. Other entries in
  * the array should be 0.
  */
  khronos_usize_t stride;
  /** @brief The byte size of each plane.
  * For each plane required by the format, the number of bytes taken up by that plane. That includes any space wasted
  * in partially-used blocks.
  */
  khronos_usize_t size;
  /** @brief The offset from the memory handle to each plane.
  * For each plane required by the format, the number of bytes from the start of the allocation to the start of that
  * plane. Other entries in the array should be 0.
  */
  khronos_usize_t offset;
  }
  planes[3];


  /** An integer that specifies the format of the pixmap. Its meaning is known by the Mali driver. */
  uint64_t pixmap_format;
  /* dma_buf fd for each of the plan */
  int handles[3];
};

struct fbdev_pixmap pixmap;
memset(&pixmap, 0, sizeof(struct fbdev_pixmap));
pixmap.width = width;
pixmap.height = height;
pixmap.handles[0] = dma_fd;
pixmap.planes[0].stride = width * pixel_size;
pixmap.planes[0].size = width * height * pixel_size;
pixmap.pixmap_format = YUYV_FORMAT;


_egl_img  = eglCreateImageKHR(_egl_display, EGL_NO_CONTEXT, EGL_NATIVE_PIXMAP_KHR, (EGLNativePixmapType) &pixmap, NULL));

https://bitbucket.org/T-Firefly/firefly-rk3288-kernel/src/f4d954d67f9e5689f1ddbbbd3050a8041424dd48/drivers/video/rockchip/rk_fb.c?at=master#cl-2469

T-Firefly / Firefly-RK3288-kernel / source / include / linux / rk_fb.h — Bitbucket

However the issue is that the fbdev Mali-T76x user-side binary driver available from malideveloper.arm.com is not specific to this kernel, or not even to Firefly but to any system with a Mali-T76x GPU.  So it doesn't know about this ioctl.  It would need to call it to get a DMA-BUF file descriptor from the display driver and then pass it to the kernel-side driver.

We're planning to fix support for DMA-BUF in fbdev in future drivers with a portable kernel patch, but unfortunately I can't yet tell when this will be available as we rely on other things to be released first.

Then to import a DMA-BUF file descriptor from the video decoder into the GPU, there is an extension for that:

https://www.khronos.org/registry/egl/extensions/EXT/EGL_EXT_image_dma_buf_import.txt

It is not yet enabled in our r5p0 driver but should be in a future version.  I'll post another message when this is released.

For the rk3288 video decoder I can obtain the filedescriptor by using rockchips VPUMemGetFD() provided by their vpu memory allocator code: T-Firefly / Firefly-RK3288   / source  / frameworks / av / media / libstagefright / libvpu / common / vpu_mem_dmabuf.c —… Using libhybris I can access this android library - libvpu.

As dma-buf import is not yet supported in r5p0 driver I guess, for now, will have to use your android mali driver with libhybris - far from ideal.

I am of course very interested in your future release!

PS: for those interested, also found some interesting links related to dma_buf / ion stuff:

DMA buffer sharing in 3.3 [LWN.net]

The Android ION memory allocator [LWN.net]

Daeseok's Blog :: [ION] Sharing a buffer between kernel-space and user-space

ION Buffer sharing mechanism | :(){ :|:& };: