Re: [PATCH RFC 00/24] Lima DRM driver

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Am 23.05.2018 um 15:52 schrieb Qiang Yu:
On Wed, May 23, 2018 at 5:29 PM, Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:
Am 18.05.2018 um 11:27 schrieb Qiang Yu:
Kernel DRM driver for ARM Mali 400/450 GPUs.

This implementation mainly take amdgpu DRM driver as reference.

- Mali 4xx GPUs have two kinds of processors GP and PP. GP is for
    OpenGL vertex shader processing and PP is for fragment shader
    processing. Each processor has its own MMU so prcessors work in
    virtual address space.
- There's only one GP but multiple PP (max 4 for mali 400 and 8
    for mali 450) in the same mali 4xx GPU. All PPs are grouped
    togather to handle a single fragment shader task divided by
    FB output tiled pixels. Mali 400 user space driver is
    responsible for assign target tiled pixels to each PP, but mali
    450 has a HW module called DLBU to dynamically balance each
    PP's load.
- User space driver allocate buffer object and map into GPU
    virtual address space, upload command stream and draw data with
    CPU mmap of the buffer object, then submit task to GP/PP with
    a register frame indicating where is the command stream and misc
    settings.
- There's no command stream validation/relocation due to each user
    process has its own GPU virtual address space. GP/PP's MMU switch
    virtual address space before running two tasks from different
    user process. Error or evil user space code just get MMU fault
    or GP/PP error IRQ, then the HW/SW will be recovered.
- Use TTM as MM. TTM_PL_TT type memory is used as the content of
    lima buffer object which is allocated from TTM page pool. all
    lima buffer object gets pinned with TTM_PL_FLAG_NO_EVICT when
    allocation, so there's no buffer eviction and swap for now. We
    need reverse engineering to see if and how GP/PP support MMU
    fault recovery (continue execution). Otherwise we have to
    pin/unpin each envolved buffer when task creation/deletion.

Well pinning all memory is usually a no-go for upstreaming. But since you
are already using the drm_sched for GPU task scheduling why are you actually
needing this?

The scheduler should take care of signaling all fences when the hardware is
done with it's magic and that is enough for TTM to note that a buffer object
is movable again (e.g. unpin them).
Please correct me if I'm wrong.

Well, you are wrong :)

One way to implement eviction/swap is like this:
call validation on each buffers involved in a task, but this won't
prevent it from
eviction/swap when executing, so a GPU MMU fault may happen and in the
handler we need to recover the buffer evicted/swapped.

Another way is pin/unpin buffers evolved when task create/free.

First way is better when memory load is low and second way is better when
memory load is high. First way also need less memory.

So I'd prefer first way but due to the GPU MMU fault
HW op need reverse engineering, I have to pin all buffers now. After
the HW op is clear, I can choose one way to implement.

The general approach is:
1.) Lock all BOs
2.) Validate all BOs
3.) Add the fence
4.) Unlock the BOs

BOs can't be evicted while they are locked and since you already add the fence that should be perfectly sufficient to prevent it from being evicted until your operation is completed.

Using the MMU is certainly be better in general, but usually only optional and a pain in the ass to get working. We have that in amdgpu for quite a while as well now and still don't use it because of that.

Regards,
Christian.


Regards,
Qiang

Christian.


- Use drm_sched for GPU task schedule. Each OpenGL context should
    have a lima context object in the kernel to distinguish tasks
    from different user. drm_sched gets task from each lima context
    in a fair way.

Not implemented:
- Dump buffer support
- Power management
- Performance counter

This patch serial just pack a pair of .c/.h files in each patch.
For whole history of this driver's development, see:
https://github.com/yuq/linux-lima/commits/lima-4.17-rc4

Mesa driver is still in development and not ready for daily usage,
but can run some simple tests like kmscube and glamrk2, see:
https://github.com/yuq/mesa-lima

Andrei Paulau (1):
    arm64/dts: add switch-delay for meson mali

Lima Project Developers (10):
    drm/lima: add mali 4xx GPU hardware regs
    drm/lima: add lima core driver
    drm/lima: add GPU device functions
    drm/lima: add PMU related functions
    drm/lima: add PP related functions
    drm/lima: add MMU related functions
    drm/lima: add GPU virtual memory space handing
    drm/lima: add GEM related functions
    drm/lima: add GEM Prime related functions
    drm/lima: add makefile and kconfig

Qiang Yu (12):
    dt-bindings: add switch-delay property for mali-utgard
    arm64/dts: add switch-delay for meson mali
    Revert "drm: Nerf the preclose callback for modern drivers"
    drm/lima: add lima uapi header
    drm/lima: add L2 cache functions
    drm/lima: add GP related functions
    drm/lima: add BCAST related function
    drm/lima: add DLBU related functions
    drm/lima: add TTM subsystem functions
    drm/lima: add buffer object functions
    drm/lima: add GPU schedule using DRM_SCHED
    drm/lima: add context related functions

Simon Shields (1):
    ARM: dts: add gpu node to exynos4

   .../bindings/gpu/arm,mali-utgard.txt          |   4 +
   arch/arm/boot/dts/exynos4.dtsi                |  33 ++
   arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi   |   1 +
   .../boot/dts/amlogic/meson-gxl-mali.dtsi      |   1 +
   drivers/gpu/drm/Kconfig                       |   2 +
   drivers/gpu/drm/Makefile                      |   1 +
   drivers/gpu/drm/drm_file.c                    |   8 +-
   drivers/gpu/drm/lima/Kconfig                  |   9 +
   drivers/gpu/drm/lima/Makefile                 |  19 +
   drivers/gpu/drm/lima/lima_bcast.c             |  65 +++
   drivers/gpu/drm/lima/lima_bcast.h             |  34 ++
   drivers/gpu/drm/lima/lima_ctx.c               | 143 +++++
   drivers/gpu/drm/lima/lima_ctx.h               |  51 ++
   drivers/gpu/drm/lima/lima_device.c            | 407 ++++++++++++++
   drivers/gpu/drm/lima/lima_device.h            | 136 +++++
   drivers/gpu/drm/lima/lima_dlbu.c              |  75 +++
   drivers/gpu/drm/lima/lima_dlbu.h              |  37 ++
   drivers/gpu/drm/lima/lima_drv.c               | 466 ++++++++++++++++
   drivers/gpu/drm/lima/lima_drv.h               |  77 +++
   drivers/gpu/drm/lima/lima_gem.c               | 459 ++++++++++++++++
   drivers/gpu/drm/lima/lima_gem.h               |  41 ++
   drivers/gpu/drm/lima/lima_gem_prime.c         |  66 +++
   drivers/gpu/drm/lima/lima_gem_prime.h         |  31 ++
   drivers/gpu/drm/lima/lima_gp.c                | 293 +++++++++++
   drivers/gpu/drm/lima/lima_gp.h                |  34 ++
   drivers/gpu/drm/lima/lima_l2_cache.c          |  98 ++++
   drivers/gpu/drm/lima/lima_l2_cache.h          |  32 ++
   drivers/gpu/drm/lima/lima_mmu.c               | 154 ++++++
   drivers/gpu/drm/lima/lima_mmu.h               |  34 ++
   drivers/gpu/drm/lima/lima_object.c            | 120 +++++
   drivers/gpu/drm/lima/lima_object.h            |  87 +++
   drivers/gpu/drm/lima/lima_pmu.c               |  85 +++
   drivers/gpu/drm/lima/lima_pmu.h               |  30 ++
   drivers/gpu/drm/lima/lima_pp.c                | 418 +++++++++++++++
   drivers/gpu/drm/lima/lima_pp.h                |  37 ++
   drivers/gpu/drm/lima/lima_regs.h              | 304 +++++++++++
   drivers/gpu/drm/lima/lima_sched.c             | 497 ++++++++++++++++++
   drivers/gpu/drm/lima/lima_sched.h             | 126 +++++
   drivers/gpu/drm/lima/lima_ttm.c               | 409 ++++++++++++++
   drivers/gpu/drm/lima/lima_ttm.h               |  44 ++
   drivers/gpu/drm/lima/lima_vm.c                | 312 +++++++++++
   drivers/gpu/drm/lima/lima_vm.h                |  73 +++
   include/drm/drm_drv.h                         |  23 +-
   include/uapi/drm/lima_drm.h                   | 195 +++++++
   44 files changed, 5565 insertions(+), 6 deletions(-)
   create mode 100644 drivers/gpu/drm/lima/Kconfig
   create mode 100644 drivers/gpu/drm/lima/Makefile
   create mode 100644 drivers/gpu/drm/lima/lima_bcast.c
   create mode 100644 drivers/gpu/drm/lima/lima_bcast.h
   create mode 100644 drivers/gpu/drm/lima/lima_ctx.c
   create mode 100644 drivers/gpu/drm/lima/lima_ctx.h
   create mode 100644 drivers/gpu/drm/lima/lima_device.c
   create mode 100644 drivers/gpu/drm/lima/lima_device.h
   create mode 100644 drivers/gpu/drm/lima/lima_dlbu.c
   create mode 100644 drivers/gpu/drm/lima/lima_dlbu.h
   create mode 100644 drivers/gpu/drm/lima/lima_drv.c
   create mode 100644 drivers/gpu/drm/lima/lima_drv.h
   create mode 100644 drivers/gpu/drm/lima/lima_gem.c
   create mode 100644 drivers/gpu/drm/lima/lima_gem.h
   create mode 100644 drivers/gpu/drm/lima/lima_gem_prime.c
   create mode 100644 drivers/gpu/drm/lima/lima_gem_prime.h
   create mode 100644 drivers/gpu/drm/lima/lima_gp.c
   create mode 100644 drivers/gpu/drm/lima/lima_gp.h
   create mode 100644 drivers/gpu/drm/lima/lima_l2_cache.c
   create mode 100644 drivers/gpu/drm/lima/lima_l2_cache.h
   create mode 100644 drivers/gpu/drm/lima/lima_mmu.c
   create mode 100644 drivers/gpu/drm/lima/lima_mmu.h
   create mode 100644 drivers/gpu/drm/lima/lima_object.c
   create mode 100644 drivers/gpu/drm/lima/lima_object.h
   create mode 100644 drivers/gpu/drm/lima/lima_pmu.c
   create mode 100644 drivers/gpu/drm/lima/lima_pmu.h
   create mode 100644 drivers/gpu/drm/lima/lima_pp.c
   create mode 100644 drivers/gpu/drm/lima/lima_pp.h
   create mode 100644 drivers/gpu/drm/lima/lima_regs.h
   create mode 100644 drivers/gpu/drm/lima/lima_sched.c
   create mode 100644 drivers/gpu/drm/lima/lima_sched.h
   create mode 100644 drivers/gpu/drm/lima/lima_ttm.c
   create mode 100644 drivers/gpu/drm/lima/lima_ttm.h
   create mode 100644 drivers/gpu/drm/lima/lima_vm.c
   create mode 100644 drivers/gpu/drm/lima/lima_vm.h
   create mode 100644 include/uapi/drm/lima_drm.h


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