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

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, May 23, 2018 at 3:52 PM, Qiang Yu <yuq825@gmail.com> wrote:
> On Wed, May 23, 2018 at 5:29 PM, Christian König
> <ckoenig.leichtzumerken@gmail.com> 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.
>
> 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.

All the drivers using ttm have something that looks like vram, or a
requirement to move buffers around. Afaiui that includes virtio drm
driver. From your description you don't have such a requirement, and
then doing what etnaviv has done would be a lot simpler. Everything
that's not related to buffer movement handling is also available
outside of ttm already.
-Daniel

> 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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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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