• Rob Clark's avatar
    freedreno: import libdrm_freedreno + redesign submit · f3cc0d27
    Rob Clark authored
    In the pursuit of lowering driver overhead, it became clear that some
    amount of redesign of how libdrm_freedreno constructs the submit ioctl
    would be needed.  In particular, as the gallium driver is starting to
    make heavier use of CP_SET_DRAW_STATE state groups/objects, the over-
    head of tracking cmd buffers and relocs becomes too much.  And for
    "streaming" state, which isn't ever reused (like uniform uploads) the
    overhead of allocating/freeing ringbuffer[1] objects is too high.
    
    This redesign makes two main changes:
    
     1) Introduces a fd_submit object for tracking bos and cmds table
        for the submit ioctl, making ringbuffer objects more light-
        weight.  This was previously done in the ringbuffer.  But we
        have many ringbuffer instances involved in a submit (gmem +
        draw + potentially 1000's of state-group rbs), and only need
        a single bos and cmds table.  (Reloc table is still per-rb)
    
        The submit is also a convenient place for a slab allocator for
        ringbuffer objects.  Other options would have required locking
        because, while we can guarantee allocations will only happen on
        a single thread, free's could happen either on the application
        thread or the flush_queue thread.  With the slab allocator in
        the submit object, any frees that happen on the flush_queue
        thread happen after we know that the application thread is done
        with the submit.
    
     2) Introduce a new "softpin" msm_ringbuffer_sp implementation that
        does not use relocs and only has cmds table entries for IB1 (ie.
        the cmdstream buffers that kernel needs to CP_INDIRECT_BUFFER
        to from the RB).  To do this properly will require some updates
        on the kernel side, so whether you get the softpin or legacy
        submit/ringbuffer implementation at runtime depends on your
        kernel version.
    
    To make all these changes in libdrm would basically require adding a
    libdrm_freedreno2, so this is a good point to just pull the libdrm code
    into mesa.  Plus it allows for using mesa's hashtable, slab allocator,
    etc.  And it lets us have asserts enabled for debug mesa buids but
    omitted for release builds.  And it makes life easier if further API
    changes become necessary.
    
    At this point I haven't tried to pull in the kgsl backend.  Although
    I left the level of vfunc indirection which would make it possible
    to have other backends.  (And this was convenient to keep to allow
    for the "softpin" ringbuffer to coexist.)
    
    NOTE: if bisecting a build error takes you here, try a clean build.
    There are a bunch of ways things can go wrong if you still have
    libdrm_freedreno cflags.
    
    [1] "ringbuffer" is probably a bad name, the only level of cmdstream
        buffer that is actually a ring is RB managed by kernel.  User-
        space cmdstream is all IB1/IB2 and state-groups.
    Reviewed-by: default avatarKristian H. Kristensen <hoegsberg@chromium.org>
    Reviewed-by: default avatarEric Engestrom <eric.engestrom@intel.com>
    Signed-off-by: default avatarRob Clark <robdclark@gmail.com>
    f3cc0d27
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