• Daniel Vetter's avatar
    drm/vblank: drop the mode argument from drm_calc_vbltimestamp_from_scanoutpos · 1bf6ad62
    Daniel Vetter authored
    If we restrict this helper to only kms drivers (which is the case) we
    can look up the correct mode easily ourselves. But it's a bit tricky:
    
    - All legacy drivers look at crtc->hwmode. But that is updated already
      at the beginning of the modeset helper, which means when we disable
      a pipe. Hence the final timestamps might be a bit off. But since
      this is an existing bug I'm not going to change it, but just try to
      be bug-for-bug compatible with the current code. This only applies
      to radeon&amdgpu.
    
    - i915 tries to get it perfect by updating crtc->hwmode when the pipe
      is off (i.e. vblank->enabled = false).
    
    - All other atomic drivers look at crtc->state->adjusted_mode. Those
      that look at state->requested_mode simply don't adjust their mode,
      so it's the same. That has two problems: Accessing crtc->state from
      interrupt handling code is unsafe, and it's updated before we shut
      down the pipe. For nonblocking modesets it's even worse.
    
    For atomic drivers try to implement what i915 does. To do that we add
    a new hwmode field to the vblank structure, and update it from
    drm_calc_timestamping_constants(). For atomic drivers that's called
    from the right spot by the helper library already, so all fine. But
    for safety let's enforce that.
    
    For legacy driver this function is only called at the end (oh the
    fun), which is broken, so again let's not bother and just stay
    bug-for-bug compatible.
    
    The  benefit is that we can use drm_calc_vbltimestamp_from_scanoutpos
    directly to implement ->get_vblank_timestamp in every driver, deleting
    a lot of code.
    
    v2: Completely new approach, trying to mimick the i915 solution.
    
    v3: Fixup kerneldoc.
    
    v4: Drop the WARN_ON to check that the vblank is off, atomic helpers
    currently unconditionally call this. Recomputing the same stuff should
    be harmless.
    
    v5: Fix typos and move misplaced hunks to the right patches (Neil).
    
    v6: Undo hunk movement (kbuild).
    
    Cc: Mario Kleiner <mario.kleiner@tuebingen.mpg.de>
    Cc: Eric Anholt <eric@anholt.net>
    Cc: Rob Clark <robdclark@gmail.com>
    Cc: linux-arm-msm@vger.kernel.org
    Cc: freedreno@lists.freedesktop.org
    Cc: Alex Deucher <alexander.deucher@amd.com>
    Cc: Christian König <christian.koenig@amd.com>
    Cc: Ben Skeggs <bskeggs@redhat.com>
    Reviewed-by: default avatarNeil Armstrong <narmstrong@baylibre.com>
    Acked-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
    Signed-off-by: default avatarDaniel Vetter <daniel.vetter@intel.com>
    Link: http://patchwork.freedesktop.org/patch/msgid/20170509140329.24114-4-daniel.vetter@ffwll.ch
    1bf6ad62
amdgpu_kms.c 32.7 KB