• Chris Wilson's avatar
    drm/i915: Suppress spurious vblank interrupts · 78c6e170
    Chris Wilson authored
    Hugh Dickins found that characters in xterm were going missing and oft
    delayed. Being the curious type, he managed to associate this with the
    new high-precision vblank patches; disabling these he found, restored
    the orderliness of his characters.
    
    The oddness begins when one realised that Hugh was not using vblanks at
    all on his system (fvwm and some xterms). Instead, all he had to go on
    were warning of a pipe underrun, curiously enough at around 60Hz. He
    poked and found that in addition to the underrun warning, the hardware
    was flagging the start of a new frame, a vblank, which in turn was
    kicking off the pending vblank processing code.
    
    There is little we can do for the underruns on Hugh's machine, a
    Crestline [965GM], which must have its FIFO watermarks set to 8.
    However, we do not need to process the vblank if we know that they are
    disabled...
    Reported-by: default avatarHugh Dickins <hughd@google.com>
    Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
    78c6e170
drm_irq.c 38.8 KB