• Stanislav Lisovskiy's avatar
    drm/i915: Implement PSF GV point support · 192fbfb7
    Stanislav Lisovskiy authored
    PSF GV points are an additional factor that can limit the
    bandwidth available to display, separate from the traditional
    QGV points.  Whereas traditional QGV points represent possible
    memory clock frequencies, PSF GV points reflect possible
    frequencies of the memory fabric.
    
    Switching between PSF GV points has the advantage of incurring
    almost no memory access block time and thus does not need to be
    accounted for in watermark calculations.
    
    This patch adds support for those on top of regular QGV points.
    Those are supposed to be used simultaneously, i.e we are always
    at some QGV and some PSF GV point, based on the current video
    mode requirements.
    Bspec: 64631, 53998
    
    v2: Seems that initial assumption made during ml conversation
        was wrong, PCode rejects any masks containing points beyond
        the ones returned, so even though BSpec says we have around
        8 points theoretically, we can mask/unmask only those which
        are returned, trying to manipulate those beyond causes a
        failure from PCode. So switched back to generating mask
        from 1 - num_qgv_points, where num_qgv_points is the actual
        amount of points, advertised by PCode.
    
    v3: - Extended restricted qgv point mask to 0xf, as we have now
          3:2 bits for PSF GV points(Matt Roper)
        - Replaced val2 with NULL from PCode request, since its not being
          used(Matt Roper)
        - Replaced %d to 0x%x for better readability(thanks for spotting)
    Signed-off-by: default avatarStanislav Lisovskiy <stanislav.lisovskiy@intel.com>
    Cc: Matt Roper <matthew.d.roper@intel.com>
    Reviewed-by: default avatarMatt Roper <matthew.d.roper@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20210531064845.4389-2-stanislav.lisovskiy@intel.com
    192fbfb7
intel_dram.c 12.6 KB