mipmap option 3. Actually maybe a separate tri-linear option will be better
m_mipmap == 2 => use manual PS2 trilinear/mipmap
Otherwise
m_filter == 3 => always use full automatic trilinear interpolation
m_filter == 4 => use automatic trilinear interpolation when PS2 uses mipmap
m_filter == 5 => like 4 but force bilinear interpolation inside layer