RADEON_DAC2_DAC2_CLK_SEL
dac2_cntl |= RADEON_DAC2_DAC2_CLK_SEL;
dac2_cntl = RREG32(RADEON_DAC_CNTL2) & ~RADEON_DAC2_DAC2_CLK_SEL;
dac2_cntl = RREG32(RADEON_DAC_CNTL2) | RADEON_DAC2_DAC2_CLK_SEL;
WREG32(RADEON_DAC_CNTL2, RADEON_DAC2_DAC2_CLK_SEL);
tmp = dac_cntl2 & ~RADEON_DAC2_DAC2_CLK_SEL;
tmp = dac_cntl2 | RADEON_DAC2_DAC2_CLK_SEL | RADEON_DAC2_CMP_EN;