RADEON_PCIE_TX_GART_START_LO
WREG32_PCIE(RADEON_PCIE_TX_GART_START_LO, rdev->mc.gtt_start);
WREG32_PCIE(RADEON_PCIE_TX_GART_START_LO, 0);
tmp = RREG32_PCIE(RADEON_PCIE_TX_GART_START_LO);