diff --git a/drivers/gpu/drm/radeon/radeon_legacy_encoders.c b/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
index 981508f..38e45e2 100644
--- a/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_legacy_encoders.c
@@ -46,6 +46,7 @@
 	struct radeon_encoder *radeon_encoder = to_radeon_encoder(encoder);
 	uint32_t lvds_gen_cntl, lvds_pll_cntl, pixclks_cntl, disp_pwr_man;
 	int panel_pwr_delay = 2000;
+	bool is_mac = false;
 	DRM_DEBUG("\n");
 
 	if (radeon_encoder->enc_priv) {
@@ -58,6 +59,15 @@
 		}
 	}
 
+	/* macs (and possibly some x86 oem systems?) wire up LVDS strangely
+	 * Taken from radeonfb.
+	 */
+	if ((rdev->mode_info.connector_table == CT_IBOOK) ||
+	    (rdev->mode_info.connector_table == CT_POWERBOOK_EXTERNAL) ||
+	    (rdev->mode_info.connector_table == CT_POWERBOOK_INTERNAL) ||
+	    (rdev->mode_info.connector_table == CT_POWERBOOK_VGA))
+		is_mac = true;
+
 	switch (mode) {
 	case DRM_MODE_DPMS_ON:
 		disp_pwr_man = RREG32(RADEON_DISP_PWR_MAN);
@@ -74,6 +84,8 @@
 
 		lvds_gen_cntl = RREG32(RADEON_LVDS_GEN_CNTL);
 		lvds_gen_cntl |= (RADEON_LVDS_ON | RADEON_LVDS_EN | RADEON_LVDS_DIGON | RADEON_LVDS_BLON);
+		if (is_mac)
+			lvds_gen_cntl |= RADEON_LVDS_BL_MOD_EN;
 		lvds_gen_cntl &= ~(RADEON_LVDS_DISPLAY_DIS);
 		udelay(panel_pwr_delay * 1000);
 		WREG32(RADEON_LVDS_GEN_CNTL, lvds_gen_cntl);
@@ -85,7 +97,14 @@
 		WREG32_PLL_P(RADEON_PIXCLKS_CNTL, 0, ~RADEON_PIXCLK_LVDS_ALWAYS_ONb);
 		lvds_gen_cntl = RREG32(RADEON_LVDS_GEN_CNTL);
 		lvds_gen_cntl |= RADEON_LVDS_DISPLAY_DIS;
-		lvds_gen_cntl &= ~(RADEON_LVDS_ON | RADEON_LVDS_BLON | RADEON_LVDS_EN | RADEON_LVDS_DIGON);
+		if (is_mac) {
+			lvds_gen_cntl &= ~RADEON_LVDS_BL_MOD_EN;
+			WREG32(RADEON_LVDS_GEN_CNTL, lvds_gen_cntl);
+			lvds_gen_cntl &= ~(RADEON_LVDS_ON | RADEON_LVDS_EN);
+		} else {
+			WREG32(RADEON_LVDS_GEN_CNTL, lvds_gen_cntl);
+			lvds_gen_cntl &= ~(RADEON_LVDS_ON | RADEON_LVDS_BLON | RADEON_LVDS_EN | RADEON_LVDS_DIGON);
+		}
 		udelay(panel_pwr_delay * 1000);
 		WREG32(RADEON_LVDS_GEN_CNTL, lvds_gen_cntl);
 		WREG32_PLL(RADEON_PIXCLKS_CNTL, pixclks_cntl);