drm/radeon/kms: add workaround for dce3 ddc line vbios bug

fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=23752

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc:stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -98,6 +98,14 @@ static inline struct radeon_i2c_bus_rec radeon_lookup_i2c_gpio(struct radeon_dev
 				}
 			}
 
+			/* some DCE3 boards have bad data for this entry */
+			if (ASIC_IS_DCE3(rdev)) {
+				if ((i == 4) &&
+				    (gpio->usClkMaskRegisterIndex == 0x1fda) &&
+				    (gpio->sucI2cId.ucAccess == 0x94))
+					gpio->sucI2cId.ucAccess = 0x14;
+			}
+
 			if (gpio->sucI2cId.ucAccess == id) {
 				i2c.mask_clk_reg = le16_to_cpu(gpio->usClkMaskRegisterIndex) * 4;
 				i2c.mask_data_reg = le16_to_cpu(gpio->usDataMaskRegisterIndex) * 4;
@@ -174,6 +182,14 @@ void radeon_atombios_i2c_init(struct radeon_device *rdev)
 				}
 			}
 
+			/* some DCE3 boards have bad data for this entry */
+			if (ASIC_IS_DCE3(rdev)) {
+				if ((i == 4) &&
+				    (gpio->usClkMaskRegisterIndex == 0x1fda) &&
+				    (gpio->sucI2cId.ucAccess == 0x94))
+					gpio->sucI2cId.ucAccess = 0x14;
+			}
+
 			i2c.mask_clk_reg = le16_to_cpu(gpio->usClkMaskRegisterIndex) * 4;
 			i2c.mask_data_reg = le16_to_cpu(gpio->usDataMaskRegisterIndex) * 4;
 			i2c.en_clk_reg = le16_to_cpu(gpio->usClkEnRegisterIndex) * 4;