1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_atombios.c b/drivers/gpu/drm/radeon/radeon_atombios.c
index fecd705a1a5f..933a2cd7bb55 100644
--- a/drivers/gpu/drm/radeon/radeon_atombios.c
+++ b/drivers/gpu/drm/radeon/radeon_atombios.c
@@ -181,6 +181,18 @@ void radeon_atombios_i2c_init(struct radeon_device *rdev)
                         gpio = &i2c_info->asGPIO_Info[i];
                         i2c.valid = false;
 
+                        /* r4xx mask is technically not used by the hw, so patch in the legacy mask bits */
+                        if ((rdev->family == CHIP_R420) ||
+                            (rdev->family == CHIP_R423) ||
+                            (rdev->family == CHIP_RV410)) {
+                                if ((le16_to_cpu(gpio->usClkMaskRegisterIndex) == 0x0018) ||
+                                    (le16_to_cpu(gpio->usClkMaskRegisterIndex) == 0x0019) ||
+                                    (le16_to_cpu(gpio->usClkMaskRegisterIndex) == 0x001a)) {
+                                        gpio->ucClkMaskShift = 0x19;
+                                        gpio->ucDataMaskShift = 0x18;
+                                }
+                        }
+
                         /* some evergreen boards have bad data for this entry */
                         if (ASIC_IS_DCE4(rdev)) {
                                 if ((i == 7) &&