drm/radeon/kms: add new radeon_info ioctl query for clock crystal freq

Needed for timer queries in the 3D driver.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>
diff --git a/drivers/gpu/drm/radeon/radeon_kms.c b/drivers/gpu/drm/radeon/radeon_kms.c
index 28a53e4a..9832129 100644
--- a/drivers/gpu/drm/radeon/radeon_kms.c
+++ b/drivers/gpu/drm/radeon/radeon_kms.c
@@ -201,6 +201,10 @@
 		}
 		radeon_set_filp_rights(dev, &rdev->cmask_filp, filp, &value);
 		break;
+	case RADEON_INFO_CLOCK_CRYSTAL_FREQ:
+		/* return clock value in KHz */
+		value = rdev->clock.spll.reference_freq * 10;
+		break;
 	default:
 		DRM_DEBUG_KMS("Invalid request %d\n", info->request);
 		return -EINVAL;