1 files changed, 26 insertions, 1 deletions

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_slave.c b/drivers/gpu/drm/tilcdc/tilcdc_slave.c
index dfffaf014022..23b3203d8241 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_slave.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_slave.c
@@ -73,13 +73,38 @@ static void slave_encoder_prepare(struct drm_encoder *encoder)
         tilcdc_crtc_set_panel_info(encoder->crtc, &slave_info);
 }
 
+static bool slave_encoder_fixup(struct drm_encoder *encoder,
+                const struct drm_display_mode *mode,
+                struct drm_display_mode *adjusted_mode)
+{
+        /*
+         * tilcdc does not generate VESA-complient sync but aligns
+         * VS on the second edge of HS instead of first edge.
+         * We use adjusted_mode, to fixup sync by aligning both rising
+         * edges and add HSKEW offset to let the slave encoder fix it up.
+         */
+        adjusted_mode->hskew = mode->hsync_end - mode->hsync_start;
+        adjusted_mode->flags |= DRM_MODE_FLAG_HSKEW;
+
+        if (mode->flags & DRM_MODE_FLAG_NHSYNC) {
+                adjusted_mode->flags |= DRM_MODE_FLAG_PHSYNC;
+                adjusted_mode->flags &= ~DRM_MODE_FLAG_NHSYNC;
+        } else {
+                adjusted_mode->flags |= DRM_MODE_FLAG_NHSYNC;
+                adjusted_mode->flags &= ~DRM_MODE_FLAG_PHSYNC;
+        }
+
+        return drm_i2c_encoder_mode_fixup(encoder, mode, adjusted_mode);
+}
+
+
 static const struct drm_encoder_funcs slave_encoder_funcs = {
                 .destroy        = slave_encoder_destroy,
 };
 
 static const struct drm_encoder_helper_funcs slave_encoder_helper_funcs = {
                 .dpms           = drm_i2c_encoder_dpms,
-                .mode_fixup     = drm_i2c_encoder_mode_fixup,
+                .mode_fixup     = slave_encoder_fixup,
                 .prepare        = slave_encoder_prepare,
                 .commit         = drm_i2c_encoder_commit,
                 .mode_set       = drm_i2c_encoder_mode_set,