drm/sun4i: tcon: multiply the vtotal when not in interlace

It appears that the total vertical resolution needs to be doubled when
we're not in interlaced. Make sure that is the case.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

1 files changed, 22 insertions, 4 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 61e1de77831d..d9791292553e 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -229,7 +229,7 @@ EXPORT_SYMBOL(sun4i_tcon0_mode_set);
 void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon,
                           struct drm_display_mode *mode)
 {
-        unsigned int bp, hsync, vsync;
+        unsigned int bp, hsync, vsync, vtotal;
         u8 clk_delay;
         u32 val;
 
@@ -276,12 +276,30 @@ void sun4i_tcon1_mode_set(struct sun4i_tcon *tcon,
                      SUN4I_TCON1_BASIC3_H_TOTAL(mode->crtc_htotal) |
                      SUN4I_TCON1_BASIC3_H_BACKPORCH(bp));
 
-        /* Set vertical display timings */
         bp = mode->crtc_vtotal - mode->crtc_vsync_start;
         DRM_DEBUG_DRIVER("Setting vertical total %d, backporch %d\n",
-                         mode->vtotal, bp);
+                         mode->crtc_vtotal, bp);
+
+        /*
+         * The vertical resolution needs to be doubled in all
+         * cases. We could use crtc_vtotal and always multiply by two,
+         * but that leads to a rounding error in interlace when vtotal
+         * is odd.
+         *
+         * This happens with TV's PAL for example, where vtotal will
+         * be 625, crtc_vtotal 312, and thus crtc_vtotal * 2 will be
+         * 624, which apparently confuses the hardware.
+         *
+         * To work around this, we will always use vtotal, and
+         * multiply by two only if we're not in interlace.
+         */
+        vtotal = mode->vtotal;
+        if (!(mode->flags & DRM_MODE_FLAG_INTERLACE))
+                vtotal = vtotal * 2;
+
+        /* Set vertical display timings */
         regmap_write(tcon->regs, SUN4I_TCON1_BASIC4_REG,
-                     SUN4I_TCON1_BASIC4_V_TOTAL(mode->vtotal) |
+                     SUN4I_TCON1_BASIC4_V_TOTAL(vtotal) |
                      SUN4I_TCON1_BASIC4_V_BACKPORCH(bp));
 
         /* Set Hsync and Vsync length */