[PATCH 4.9 055/109] drm/exynos/decon5433: update shadow registers iff there are active windows

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrzej Hajda <a.hajda@xxxxxxxxxxx>


[ Upstream commit f65a7c9cb3770ed4d3e7c57c66d7032689081b5e ]

Improper usage of DECON_UPDATE register leads to subtle errors.
If it set in decon_commit when there are no active windows it results
in slow registry updates - all subsequent shadow registry updates takes more
than full vblank. On the other side if it is not set when there are
active windows it results in garbage on the screen after suspend/resume of
FB console.

The patch hopefully fixes it.

Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/exynos/exynos5433_drm_decon.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
+++ b/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
@@ -188,8 +188,6 @@ static void decon_commit(struct exynos_d
 
 	/* enable output and display signal */
 	decon_set_bits(ctx, DECON_VIDCON0, VIDCON0_ENVID | VIDCON0_ENVID_F, ~0);
-
-	decon_set_bits(ctx, DECON_UPDATE, STANDALONE_UPDATE_F, ~0);
 }
 
 static void decon_win_set_pixfmt(struct decon_context *ctx, unsigned int win,
@@ -340,8 +338,9 @@ static void decon_atomic_flush(struct ex
 	for (i = ctx->first_win; i < WINDOWS_NR; i++)
 		decon_shadow_protect_win(ctx, i, false);
 
-	/* standalone update */
-	decon_set_bits(ctx, DECON_UPDATE, STANDALONE_UPDATE_F, ~0);
+	/* update iff there are active windows */
+	if (crtc->base.state->plane_mask)
+		decon_set_bits(ctx, DECON_UPDATE, STANDALONE_UPDATE_F, ~0);
 
 	if (ctx->out_type & IFTYPE_I80)
 		set_bit(BIT_WIN_UPDATED, &ctx->flags);