[PATCH AUTOSEL for 4.9 22/54] drm/exynos/decon5433: update shadow registers iff there are active windows

[alexander.levin@verizon.com]

From: Andrzej Hajda <a.hajda@samsung.com>

[ 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@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
---
 drivers/gpu/drm/exynos/exynos5433_drm_decon.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c b/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
index 6ca1f3117fe8..ef7fcb5f044b 100644
--- 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_drm_crtc *crtc)
 
 	/* 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 exynos_drm_crtc *crtc)
 	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);
-- 
2.11.0