From: Maxime Ripard <maxime.ripard@free-electrons.com>
Date: Mon, 22 Jan 2018 10:25:26 +0100
Subject: drm/sun4i: backend: Make sure we don't have a commit pending
Git-commit: dd63250c55bf26a814c957f6772e8f8683b70077
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
If we try to read the backend registers while it fetches the new values, we
end up with the value of some random register instead of the one we asked
for.
In order to prevent that, let's make sure that the very first thing we do
during our atomic modesetting is to let the commit bit come to a rest.
We don't have to worry about anything else since the only time we will
trigger a new transaction is during the atomic_commit which comes much
later.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/35604307e5bde2b85c674de79fa7c4d55700f085.1516613040.git-series.maxime.ripard@free-electrons.com
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/sun4i/sun4i_backend.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -296,6 +296,17 @@ static bool sun4i_backend_plane_uses_fro
return sun4i_backend_plane_uses_scaler(state);
}
+static void sun4i_backend_atomic_begin(struct sunxi_engine *engine,
+ struct drm_crtc_state *old_state)
+{
+ u32 val;
+
+ WARN_ON(regmap_read_poll_timeout(engine->regs,
+ SUN4I_BACKEND_REGBUFFCTL_REG,
+ val, !(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL),
+ 100, 50000));
+}
+
static int sun4i_backend_atomic_check(struct sunxi_engine *engine,
struct drm_crtc_state *crtc_state)
{
@@ -478,6 +489,7 @@ static struct sun4i_frontend *sun4i_back
}
static const struct sunxi_engine_ops sun4i_backend_engine_ops = {
+ .atomic_begin = sun4i_backend_atomic_begin,
.atomic_check = sun4i_backend_atomic_check,
.commit = sun4i_backend_commit,
.layers_init = sun4i_layers_init,