Hi,
On Thu, Jul 13, 2017 at 10:41 PM, Maxime Ripard maxime.ripard@free-electrons.com wrote:
In the earlier display engine designs, any register access while a commit is pending is forbidden.
One of the symptoms is that reading a register will return another, random, register value which can lead to register corruptions if we ever do a read/modify/write cycle.
Alternatively, if changes to the backend (layers) are guaranteed to happen while the CRTC is disabled (which seems to be the case after looking at drm_atomic_helper_commit_planes and drm_atomic_helper_commit_tail), we could just turn on register auto-commit all the time and not deal with this.
ChenYu
Signed-off-by: Maxime Ripard maxime.ripard@free-electrons.com
drivers/gpu/drm/sun4i/sun4i_backend.c | 14 ++++++++++++++ drivers/gpu/drm/sun4i/sun4i_crtc.c | 1 + 2 files changed, 15 insertions(+)
diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c index cf480218daa5..ce1f40f7511e 100644 --- a/drivers/gpu/drm/sun4i/sun4i_backend.c +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c @@ -67,6 +67,19 @@ static void sun4i_backend_commit(struct sunxi_engine *engine) SUN4I_BACKEND_REGBUFFCTL_LOADCTL); }
+static int sun4i_backend_commit_poll(struct sunxi_engine *engine) +{
u32 val;DRM_DEBUG_DRIVER("Polling for the commit to end\n");return regmap_read_poll_timeout(engine->regs,SUN4I_BACKEND_REGBUFFCTL_REG,val,!(val & SUN4I_BACKEND_REGBUFFCTL_LOADCTL),100, 50000);+}
void sun4i_backend_layer_enable(struct sun4i_backend *backend, int layer, bool enable) { @@ -330,6 +343,7 @@ static int sun4i_backend_of_get_id(struct device_node *node)
static const struct sunxi_engine_ops sun4i_backend_engine_ops = { .commit = sun4i_backend_commit,
.commit_poll = sun4i_backend_commit_poll, .layers_init = sun4i_layers_init, .apply_color_correction = sun4i_backend_apply_color_correction, .disable_color_correction = sun4i_backend_disable_color_correction,diff --git a/drivers/gpu/drm/sun4i/sun4i_crtc.c b/drivers/gpu/drm/sun4i/sun4i_crtc.c index 2eba1d8639d8..31550493fa1d 100644 --- a/drivers/gpu/drm/sun4i/sun4i_crtc.c +++ b/drivers/gpu/drm/sun4i/sun4i_crtc.c @@ -34,6 +34,7 @@ static void sun4i_crtc_atomic_begin(struct drm_crtc *crtc, struct drm_crtc_state *old_state) { struct sun4i_crtc *scrtc = drm_crtc_to_sun4i_crtc(crtc);
struct sunxi_engine *engine = scrtc->engine; struct drm_device *dev = crtc->dev; unsigned long flags;-- git-series 0.9.1