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On 13/06/17 12:02, Tomi Valkeinen wrote:
> Seems that on omap3 enabling a crtc without any planes causes a sync
> lost flood. This only happens on the first enable, and after that it
> works. This looks like an HW issue.
>
> It's unclear why this is happening or how to fix it, but as a quick
> work-around, this patch enables i734 errata work-around for omap2 and
> omap3 too. The errata work-around enables and disables the LCD output
> with a plane once when waking up the DSS IP, and it seems to resolve the
> omap3 problem too. It is unclear if omap2 has the same issue, but it
> probably has and the WA should have no side effects so it should be safe
> to enable on omap2 too.
I was again debugging and testing this problem, and I don't think this patch
works very well. I'm getting endless sync losts again.
Here's another try, this time changing how the omapdrm commits the new setup.
At least for me this seems to work better.
Tomi
>From fc5cc9678e130196012c17b37e555d53d3d3476b Mon Sep 17 00:00:00 2001
From: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
Date: Wed, 23 Aug 2017 12:19:02 +0300
Subject: [PATCHv2] drm/omap: work-around for omap3 display enable
Seems that on omap3 enabling a crtc without any planes causes a sync
lost flood. This only happens on the first enable, and after that it
works. This looks like an HW issue and it's unclear why this is
happening or how to fix it.
This started happening after 897145d0c7010b4e07fa9bc674b1dfb9a2c6fff9
("drm/omapdrm: Move commit_modeset_enables() before commit_planes()")
which, as a work-around, changed omapdrm first to do the modeset enable,
and plane set only after that. This WA should be fine on all DSS
versions, but apparently OMAP3 DSS is an exception.
This patch reverts that work-around for OMAP3 DSS.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxx>
---
drivers/gpu/drm/omapdrm/omap_drv.c | 47 ++++++++++++++++++++++++--------------
1 file changed, 30 insertions(+), 17 deletions(-)
diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
index 9b3c36b48356..cdf5b0601eba 100644
--- a/drivers/gpu/drm/omapdrm/omap_drv.c
+++ b/drivers/gpu/drm/omapdrm/omap_drv.c
@@ -84,23 +84,36 @@ static void omap_atomic_commit_tail(struct drm_atomic_state *old_state)
/* Apply the atomic update. */
drm_atomic_helper_commit_modeset_disables(dev, old_state);
- /* With the current dss dispc implementation we have to enable
- * the new modeset before we can commit planes. The dispc ovl
- * configuration relies on the video mode configuration been
- * written into the HW when the ovl configuration is
- * calculated.
- *
- * This approach is not ideal because after a mode change the
- * plane update is executed only after the first vblank
- * interrupt. The dispc implementation should be fixed so that
- * it is able use uncommitted drm state information.
- */
- drm_atomic_helper_commit_modeset_enables(dev, old_state);
- omap_atomic_wait_for_completion(dev, old_state);
-
- drm_atomic_helper_commit_planes(dev, old_state, 0);
-
- drm_atomic_helper_commit_hw_done(old_state);
+ if (priv->omaprev != 0x3430) {
+ /* With the current dss dispc implementation we have to enable
+ * the new modeset before we can commit planes. The dispc ovl
+ * configuration relies on the video mode configuration been
+ * written into the HW when the ovl configuration is
+ * calculated.
+ *
+ * This approach is not ideal because after a mode change the
+ * plane update is executed only after the first vblank
+ * interrupt. The dispc implementation should be fixed so that
+ * it is able use uncommitted drm state information.
+ */
+ drm_atomic_helper_commit_modeset_enables(dev, old_state);
+ omap_atomic_wait_for_completion(dev, old_state);
+
+ drm_atomic_helper_commit_planes(dev, old_state, 0);
+
+ drm_atomic_helper_commit_hw_done(old_state);
+ } else {
+ /*
+ * OMAP3 DSS seems to have issues with the work-around above,
+ * resulting in endless sync losts if a crtc is enabled without
+ * a plane. For now, skip the WA for OMAP3.
+ */
+ drm_atomic_helper_commit_planes(dev, old_state, 0);
+
+ drm_atomic_helper_commit_modeset_enables(dev, old_state);
+
+ drm_atomic_helper_commit_hw_done(old_state);
+ }
/*
* Wait for completion of the page flips to ensure that old buffers
--
2.7.4
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