[Letux-kernel] regression: drm/omapdrm: Move commit_modeset_enables() before commit_planes()

Jyri Sarha jsarha at ti.com
Wed Apr 19 17:49:39 CEST 2017

On 04/19/17 16:35, Tomi Valkeinen wrote:
> I was able to reproduce on my very old omap3 beagleboard. Looks very
> much like a omap3 DSS HW bug to me. The unfortunate thing is that even
> reverting the patch won't remove the issue, if the userspace happens to
> configure things in certain order.
> It looks to me that if the DSS output is enabled without an overlay (the
> primary plane, normally), DSS gets stuck into a bad state, and only
> reboot helps (because we can't reset, there's no omap hwmod reset
> framework).
> But there should be nothing wrong with that setup, and if there's first
> been a successful display enable, then later we can enable the DSS
> without any planes.

If that is the case, then maybe we could just enable errata i734 (the
gamma bug) work a round for omap3 too. The work a round makes an
artificial minimal display setup with GFX plane for one frame, with
outputs masked, so it could be exactly what we need.

Testing that should be as simple as setting has_gamma_i734_bug true in
struct dispc_features omap34xx_rev1_0_dispc_feats. However, it may look
weird since the omap3 does not even have gamma support.

Best regards,

> So... At the moment, I have no idea how to fix it. Reverting the patch
> will cause other things to start breaking, but perhaps that's the only
> option as a short term kind-of-fix.
>  Tomi

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