[Letux-kernel] Debugging 4.11-rc6 on GTA04

Andreas Kemnade andreas at kemnade.info
Fri Apr 14 16:02:13 CEST 2017

On Thu, 13 Apr 2017 17:56:08 +0200
"H. Nikolaus Schaller" <hns at goldelico.com> wrote:

> Hi Andreas,
> > Am 12.04.2017 um 07:07 schrieb Andreas Kemnade <andreas at kemnade.info>:
> --- snip ---
> >> Maybe mainline has another bug. Or our latest patches trigger that in 4.11
> >> but not in 4.10.
> >> 
> > Display problems seem to start with this patch:
> > 
> > 897145d0c7010b4e07fa9bc674b1dfb9a2c6fff9 is the first bad commit
> > commit 897145d0c7010b4e07fa9bc674b1dfb9a2c6fff9
> > Author: Jyri Sarha <jsarha at ti.com>
> > Date:   Fri Jan 27 12:04:55 2017 +0200
> > 
> >    drm/omapdrm: Move commit_modeset_enables() before commit_planes()
> > 
> >    Move drm_atomic_helper_commit_modeset_enables() call to before
> >    drm_atomic_helper_commit_planes() call and have a
> >    omap_atomic_wait_for_completion() call after both.
> > 
> >    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.  information.
> ***should*** probably means it does not :(
> I wonder why Tomi did approve that. I think we should discuss with him
> or ask to revert?
yes, i thnk so.

> Maybe this bug is hidden with my setup of loaded kernel modules and other
> letux-base patches which modify initialization sequence? Or it depends
> on other details.
I could reproduce that with letux_defconfig. Then I reverted said patch.
No display problem.
Then I checked out HEAD^ (so again at 1467f43)
compiled modules and just copied omapdrm to sd card.
Again no display problem!
I changed kernel commandline to init=/init-measure-current.sh
which loads stuff piece by piece and measures current
Now the display problem is there again.
So it depends on module load order/timing. And the order is perhaps
influenced by the order in which the modules are copied to the sdcard.

> > kernel config used is attached. I have compiled statically most of the
> > twl4030 / usb stuff because we have patches in our feature branches to
> > make that work as modules.
> Yes, indeed. I should try to upstream such things...
Especially I am talking about this:
commit ea858c8cdbcb2758458cbcc003e61041d75aa31f
Author: H. Nikolaus Schaller <hns at goldelico.com>

    drivers:power:twl4030-charger: don't check if battery is present

commit fe605a5f153e8612475c460ba0714e45f3aecd3e
Author: H. Nikolaus Schaller <hns at goldelico.com>

    fix: reorder to check resources first

commit ee7bfe0377e7cfc1e14d80f241eb990a0b8cf8d9
Author: H. Nikolaus Schaller <hns at goldelico.com>

    drivers:power:twl4030-charger: fix problem with EPROBE_DEFER

commit 9d7b2d776637c2d132883728b6c9ff4e939d1861
Author: H. Nikolaus Schaller <hns at goldelico.com>

    drivers:power:twl4030-charger: don't return after allocating irq

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