[Letux-kernel] DSI panels with omapdrm on 4.20-rc

Tomi Valkeinen tomi.valkeinen at ti.com
Thu Dec 20 09:21:28 CET 2018

On 19/12/18 18:36, H. Nikolaus Schaller wrote:
> Hi Tomi,
>> Am 19.12.2018 um 10:30 schrieb Tomi Valkeinen <tomi.valkeinen at ti.com>:
>> On 18/12/18 20:09, H. Nikolaus Schaller wrote:
>>>> Comparing it to the (mostly) working kernel, I found out that the bus
>>>> flags are again broken. I attached a quick hack patch that seems to fix
>>>> them, and with that I get a working 400x400 plane, but underflows with
>>>> full-screen plane.
>>>> I couldn't quite figure out how to fix the bus-flags correctly, though.
>>> Hm. For me this patch does not make a difference.
>>> But I think we are close to a solution.
>> Ok... Well, the VC stuff works ok for me, as far as I see.
>> I pushed my hacky test branch to:
>> git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux.git
>> 4.20/omap5-video-dsi-test
>> It has one additional fix "fix dsi depopulate", which is needed if you
>> want to unload modules.
> It seems as if that one already makes the difference!

You mean it works now for you?

>> The only problem with my branch are FIFO underflows. Apparently these
>> were present on older kernels too, and is probably somehow related to
>> horizontal blanking. 1080x1920 plane causes underflows, but 1000x1920
>> does not.
> I haven't seen that but it might be that if horizontal blanking is
> too short, it might not be enough to send long DCS commands.

Hmm I don't think it's related to DCS, as this happens when no commands
are being sent. And the DSI side shouldn't affect DISPC, where the
underflows are coming from.

> So in summary I have added these patches not yet in v4.20-rc7 (plus the panel driver):
> b2b80dbeff3a fix dsi depopulate
> 2ef5e09c79d9 drm/omap: hackfix dsi bus flags
> b8aedc2b8295 drm/omap: fix crash in DSI debug dumps
> 5cceb44e03e3 drm/omap: add support for manually updated displays
> 87dfb765c3be drm/omap: add framedone interrupt support
> 50f581c97fbe drm/omap: fix incorrect union usage
> 977e0c2e641f drm/omap: don't check dispc timings for DSI
> f62952e37eae drm/omap: use DRM_DEBUG_DRIVER instead of CORE
> Do you plan to get these fixes already into v4.20.0?

Are you sure you're on -rc7? At least "drm/omap: fix incorrect union
usage" is in -rc7.


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