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

H. Nikolaus Schaller hns at goldelico.com
Tue Nov 20 10:17:25 CET 2018


> Am 19.11.2018 um 15:18 schrieb Sebastian Reichel <sre at kernel.org>:
> Hi,
> On Mon, Nov 19, 2018 at 02:55:35PM +0100, H. Nikolaus Schaller wrote:
>>> Am 19.11.2018 um 14:11 schrieb Sebastian Reichel <sre at kernel.org>:
>>> On Mon, Nov 19, 2018 at 02:38:38PM +0200, Tomi Valkeinen wrote:
>>>> On 19/11/18 14:29, H. Nikolaus Schaller wrote:
>>> My series:
>>> patch 1:   Simple cleanup
>>> patch 2-4: General DSI fixes for the kernel changes in 4.20-rc1. I think
>>>          they are also relevant for DSI video mode panels.
>>> patch 5-6: Only relevant for DSI command mode. It's not really DSI
>>>          specific and should not make a difference on any outputs
>>>          not setting OMAP_DSS_DISPLAY_CAP_MANUAL_UPDATE.
>>> -- Sebastian
>> but the video mode panel doesn't call enable(). It did up to
>> 4.19.0 and stopped in 4.20-rc1.
> Ok.
>> So how can I debug the panel->enable()?
>> Where should it be called from dss core?
>> Then I could check the conditions to call enable().
> This is called in omap_encoder_enable(). For debugging I suggest to
> add "drm.debug=0xf" kernel argument. "drm/omap: don't check dispc
> timings for DSI" fixes a similar problem for panel-dsi-cm.

I have checked that and it looks all reasonable and I did enable
the same on the 4.19 kernel and they are basically the same (some
not obviously significant diffs in sequence or connector numbers).

The main difference is that after

[   10.811910] [drm:omap_fbdev_create [omapdrm]] allocated 720x1280 fb

there is no more drm activity on 4.20-rc3 but on 4.19 there is.
And there, the panel enable() is called.

Another diff is

4.20: [drm:pdev_probe [omapdrm]] registered 4 planes, 2 crtcs, 2 encoders and 2 connectors
4.19: [drm:pdev_probe [omapdrm]] registered 4 planes, 2 crtcs/encoders/connectors

but I am not sure if this is just a cosmetic change or if encoders/connectors are missing.

So I have no more ideas how to find out why the panel is not becoming enabled.

BR and thanks,

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