[Letux-kernel] 5.2-rc1 + display

H. Nikolaus Schaller hns at goldelico.com
Mon May 27 09:54:00 CEST 2019

> Am 27.05.2019 um 08:17 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> Hi Andreas,
>> Am 27.05.2019 um 08:07 schrieb Andreas Kemnade <andreas at kemnade.info>:
>> Hi,
>> I just booted a 5.2-rc1 (mainline + config copied in). The display on the
>> gta04a5 works. There were rumours that everything regarding displays is broken.
> Yes, it was broken. The problem is the infamous spi-cs-high issue...
> See: http://git.goldelico.com/?p=letux-kernel.git;a=commit;h=07d04c8d897b8e154cc7dcf3d6161c22991da430
> Maybe something is different enough if you merge versions manually.

Or if I remember correctly, there could have been an otherwise unnoticed hardware bug that on your GTA04A5 the CS
of the panel is always high and not controlled by the OMAP. This would hide all changes around spi-cs-high.

A different question is why it did work on 4.19/4.20/5.0/5.1 after gpiolib introduced the spi-cs-high legacy handler.
I think the legacy handler did have several bugs which we did fix in those kernel versions, and upstream did try to
fix in parallel. So the result may have been that in those kernels up to 5.1 the legacy detector didn't work properly,
and our not-for-legacy-prepared device tree did work... And with 5.2-rc1 they finally fixed the legacy handler code
which finally broke our DTS.

That is at least some theory... No need to verify since I don't think we can learn anything from it. Just that it
is a sisyphean task to work on upstream kernels.

> The L3704 and L7004 displays were broken differently. Because the omap-dpi driver
> was removed. I have patches for the generic drm-dpi driver.
> BR,
> Nikolaus
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