[patch 0/8] RFC: Pinebook pro EDP support

[Alper Nebi Yasak]

On 25/09/2020 21:36, Arnaud Patard (Rtp) wrote:
> This patchset add support for the rk3399 edp. It has been tested on the pinebook
> pro devices. The only missing part is a hack used to get stable edp output after
> a warn reset, which is possibly specific to this device. I'm not sure if it's suitable
> for merge.
> 
> The changes have been written by studying the linux code, since I didn't find any
> manual for theses part of the RK3399 SoC.
> 
> On the linux kernel side, on recent kernels, it needs commit "pwm: rockchip: Keep enabled PWMs
> running while probing" otherwise the pinebook pro will freeze when probing
> the display.
> 
> The kernel is also randomly failing to display something on my device. When this
> occurs, the kernel has this following message:
> rockchip-pm-domain ff310000.power-management:power-controller: failed to set idle on domain 'pd_vopl', val=0
> I've yet to find what's the issue.

I've been trying to test your patches on a rk3399-gru-kevin with these
patches and as a result I've posted some patches for cros_ec_pwm as a
backlight [1], and have some yet-to-be-posted ones for kevin and bob
because I don't truly know if they work [2]. (I don't even have the
appropriate hardware to get a serial console / debug this board, thus
the motivation to get the screen working).

It should be possible for someone with a kevin or bob to tinker on my
test branch and get more conclusive outcomes than I did, maybe even get
everything fully working!

[1] https://patchwork.ozlabs.org/project/uboot/list/?series=204353
[2] https://github.com/alpernebbi/u-boot/commits/rk3399-gru-kevin/wip


Anyway, here's how it goes for me. I start from the Chrome OS firmware
showing some white-background bitmap on the screen with the backlight
enabled. I press CTRL+L to tell it to chainload my U-Boot build. I don't
know if/how chainloading this way affects any of this.

AFAICT, the firmware doesn't clear or turn off the backlight before
doing so, because when VIDEO_ROCKCHIP_MAX_{X,Y}RES={3840,2160} the
screen doesn't clear. I have to set {2400,1600} as it's the resolution
of my panel. Maybe you should test this on Pinebook Pro as well, the
defaults are {1920,1080} (same as its panel), but DISPLAY_ROCKCHIP_HDMI
for example would change it.

With those initial conditions I see the the screen progressively
clearing to black then the backlight turns off after a while. I think
the clearing part hints this patchset is at least doing something.

I had also tried commenting out "enable-gpios" code in pwm_backlight.c
(when I didn't really know how to turn it on properly), that results in
the backlight turn on immediately after it turns off, where I see a
small white artifact (?) on the mid-right part of the bottom of the
screen, for a frame or so.

Overall, I never see any content on the display and it's always black.
Even unsetting CONFIG_SYS_WHITE_ON_BLACK doesn't change anything.

Wish I could've been more helpful, but all this is as far as I could
figure out right now.