On Mon, Jul 31, 2023 at 07:03:07PM +0200, Maxime Ripard wrote:

Hi,

On Mon, Jul 31, 2023 at 11:33:22AM -0500, Chris Morgan wrote:

quoted

In my case a few different panel drivers disable the regulators in the
unprepare/disable routines.

And that's totally fine.

quoted

For at least the Rockchip DSI implementations for some reason the
panel gets unprepared more than once, which triggers an unbalanced
regulator disable.

"For some reason" being that DW-DSI apparently finds it ok to bypass any
kind of abstraction and randomly calling panel functions by itself:

https://elixir.bootlin.com/linux/v6.4.7/source/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c#L868

It looks like it's fixed it current drm-misc-next though.

Good, when I get a chance I will test it out with the existing panels
I have at my disposal and submit some patches to clean them up.

quoted

Obviously though the correct course of action is to fix the reason why
the panel is disabled more than once, but that's at least the root
cause of this behavior on the few panels I've worked with.

Like I said we already have a commit on the way to fix that, so it
shouldn't be an issue anymore.

I stand by what I was saying earlier though, I think it's mostly
cargo-cult or drivers being very wrong. If anything, the DW-DSI stuff
made me even more convinced that we shouldn't even entertain that idea
:)

Maxime

Thank you, and yes if a driver is doing something it shouldn't we
shouldn't be patching around that, we should be fixing things. Thanks
for providing me with the additional info.

Chris