Re: [PATCH 04/10] ARM: dts: rockchip: add startup delay to rk3288-veyron panel-regulators

Re: [PATCH 04/10] ARM: dts: rockchip: add startup delay to rk3288-veyron panel-regulators

[Doug Anderson]

Hi,

On Wed, Fri, 18 Mar 2016 Heiko Stuebner <heiko@sntech.de> wrote:
>
> The panels need a bit of time to actually turn on. If this isn't
> observed, this results in problems when trying talk to the panels
> and thus produces detection errors. 100ms seem to be a safe value
> for the time being.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
>  arch/arm/boot/dts/rk3288-veyron-jaq.dts    | 1 +
>  arch/arm/boot/dts/rk3288-veyron-jerry.dts  | 1 +
>  arch/arm/boot/dts/rk3288-veyron-minnie.dts | 1 +
>  arch/arm/boot/dts/rk3288-veyron-speedy.dts | 1 +
>  4 files changed, 4 insertions(+)

I know it was 3 years ago, but any idea how to reproduce the problems
you were seeing without this patch?  I believe the downstream kernel
never had any delay like this and I'm not aware of any issues.

I wonder if the need for this extra 100 ms delay is no longer there
now that we have:

3157694d8c7f pwm-backlight: Add support for PWM delays proprieties.
5fb5caee92ba pwm-backlight: Enable/disable the PWM before/after LCD
enable toggle.
6d5922dd0d60 ARM: dts: rockchip: set PWM delay backlight settings for Veyron

Re: [PATCH 04/10] ARM: dts: rockchip: add startup delay to rk3288-veyron panel-regulators

[Heiko Stübner]

Hi Doug,

Am Donnerstag, 20. Juni 2019, 03:27:55 CEST schrieb Doug Anderson:
> On Wed, Fri, 18 Mar 2016 Heiko Stuebner <heiko@sntech.de> wrote:
> >
> > The panels need a bit of time to actually turn on. If this isn't
> > observed, this results in problems when trying talk to the panels
> > and thus produces detection errors. 100ms seem to be a safe value
> > for the time being.
> >
> > Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> > ---
> >  arch/arm/boot/dts/rk3288-veyron-jaq.dts    | 1 +
> >  arch/arm/boot/dts/rk3288-veyron-jerry.dts  | 1 +
> >  arch/arm/boot/dts/rk3288-veyron-minnie.dts | 1 +
> >  arch/arm/boot/dts/rk3288-veyron-speedy.dts | 1 +
> >  4 files changed, 4 insertions(+)
> 
> I know it was 3 years ago, but any idea how to reproduce the problems
> you were seeing without this patch?  I believe the downstream kernel
> never had any delay like this and I'm not aware of any issues.
>
> I wonder if the need for this extra 100 ms delay is no longer there
> now that we have:
> 
> 3157694d8c7f pwm-backlight: Add support for PWM delays proprieties.
> 5fb5caee92ba pwm-backlight: Enable/disable the PWM before/after LCD
> enable toggle.
> 6d5922dd0d60 ARM: dts: rockchip: set PWM delay backlight settings for Veyron

I just did a non-scientific test on my jerry+minnie and yes, simply
reverting that patch does not seem to affect display bringup and I still
get a prompt.

So I guess we could just revert that patch in light of the changes.
[patches welcome ;-) ]

Heiko