Re: [PATCH 2/2] drm/panel-simple: Add Innolux G156HCE-L01 panel entry

[Luca Ceresoli <luca.ceresoli@bootlin.com>]

Hi Marek,

On Thu, 3 Aug 2023 19:10:35 +0200
Marek Vasut <marex@denx.de> wrote:

> On 8/3/23 17:06, Luca Ceresoli wrote:
> > Hi Marek,
> > 
> > On Thu, 3 Aug 2023 16:25:37 +0200
> > Marek Vasut <marex@denx.de> wrote:
> >   
> >> On 8/3/23 16:23, Luca Ceresoli wrote:  
> >>> Hi Marek,  
> >>
> >> Hi,
> >>  
> >>> On Mon, 31 Jul 2023 23:02:58 +0200
> >>> Marek Vasut <marex@denx.de> wrote:
> >>>      
> >>>> Add support for Innolux G156HCE-L01 15.6" 1920x1080 24bpp
> >>>> dual-link LVDS TFT panel. Documentation is available at [1].  
> >>>
> >>> Interesting, I'm bringing up this exact panel right now and found your
> >>> patch.
> >>>      
> >>>> The middle frequency is tuned slightly upward from 70.93 MHz
> >>>> to 72 MHz, otherwise the panel shows slight flicker.  
> >>>
> >>> Using 70.93 MHz here does not show any flickering. I even tried going
> >>> in the opposite direction and set 70 MHz, and to use different
> >>> backlight settings, all without any flickering.
> >>>
> >>> Do you think you might be using a defective device? Would you have a
> >>> chance of testing another sample?  
> >>
> >> I have literally one such display.
> >>
> >> Which SoC do you use (and if applicable, which bridge) ?  
> > 
> > The panel is driven by the DSI-2 output of a i.MX8MP through a TI
> > SN65DSI84 bridge.  
> 
> I use the LT9211 , so I wonder whether this might be another Lontium 
> specific oddity.

Or maybe not. After checking the LVDS clock with an oscilloscope I
discovered I was actually sending 77 MHz. After fixing it I found that
my panel (of which I only have one sample as well) does not display any
output with pixel clocks <= 75 MHz. It works with clocks >= 76 MHz.

I'm trying to get more info about this.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com