linux-kernel - Re: Re: Re:[PATCH] drm/panel-edp: Add BOE NV140FHM-N4Z panel entry

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Message-ID: <CAD=FV=WHvSn1ZLHXvkmsic1xyryYYhnTAFNUeNRYjN-JdR5jRA@mail.gmail.com>
Date: Wed, 15 Jan 2025 09:51:15 -0800
From: Doug Anderson <dianders@...omium.org>
To: Andy Yan <andyshrk@....com>
Cc: quic_jesszhan@...cinc.com, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, neil.armstrong@...aro.org, tzimmermann@...e.de, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: Re: Re:[PATCH] drm/panel-edp: Add BOE NV140FHM-N4Z panel entry

Hi,

On Wed, Jan 15, 2025 at 2:15 AM Andy Yan <andyshrk@....com> wrote:
>
>
> Hi Doug,
>
> 在 2025-01-15 00:44:41，"Doug Anderson" <dianders@...omium.org> 写道：
> >Hi,
> >
> >On Tue, Jan 14, 2025 at 1:05 AM Andy Yan <andyshrk@....com> wrote:
> >>
> >>
> >> Hi All,
> >>
> >> At 2025-01-13 18:17:38, "Andy Yan" <andyshrk@....com> wrote:
> >> >
> >> >Sorry, please don't merge this patch. after further testing,
> >> >I found that there are still some changce, it can't read edid.
> >>
> >> It turns out that we need set hpd-reliable-delay-ms = 120 in dts to ensure
> >> the right time to access edid.
> >
> >That seems awfully high and feels likely to be a problem with your
> >board design and not the panel. Are you sure HPD is even hooked up
> >properly on your board? Maybe you're missing a pullup/pulldown config
> >somewhere? Would it be better to just specify "no-hpd" and get the
> >full "HPD absent" delay?
> >
> >
> >> So the patch is ok, it is ready for review.
> >>
> >> >
> >> >At 2025-01-13 16:59:54, "Andy Yan" <andyshrk@....com> wrote:
> >> >>Add an eDP panel entry for BOE NV140FHM-N4Z.
> >> >>
> >> >>No datasheet found for this panel.
> >
> >I seem to be able to find a datasheet for something that calls itself
> >NV140FHM-N4Z, but it might be a different HW version since it has a
> >different ID. In my datasheet, though, "prepare_to_enable" should be
> >80 for this panel, not 200. That matches another nearby panel
> >"NV140WUM-N41". Are you sure you need 200?
>
> I am not sure about that value,
> I searched on the internet, and can't find a datasheet match BOE NV140FHM-NZ
> I set this value according: NV140FHM-N41, and then do many tests to see if it has
> any problem.
>
> http://www.tfinno.com/PIC/PIC/20215121628440.pdf
>
> [    3.021700] panel-simple-dp-aux aux-fded0000.edp: Detected BOE NV140FHM-NZ (0x0b09)

Thanks for the pointer. I will note that the datasheet there shows:

200ms < T3+T4+T5+T6+T8

This is different than I saw in my datasheet, which said:

T4+T5+T6+T8>80ms

Specifically, your time includes T3 and mine doesn't. That's
important. If you want to add support based on your datasheet then the
200ms should be in `powered_on_to_enable`, not in `prepare_to_enable`.

Said another way, you have:

delay_200_500_e50_p2e200

If you want timings based on your datasheet of a similar product:

delay_200_500_e50_po2e200

If you want timings based on my datasheet of a similar product:

delay_200_500_e50_p2e80

I'll let you pick whichever you feel more comfortable with.

-Doug